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XRD98L61
CCD Image Digitizers with CDS, PGA and 12-Bit A/D
May 2001-2
FEATURES * 12-Bit Resolution ADC * 20MHz Sampling Rate * 10-Bit Programmable Gain: 0dB to 36dB PGA * Digitally Controlled Offset-Calibration with Pixel Averager and Hot Pixel Clipper * Widest Black Level Calibration Range at Maximum Gain * DNS Filter Removes Black Level Digital Noise * Manual Control of Offset DAC via Serial Port for use with High-speed Scanners * 1ns/step Programmable Aperture Delay on SPIX, SBLK and ADCLK Sampling Clocks * Single 2.7V to 3.6V Power Supply * Optimized Power Consumption down to 125mW with External Resistor * Low Power for Battery Operation * Two Serially Controlled 8-Bit D/A Converters * * * * 0.1mA Stand-by Mode Current Three-state Digital Outputs 2,000V ESD Protection 48-Pin TQFP Package
APPLICATIONS * Mega-pixel Digital Still Cameras * * * * * * * * * Digital Camcorders 3-CCD Professional/Broadcast Camera Line Scan Cameras PC Video Cameras CCTV/Security Cameras Industrial/Medical Cameras 2D Bar Code Readers High Speed Scanners Digital Copiers
GENERAL DESCRIPTION The XRD98L61 is a complete, low power CCD Image Digitizer for digital motion and still cameras. The product includes a high bandwidth differential Correlated Double Sampler (CDS), 10-bit digitally Programmable Gain Amplifier (PGA), 12-bit Analog-to-Digital Converter (ADC) and improved digitally controlled black level auto-calibration circuitry with programmable pixel averager, hot pixel clipper, and a DNS filter. Two 8-bit serial controlled digital-to-analog converter (DACs) are provided to control external analog signals (Iris, Focus, Flash, etc.) The Correlated Double Sampler (CDS) subtracts the CCD output signal black level from the video level. Common mode signal and power supply noise are rejected by the differential CDS input stage. The PGA is digitally controlled with 10-bit resolution on a linear dB scale, resulting in a gain range of 0dB to 36dB with 0.047dB per LSB of the gain code. The auto calibration circuit compensates for any internal offset of the XRD98L61 as well as black level offset from the CCD. The PGA and black level auto-calibration are controlled through a simple 3-wire serial interface. The timing circuitry is designed to enable users to select a wide variety of available CCD and image sensors for their applications. Readback of the serial data registers is available from the digital output bus. The XRD98L61 has direct access to the ADC and PGA inputs for digitizing other analog signals. The XRD98L61 is packaged in 48-lead TQFP to reduce space and weight, and is suitable for hand-held and portable applications.
ORDERING INFORMATION
Operating Power Supply 3.0V Maximum Sampling Rate 20 MSPS
Part No. XRD98L61AIV
Package 48-Pin TQFP
Temperature Range -40C to 85C
Rev. 2.00
EXAR Corporation, 48720 Kato Road, Fremont, CA 94538 * (510) 668-7000 * FAX (510) 668-7017 * www.exar.com
XRD98L61
ADCinP ADCinN Test1 Test2 CapN CapP Rext ExtRef
AVDD
AGND
Bias
PGA[9:0]
CCDin CDS REFin Fsync CLAMP CAL SPIX SBLK ADCLK + PGA + 12-bit ADC Reg
RBenable
OVDD OVER DB[11:0]
Readback data from Serial Interface
OGND
Timing Logic
Manual DAC Control
Black Level Offset Calibration Loop
CDAC
SDI SCLK LOAD
Serial Interface
Offset Calibration Logic
PGA[9:0] Readback data to output mux DGND DGND
FDAC
Digital Noise Suppression Filter
8 bit DAC 8 bit DAC
DAC0
DAC1
DVDD
DVDD
DGND
PD
RESET
OE
Figure 1. XRD98L61 Block Diagram
AVDD DAC0 DAC1 AGND Test2 Test1 AVDD CCDin REFin AGND RESET PD
36 35 34 33 32 31 30 29 28 27 26 25
PIN CONFIGURATION
ADCinP ADCinN ExtRef CapP CapN AGND AVDD OVER DB11 DB10 DB9 DB8
37 38 39 40 41 42 43 44 45 46 47 48
XRD98L61
24 23 22 21 20 19 18 17 16 15 14 13
OE SDI LOAD SCLK AGND AVDD DGND DVDD ADCLK SPIX SBLK CLAMP
1 2 3 4 5 6 7 8 9 10 11 12
Figure 2. XRD98L61 Pinout Rev. 2.00
2
DB7 DB6 DB5 OGND OVDD DB4 DB3 DB2 DB1 DB0 Test3 CAL
XRD98L61
PIN DESCRIPTION
Pin # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 Symbol DB7 DB6 DB5 OGND OV D D DB4 DB3 DB2 DB1 DB0 Test3 CAL CLAMP SBLK SPIX ADCLK DV D D DGND AVD D AGND SCLK LOAD SDI OE PD RESET AGND REFin CCDin AVD D Test1 Test2 AGND DAC1 DAC0 AVD D ADCinP ADCinN ExtRef CapP CapN AGND AVD D OVER DB11 DB10 DB9 DB8 Type Digital Out Digital Out Digital Out Ground Power Digital Out Digital Out Digital Out Digital Out Digital Out Digital In Digital In Digital In Digital In Digital In Digital In Power Ground Power Ground Digital In Digital In Digital In Digital In Digital In Digital In Ground Analog Analog Power Analog Analog ground Analog Analog Power Analog Analog Analog Analog Analog Ground Power Digital Out Digital Out Digital Out Digital Out Digital Out Description ADC Output ADC Output ADC Output Digital Output Ground Digital Output Power Supply (must be < AV D D ) ADC Output ADC Output ADC Output ADC Output ADC Output (LSB) Test Pin. Connect to DV D D . Calibration Control (clamp OB) DC-Restore Clamp Control Sample Black CDS Clock Sample Pixel CDS Clock ADC Clock On chip Logic Power Supply (must = AV D D ) On chip Logic Ground Analog Power Supply Analog Ground Serial Interface Shift Clock Serial Interface Data Load Serial Interface Data Input Output Enable Control 1=enable, 0=high-Z Power Down Control 1=powerdown, 0=convert Reset Control 1=reset, 0=convert Analog Ground CCD Reference Signal CCD Input Signal Analog Power Supply Direct PGA Input (inverting input) Direct PGA Input (non-inverting input) Analog Ground Utility DAC 1 Output Utility DAC 0 Output Analog Power Supply Direct ADC Input (non-inv erting input) Direct ADC Input (inverting input) External Reference Resistor to Ground (R E X T ) ADC Reference By-Pass ADC Reference By-Pass Analog Ground Analog Power Supply ADC Out of Range Bit ADC Output (MSB) ADC Output ADC Output ADC Output
Rev. 2.00
3
XRD98L61
DC ELECTRICAL CHARACTERISTICS - XRD98L61 Unless otherwise specified: OVDD = DVDD =AVDD = 3.0V, Pixel Rate = 20MSPS, TA = 25C Rext= 30 KOhm
Symbol Parameter Min. Typ. Max. Unit Conditions
CDS Performance CDSVIN VDARK Vrst rCLAMP AVMIN AVMAX PGA n PGA Step Input Range Maximum Dark Voltage Offset Reset Pulse Clamp On Resistance 80 250 500 800 mVPP mV mV +1.0 39.5 dB dB Bits dB Gain Code = 0
G a in C o d e > 768
Pixel (VBLK - VVIDEO), (See Figure 2) At any gain. (See Figure 2)
PGA Parameters Minimum Gain Maximum Gain Resolution Gain Step Size -1.0 32.5 0 36 10 0.047
Transfer function is linear steps in dB
ADC Parameters (Measured in ADC Test Mode)SDI = 0010 001 0011 1000 ADC n fs DNL VID VREF Resolution Max Sample Rate Differential Non-Linearity Full Scale Differential Input 12 20 -1.0 +0.75 +1.0 +1.0 Bits MSPS LSB V CapP - CapN = VREF
ADC Reference Voltage
1
V
DAC Parameters DACn VMAX VMIN tS RL Resolution Vout Max Vout Min Settling Time Output Load 20 8 2.25 0.25 5 Bits Volt Volt Guaranteed Monotonic
ms
KOhm Buffer is needed for resistive load <20K
Rev. 2.00
4
XRD98L61
DC ELECTRICAL CHARACTERISTICS - XRD98L61 (CONT'D) Unless otherwise specified: OVDD = DVDD =AVDD = 3.0V, Pixel Rate = 20MSPS, TA = 25C Rext= 30KOhm
Symbol Parameter Min. Typ. Max. Unit Conditions
System Specifications DNLS en MAXAV en MINAV Latency System DNL Input Referred Noise, Max.Gain Input Referred Noise, Min.Gain Pipeline Delay -1.0 +0.75 +1.0 180 800 7.5 LSB Vrms Vrms cycles No missing codes, monotonic Gain Code = 768 (36db) Gain Code = 0 (0dB)
Digital Inputs (Digital Input Thresholds are Set by DVDD) VIH VIL IIH IIH IIL IIL IIL / IIH CIN Digital Outputs VOH VOL IOZ Digital Output High Voltage Digital Output Low Voltage High-Z Leakage -1
OVDD-0.5
Digital Input High Voltage Digital Input Low Voltage Input Leakage, P/D & Reset Input Leakage, OE Input Leakage, P/D & Reset Input Leakage, OE Input Leakage, All Other Inputs Input Capacitance
2.5 0.5 20 -.50 -.50 -40 -100 40 0 0 -5 10 5 100 .50 .50 0 100
V V A A A A Input = VDD Input = VDD Input = GND Input = GND Input = VDD or GND
nA
pF
V 0.5 +1 V A
While sourcing 2mA While sinking 2mA OE = 0 or PD = 1
Rev. 2.00
5
XRD98L61
DC ELECTRICAL CHARACTERISTICS - XRD98L61 (CONT'D) Unless otherwise specified: OVDD = DVDD =AVDD = 3.0V, Pixel Rate = 20MSPS, TA = 25C Rext=30KOhm
Symbol Parameter Min. Typ. Max. Unit Conditions
Digital I/O Timing tDL tPW1 tPW2 tPIX tBK tVD tSCLK tSET tHOLD tL1 tL2 AVDD DVDD OVDD IDD IDDPD Data Valid Delay Pulse Width of SPIX Pulse Width of SBLK Pixel Period Sample Black (SBLK), Aperture Delay Sample Video (SPIX), Aperture Delay Shift Clock Period Shift Register Setup Time Shift Register Hold Time Load Set-up Time Load Hold Time 10 0 10 10 50 4 4 7 7 100 10 0 10 10 12 ns ns ns ns ns ns ns ns ns ns ns 10 pF load
Power Supplies Analog Supply Voltage Digital Supply Voltage Digital Output Supply Voltage Supply Current Power Down Supply Current 2.7 2.7 2.7 3.0 3.0 3.0 42 0.01 0.1 3.6 3.6 3.6 V V V mA mA Set DVDD = AVDD OVDD < AVDD OVDD = AVDD = DVDD =3.0V, Includes Reference Current. PD = 1
Rev. 2.00
6
XRD98L61
OB Pixel V Dark
Active Pixel VBlack
CCD Waveform
VVideo
Figure 3. Definition of terms for VOut of the CCD waveform: CDSVIN = (VBlack - VVideo)
ABSOLUTE MAXIMUM RATINGS (TA = +25C unless otherwise noted)1, 2, 3 VDD to GND ................................................ +6.6V VRT & VRB ................................ VDD +0.5 to GND -0.5V VIN ............................................... VDD +0.5 to GND -0.5V All Inputs .......................... VDD +0.5 to GND -0.5V All Outputs ........................ VDD +0.5 to GND -0.5V Storage Temperature ........................ -65C to 150C Lead Temperature (Soldering 10 seconds) ...... 300C Maximum Junction Temperature ................... 150C Package Power Dissipation Ratings (TA= +70C) TQFP ...................................... qJA = 105C/W ESD ..................................................... 2000V
Notes:
1 Stresses above those listed as "Absolute Maximum Ratings" may cause permanent damage to the device. This is
a stress rating only and functional operation at or above this specification is not implied. Exposure to maximum rating conditions for extended periods may affect device reliability.
2 Any input pin which can see a value outside the absolute maximum ratings should be protected by Schottky diode
clamps from input pin to the supplies. All inputs have protection diodes which will protect the device from short transients outside the supplies of less than 100mA for less than 100s.
3V DD refers to AVDD, OVDD and DV DD. GND refers to AGND, OGND and DGND.
Rev. 2.00
7
XRD98L61
SERIAL INTERFACE The XRD98L61 uses a three wire serial interface (LOAD, SDI & SCLK) to access the programmable features and controls of the chip. The serial interface uses a 16-bit shift register. The first 6 bits shifted in are the address bits; the next 10 bits are the data bits. The address bits select which of the internal registers will receive the 10 data bits. The interface will only load data from the shift register into the register array if there are exactly 16 rising edges of SCLK while LOAD is low. If more or less rising edges are present, the data is discarded. There is no checking of the address bits to ensure a valid register is written to. If the address bits select an undefined register, the data will be discarded. There is a readback function (see Serial Interface Readback section), which outputs the contents of a selected register on pins DB[11:2] of the digital output bus. The following is the procedure for writing to the serial interface: 1) Force LOAD pin low to enable the shift register. 2) Shift in 16 bits, 6 address bits (msb first), followed by 10 data bits (msb first). 3) Force LOAD pin high to transfer data from the shift register to the serial interface register array.
Note: There must be exactly 16 rising edges of SCLK while LOAD is low.
LOAD
t L1 SCLK t set SDI A5 A4 t hold A3 A2
t SCLK
tL2
MSB A1 A0 D9 D8 D7 D6 D5 D4 D3 D2 D1
LSB D0
t1
t2
...
t15
t16
Time
Figure 4. Serial Interface Timing Diagram
Rev. 2.00
8
XRD98L61
LSB SDI D0 SCLK D1 D2 D3
Data Bits D4 D5 D6 D7 D8
MSB
Address Bits A0 A1 A2 A3 A4 A5
D9
Data Input Register Select LOAD Register Array Read Back Output Bus to DB[11:2] Address Decoder
Figure 5. Serial Interface Block Diagram
Rev. 2.00
9
XRD98L61
Address bits
Reg. Name A5 A4 A3 A2 A1 A0 Gain Offset Calibration Wait A Wait B OB Lines CDAC FDAC Control Polarity Clock Delay A Delay B DAC0 DAC1 000000 000001 000010 000011 000100 000101 000110 000111 001000 001001 001010 001011 001100 001101 001110
CLKtest 0 Nullamp CMtest Fastclk 0 0 0 DelayA[8] DelayA[7] DelayA[6] 0 0 0 DelayB[8] DelayB[7] DelayB[6] 0 0 0 DAC0[7] DAC0[6] 0 0 DAC1[7] DAC1[6] 0 0 FDAC[9] 0 DIGtest 0 CDAC[8] 0 FDAC[8] 0 ADCtest 0 OBL[7] 0 CDAC[7] 0 FDAC[7] 0 NoCDS 0 OBL[6] 0 CDAC[6] 0 FDAC[6] 0 LowPwr 0 OBL[5] 0 CDAC[5] 0 FDAC[5] 0 OE 1 SBLKpol 0 CLAMPopt 0 DelayA[5] 0 DelayB[5] 0 DAC0[5] 0 DAC1[5] 0 OBL[4] 0 CDAC[4] 0 FDAC[4] 0 DAC1pd 1 SPIXpol 0 OneShot 0 DelayA[4] 0 DelayB[4] 0 DAC0[4] 0 DAC1[4] 0 OBL[3] 0 CDAC[3] 0 FDAC[3] 0 DAC0pd 1 CALpol 0 ClampCal 0 DelayA[3] 0 DelayB[3] 0 DAC0[3] 0 DAC1[3] 0 OBL[2] 0 CDAC[2] 0 FDAC[2] 0 AFEpd 0 CLAMPpol 0 SPIXopt 0 DelayA[2] 0 DelayB[2] 0 DAC0[2] 0 DAC1[2] 0 Avg[2] 1 WL[11] 0 Avg[1] 0 WL[10] 0
Data bits
D9
PGA[9] 0
D8
PGA[8] 0
D7
PGA[7] 0 OB[7] 1 Avg[0] 1 WL[9] 0
D6
PGA[6] 0 OB[6] 0 Mode 0 WL[8] 0
D5
PGA[5] 0 OB[5] 0 LFrame 0 WL[7] 0
D4
PGA[4] 0 OB[4] 0 DNS[1] 1 WL[6] 0
D3
PGA[3] 0 OB[3] 0 DNS[0] 1 WL[5] 0
D2
PGA[2] 0 OB[2] 0 FastCal 1 WL[4] 0
D1
D0
PGA[1] PGA[0] 0 0 OB[1] OB[0] 0 0 Hold ManCal 0 0 WL[3] WL[2] 0 0 WL[1] WL[0] 0 1 OBL[1] OBL[0] 1 0 CDAC[1] CDAC[0] 0 0 FDAC[1] FDAC[0] 0 0 ADCpd PwrDwn 0 0 *Reserved ADCpol 0 0 RSTreject VSreject 0 0 DelayA[1] DelayA[0] 0 0 DelayB[1] DelayB[0] 0 0 DAC0[1] DAC0[0] 0 0 DAC1[1] DAC1[0] 0 0
ReadBack Reset
111110 111111
RBenable RBreg[8] 0 0
RBreg[7] 0
RBreg[6] 0
RBreg[5] RBreg[4] 0 0
RBreg[3] 0
RBreg[2] 0
RBreg[1] 0
RBreg[0] 0 Reset 0
Table 1. Serial Interface Register Address Map & default values
D9 PGA[9] 0 D8 PGA[8] 0 D7 PGA[7] 0 D6 PGA[6] 0 D5 PGA[5] 0 D4 PGA[4] 0 D3 PGA[3] 0 D2 PGA[2] 0 D1 PGA[1] 0 D0 PGA[0] 0
Gain Default
Gain Register (Reg. 0, Address 000000) The Gain register is used to set the gain of the Programmable Gain Amplifier (PGA). Code 0000000000 is minimum gain (0 dB). Codes 1011111111 and greater are maximum gain (36 dB). See the Programmable Gain Amplifier (PGA) section for more information.
D9 Offset Default 0 D8 0 D7 OB[7] 1 D6 OB[6] 0 D5 OB[5] 0 D4 OB[4] 0 D3 OB[3] 0 D2 OB[2] 0 D1 OB[1] 0 D0 OB[0] 0
Offset Register (Reg. 1, Address 000001) The Offset register is used to set the target ADC output code for Optical Black pixels. See the Black Level Offset Calibration section for more information.
NOTE: *Reserved Test register bit. Used for factory test only. Please do not modify.
Rev. 2.00
10
XRD98L61
D9 Avg[2] 1 D8 Avg[1] 0 D7 Avg[0] 1 D6 Mode 0 D5 LFrame 0 D4 DNS[1] 1 D3 DNS[0] 1 D2 FastCal 1 D1 Hold 0 D0 ManCal 0
Calibration Default
Calibration Register (Reg. 2, Address 000010) The Calibration register is used to set various options for the Black Level Offset Calibration. Avg[2:0] set the number of OB pixels to average: 000 = 4 pixels (not recommended) 100 = 64 pixels 001 = 8 pixels (not recommended) 101 = 128 pixels (default) 010 = 16 pixels (not recommended) 110 = 256 pixels 011 = 32 pixels 111 = 512 pixels Mode=0, selects Line mode calibration (use OB pixels at start or end of each line). Mode=1, do not use. LFrame=0, selects Line mode calibration. LFrame=1, do not use. DNS[1:0] selects the Digital Noise Suppression filter setting: 00 = off, 10 = medium, 01 = narrow, 11 = wide. FastCal=0, disables speedup convergence option of the calibration feedback loop. FastCal=1, enables an option to speedup convergence of the calibration feedback loop. Hold=0, normal operation of calibration feedback loop. Hold=1, stops all updates to the Coarse and Fine offset DAC accumulators. ManCal=0, normal operation of calibration feedback loop. ManCal=1, enables manual calibration. The offset DACs are set to the values in the CDAC and FDAC registers. See the Black Level Offset Calibration section for more information.
D9 WL[11] 0 D8 WL[10] 0 D7 WL[9] 0 D6 WL[8] 0 D5 WL[7] 0 D4 WL[6] 0 D3 WL[5] 0 D2 WL[4] 0 D1 WL[3] 0 D0 WL[2] 0
WaitA Default
WaitA Register (Reg. 3, Address 000011)
D9 WaitB Default 0 D8 0 D7 0 D6 0 D5 0 D4 0 D3 0 D2 0 D1 WL[1] 0 D0 WL[0] 1
WaitB Register (Reg. 4, Address 000100) The WaitA and WaitB registers are concatenated to make up the Wait register. See OB Pixel calibration section for more information.
D9 OB Lines Default 0 D8 0 D7 OBL[7] 0 D6 OBL[6] 0 D5 OBL[5] 0 D4 OBL[4] 0 D3 OBL[3] 0 D2 OBL[2] 0 D1 OBL[1] 1 D0 OBL[0] 0
OB Lines Register (Reg. 5, Address 000101) The OB Lines register is used by the Offset Calibration Logic to set the number of Optical Black lines used for Calibration in the Frame Mode. Do not use. Rev. 2.00
11
XRD98L61
D9 CDAC Default 0 D8 D7 D6 D5 D4 D3 D2 D1 D0 CDAC[8] CDAC[7] CDAC[6] CDAC[5] CDAC[4] CDAC[3] CDAC[2] CDAC[1] CDAC[0] 0 0 0 0 0 0 0 0 0
CDAC Register (Reg. 6, Address 000110) The CDAC register is used to set the Coarse Offset DAC in the Manual Calibration mode. See Calibration Option, in the Black Level Offset Calibration section for more information.
D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 FDAC FDAC[9] FDAC[8] FDAC[7] FDAC[6] FDAC[5] FDAC[4] FDAC[3] FDAC[2] FDAC[1] FDAC[0] Default 0 0 0 0 0 0 0 0 0 0
FDAC Register (Reg. 7, Address 000111) The FDAC register is used to set the Fine Offset DAC in the Manual Calibration mode. See Calibration Option, in the Black Level Offset Calibration section for more information.
D9 D8 D7 D6 DIGtest ADCtest NoCDS LowPwr 0 0 0 0 D5 OE 1 D4 D3 DAC1pd DAC0pd 1 1 D2 AFEpd 0 D1 D0 ADCpd PwrDwn 0 0
Control Default
Control Register (Reg. 8, Address 001000) The Control register is used to set various test and power-down modes. DIGtest=0, normal operation. DIGtest=1, Exar test mode - do not use. ADCtest=0, connects PGA output to ADC input. ADCtest=1, connects ADCinP & ADCinN pins to ADC input. NoCDS=0, connects CDS output to PGA input. NoCDS=1, connects Test1 & Test2 pins to PGA inputs (CDS by-pass mode). Low Power=0, normal operation. Low Power=1, Exar test mode - do not use. OE=0, digital outputs in high-Z state. OE=1, digital outputs enabled. DAC1pd=1, Utility DAC1 is powered down. DAC0pd=1, Utility DAC0 is powered down. AFEpd=0, normal operation. AFEpd=1, CDS & PGA are powered down, do not use. ADCpd=0, normal operation. ADCpd=1, ADC is powered down, do not use. PwrDwn=0, normal operation. PwrDwn=1, the whole chip is powered down. Rev. 2.00
12
XRD98L61
D9 Polarity Default 0 D8 0 D7 0 D6 0 D5 D4 D3 D2 D1 D0 SBLKpol SPIXpol CALpol CLAMPpol *Reserved ADCpol 0 0 0 0 0 0
Polarity Register (Reg. 9, Address 001001) The Polarity register is used to set the polarity for the 6 input clock signals. For each clock: polarity bit=0 sets clock active low, polarity bit=1 sets clock active high.
D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 CLKtest Nullamp CMtest Fastclk CLAMPopt Oneshot ClampCal SPIXopt RSTreject VSreject 0 0 0 0 0 0 0 0 0 0
Clock Default
Clock Register (Reg. 10, Address 001010) The Clock register is used to set various clocking options. CLKtest=0, Normal operation. CLKtest=1, Exar test mode - Do not use. Nullamp=0, Normal operation. Nullamp=1, Exar test mode - Do not use. CMtest=0, Normal operation. CMtest=1, Exar test mode - Do not use. Fastclk=0, Normal operation. Fastclk=1, Exar test mode - Do not use. CLAMPopt=0, DC Restore bias is on only during CLAMP. CLAMPopt=1, DC Restore bias is always ON. OneShot=0, CAL defines OB pixels. Clamp controls DC restore. OneShot=1, CAL controls DC restore and defines OB pixels. CLAMP used for VS reject. ClampCal=0, CLAMP at start of line, CAL at end of line (affects VS reject). ClampCal=1, CAL at start of line, CLAMP at end of line (affects VS reject). SPIXopt=0, 2 starts DelayA[5:3] + DelayB[8:6] after SBLK trailing edge SPIXopt=1, 2 starts DelayB[2:0] after SPIX pin leading edge. RSTreject=0, Reset reject switch (3) not clocked, always on. RSTreject=1, Reset reject switch (3) clocked. VSreject=0, Vertical Shift Reject is inactive. VSreject=1, Vertical Shift Reject is active.
NOTE: *Reserved Test Register bit. Used for factory test only. Please do not modify.
Rev. 2.00
13
XRD98L61
D9 Delay A Default 0 D8 D7 D6 D5 D4 D3 D2 D1 D0 DelayA[8] DelayA[7] DelayA[6] DelayA[5] DelayA[4] DelayA[3] DelayA[2] DelayA[1] DelayA[0] 0 0 0 0 0 0 0 0 0
Delay A Register (Reg. 11, Address 001011)
D9 Delay B Default 0 D8 D7 D6 D5 D4 D3 D2 D1 D0 DelayB[8] DelayB[7] DelayB[6] DelayB[5] DelayB[4] DelayB[3] DelayB[2] DelayB[1] DelayB[0] 0 0 0 0 0 0 0 0 0
DelayB Register (Reg. 12, Address 001100) The DelayA & DelayB registers are used to add internal delay to the pixel rate clocks. For each 3 bit delay parameter, 000 is minimum delay, 111 is maximum delay (7ns). DelayA[8:6]: ADC Clock delay. DelayA[5:3]: 1 trailing edge delay. DelayA[2:0]: 1 leading edge delay. DelayB[8:6]: Delay for SPIX option. DelayB[5:3]: 2 trailing edge delay. DelayB[2:0]: 2 leading edge delay.
D9 DAC0 Default 0 D8 0 D7 D6 D5 D4 D3 D2 D1 D0 DAC0[7] DAC0[6] DAC0[5] DAC0[4] DAC0[3] DAC0[2] DAC0[1] DAC0[0] 0 0 0 0 0 0 0 0
DAC0 Register (Reg. 13, Address 001101)
D9 DAC1 Default 0 D8 0 D7 D6 D5 D4 D3 D2 D1 D0 DAC1[7] DAC1[6] DAC1[5] DAC1[4] DAC1[3] DAC1[2] DAC1[1] DAC1[0] 0 0 0 0 0 0 0 0
DAC1 Register (Reg. 14, Address 001110) The DAC1 & DAC0 registers are used to program the two 8-bit Utility DACs. Code 00000000 is minimum output voltage. Code 11111111 is maximum output voltage.
Rev. 2.00
14
XRD98L61
D9 ReadBack RBenable Default 0 D8 D7 D6 D5 D4 D3 D2 D1 D0 RBreg[8] RBreg[7] RBreg[6] RBreg[5] RBreg[4] RBreg[3] RBreg[2] RBreg[1] RBreg[0] 0 0 0 0 0 0 0 0 0
Readback Register (Reg. 62, Address 111110) The readback register is used to enable the readback function and select a register for readback. RBenable=0, Readback disabled. RBenable=1, Readback enabled. Contents of selected register is output on DB[11:2] pins. RBreg[8:0], select register to read from, see table in Serial Interface Read Back section.
D9 Reset Default 0
D8 0
D7 0
D6 0
D5 0
D4 0
D3 0
D2 0
D1 0
D0 Reset 0
Reset Register (Reg. 63, Address 111111) The Reset register is used to reset the entire chip. Reset=0, Normal operation. Reset=1, Resets the chip. The Reset bit will automatically reset after approximately 10 ns delay.
Rev. 2.00
15
XRD98L61
SERIAL INTERFACE READ BACK The readback function is used to view the content of the serial interface registers as well as several key registers in the calibration logic. Readback is enabled by writing a 1 to the RBenable bit of the Readback register, bit D9 of register 62. In the readback mode, the content of the selected register is output on the 10 MSBs of the ADC output bus pins DB[11:2]. As long as valid clocks and CCD signal are applied, the calibration will continue to function properly during readback (internally the ADC data is still sent to the calibration logic). Registers are selected for readback by writing to the RBreg[8:0] bits in the Readback register, bits D8 to D0 of register 62. If RBreg[8:6]=000, then RBreg[5:0] are used to address the serial interface registers. Currently only register addresses 0 to 14, 62 and 63 are defined. If RBreg[8:6]000, then RBreg[5:0] are ignored and RBreg[8:6] are used to address registers in the calibration logic. Currently only three calibration registers are accessible.
RBenable RBreg 8 0 x 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0
RBreg RBreg RBreg Rbreg 7 6 5 4 x x x x 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 1 1 0 1 x x 1 0 x x 1 1 x x
RBreg RBreg 3 2 x x 0 0 0 0 0 0 0 0 0 1 0 1 0 1 0 1 1 0 1 0 1 0 1 0 1 1 1 1 1 1 1 1 1 1 x x x x x x
RBreg RBreg Selected Register 1 0 x x none (ADC data output) 0 0 Gain 0 1 Offset 1 0 Calibration 1 1 Wait A 0 0 Wait B 0 1 OB Lines 1 0 CDAC 1 1 FDAC 0 0 Control 0 1 Polarity 1 0 Clock 1 1 Delay A 0 0 Delay B 0 1 DAC0 1 0 DAC1 1 0 ReadBack 1 1 Reset x x FDAC output from Cal. logic x x CDAC output from Cal. logic x x Avg. output from Cal logic
Table 2. Read-back Register Selection
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CORRELATED DOUBLE SAMPLE/HOLD (CDS) The function of the CDS block is to sense the voltage difference between the black level and video level for each pixel. The PGA then amplifies this difference to the desired level for the ADC. The CDS and PGA are fully differential. The CCDin pin should be connected, via a capacitor, to the CCD output signal. The REFin pin should be connected, via a capacitor, to the CCD "Common" voltage (typically the CCD ground is used as the "Common" voltage). These capacitors, C1 and C2, are typically 0.01F + 10% or better matching. The timing for the switches shown in Figure 6 are determined by 1, 2, and 3. 1, 2, and 3 are internally generated from the timing signals SBLK and SPIX shown in Figures 17 & 18. 3 (reset reject switches) are closed to simplify the operation described below. At the beginning (or end) of every video line, the DC restore switch forces one side of the external capacitors to an internal bias level (Vbias1=1.2V). The DC restore switch is controlled by the combination of the CLAMP input signal ANDed with the 2 clock. During the black reference phase of each CCD pixel, the 1 (Sample Black Reference) switches are turned on, shorting the PGA1 inputs to a second bias level (Vbias2). The Coarse Offset DAC adds an adjustment to the bias level (Vbias2) to cancel black level offset in the CCD signal. When the 1 switches turn off, the pixel black reference level is sampled on the internal black sample capacitors, and the PGA is ready to gain up the CCD video signal. During the video phase of each CCD pixel, the difference between the pixel black level and video level is transmitted through the internal black sample capacitors and converted to a fully differential signal by the PGA1 amplifier. At this time, the 2 (Sample Pixel value) switches turn on, and the internal video sample capacitors track the amplified difference. The Fine Offset DAC adds offset adjustment to the PGA2 output (post gain).
Vbias2
CDS
External DC Blocking Capacitors
PGA
1
Coarse Offset DAC
CCDin CCD C1 REFin C2
3
2
Fine Offset DAC
Internal Black Sample Capacitors
PGA1
PGA2
CLAMP 2 DC Restore Switches Vbias1=1.2V
Internal Video Sample Capacitors
Figure 6. CDS and PGA Block Diagram Rev. 2.00
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XRD98L61
4.0 Programmable Gain Amplifier (PGA) The PGA provides gains from 0dB to 36 dB in approximately 0.047 dB steps. The desired gain setting is programmed via the 10 bit gain register in the Serial Interface. For gain codes between 0 and 767, the gain can be calculated by the following equation: For gain codes 768, the gain is fixed at 36 dB. The gain doubles every 128 codes to simplify DSP algorithms and control.
Code Gain[ dB] = x 36 768
36
30 27 PGA Gain [dB] 24
18
12 9 6
0 192 256 512 568 768 0 1024
Gain Code, PGA[9:0]
Figure 7. PGA Gain vs. Gain Code An example of setting the gain is as follows: If the CCD input is limited by 800mVpp (CDSVIN) and the ADC full scale differential input (VID) is 2Vpp, then a minimum gain is calculated by:
VID = 20 log 2 = 8dB Gain = 20 log CDSV IN 0.8
The gain code would be set to 170d for 8dB of PGA gain.
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XRD98L61
DIRECT PGA INPUT MODE The inputs to the PGA can be accessed directly (bypassing the CDS) through the Test1 & Test2 pins (See Figure 1). The test inputs require Test2 set to a dc voltage of 1.2V and the Test1 input signal between 1.2V and 0.4V. ADC Zero Scale (000h) is at 1.2V input and Full Scale (FFFh)for a 0.4V input assuming a gain of 8dB. (ADC full scale input is 2Vpp.) To enable the Direct PGA Input mode, write a "1" to the NoCDS bit in the Control register of the serial interface. This will disconnect the CDS from the PGA input and turn on the switches that connect the Test1 & Test2 pins to the PGA. Note that when the part is not in the NoCDS mode that Test1 and Test2 are grounded through an equivalent 10kohm switch resistance. To avoid shorting the input drive circuitry into Test1 and Test2 to ground, the NoCDS mode must be active before the input signal is driven. In this mode, the SBLK and SPIX clocks must be clocked, due to the switched capacitor architecture of the second PGA stage. ADCLK must be provided to digitize the PGA output. The analog PGA output cannot be monitored; it does not come out to any pin. The calibration logic should be put into the Hold mode, or into the ManCAL mode. The Coarse offset correction DAC (CDAC) is disconnected from the PGA inputs in this mode. The CDAC does not affect the Direct PGA inputs, but the Fine offset correction DAC (FDAC) does affect the PGA output. The FDAC range is +-128mV at the ADC input. FDAC can be used to adjust offset in the system when in the ManCal mode. Note the calibration logic should not be in the automatic mode, because the FDAC circuitry is not "aware" that the Coarse DAC is not active, and thus could cause errors if left operating automatically. Therefore, it is recommended that either CAL Hold or Manual CAL mode be asserted. The DNL in the Direct PGA Input Mode is shown in Figure 26.
Input Sampled (N)
Input Sampled (N+1)
Input Signal Test1
SBLK
PGA tracks Input Signal
SPIX
nonoverlap=4ns
ADCLK
ADC tracks PGA output (N-8) (N-7) (N-6)
DB[11:0]
Figure 8. Direct PGA Input Timing (Default Polarities)
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XRD98L61
ANALOG TO DIGITAL CONVERTER (ADC) The analog-to-digital converter is based on pipeline architecture with a built in track & hold input stage. The track & hold and ADC conversion are controlled by the externally supplied ADCLK. The polarity of the ADCLK is programmable. If ADCpol = low, the track & hold circuit tracks the PGA output while ADCLK is high and holds while ADCLK is low. If ADCpol = high, the track & hold circuit tracks the PGA output while ADCLK is low and holds while ADCLK is high. ADCLK should be a 50% duty cycle clock, and should be synchronized with SBLK such that ADC tracking ends at the same time as the CDS sample black ends. (See Figure 13). The ADC reference levels, CapP & CapN, are generated from an internal voltage reference. To minimize noise, these pins should have high frequency bypass capacitors to AGND. The value of these bypass capacitors will affect the time required for the reference to charge up and settle after power down mode. The ADC output bus, DB[11:0] & OVER, has 3-state capability that is controlled by the OE bit of the Control register. The outputs are enabled when the OE bit is high. The outputs are high impedance when the OE bit is low. Direct ADC Input Mode The ADC inputs can be accessed directly via the ADCinP & ADCinN pins. To enable the Direct ADC Input mode, write a "1" to the ADCtest bit of the Control register. This will disable the CDS/PGS and connect the ADCinP & ADCinN pins directly to the ADC. The ADC data is valid 6.5 clock cycles after the sampling edge of ADCLK (default is falling edge). POWER DOWN The Power Down mode can be activated by forcing the PD pin high, or by writing a "1" to the PwrDwn bit in the Control register. For normal operation, the PD pin must be low and the PwrDwn bit must be "0". In the Power Down mode, all analog circuits are turned off, the calibration is placed in the Hold mode, and the output bus, (DB[11:0] and OVER) is put in the high impedance mode. All the digital registers retain their values, so the PGA gain, offset, and calibration will return to their previous states. The serial interface pins remain active in the Power Down mode. The PD pin and the PwrDwn bit do not reset any internal registers. In addition to the PwrDwn bit, there are 4 other power down bits which only turn off portions of the chip. DAC1pd and DAC0pd control the two 8 bit utility DACs. AFEpd controls the CDS & PGA circuits. ADCpd controls the ADC. AFEpd & ADCpd are included for factory test and characterization purposes; they are not intended for use in digital camera applications. DIGITAL OUTPUT ENABLE CONTROL The digital output bus, DB[11:0] and OVER, has 3state capability. When the OE bit in the control register is high, and the OE Pin (#24) is high, the digital output drivers are enabled and active. When the OE bit is low, or the OE Pin is low, the digital output drivers are disabled and the bus is in the high impedance state. The OE bit and OE Pin only control the digital output drivers; all other circuits on the chip will remain active. The black level calibration can still run properly when the outputs are in the high impedance state. CHIP RESET The chip includes a Power-On-Reset function (POR), so when the power supplies are turned on, the chip will always power up with default values in all registers. There are two methods to force a chip reset. The first is to write a "1" to the RESET bit in the reset register. This will reset the chip, and after a delay of about 10 ns, the reset bit will automatically clear itself. The second reset method is to force the RESET pin high. This will reset the chip until the RESET pin goes low again. The RESET pin has an internal pull down.
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BLACK LEVEL OFFSET CALIBRATION To get the maximum color resolution and dynamic range, the XRD9861 uses a digitally controlled calibration circuit to correct for offset in the CCD signal as well as offset in the CDS, PGA & ADC signal path. This calibration is done while the CCD outputs Optical Black (OB) pixels. In the "Line" timing mode, the OB pixels at the start or end of each scan line are used for calibration.
CCD signal
CDS
+
PGA
+
12-bit ADC
Reg
DB[11:0]
CDAC
FDAC
12
Black Level Offset Calibration Loop ManCAL CDAC, FDAC Wait[11:0] OB Lines[7:0] Coarse Accumulator Fine Accumulator + -
Hot Pixel Clipper
From Serial Interface Registers
Offset Calibration Logic
DNS Filter
+
Pixel Averager
Hold, FastCal DNS[1:0] PGA[9:0] OB[7:0] Avg[2:0]
Figure 9. Black Level Offset Calibration Block Diagram
D9 X X X
D8 X X X
D7 0 0 0
Offset Register D6 D5 0 0 0 0 0 0
X X
X X
1 1
1 1
1 1
D4 0 0 0 . . . 1 1
D3 0 0 0
D2 0 0 0
D1 0 0 1
D0 0 1 0
1 1
1 1
1 1
0 1
ADC Output Black Level (LSB) Do Not Use Do Not Use 2 (Minimum offset code) . . . 254 255
Table 3. Black Level Output Control
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Hot Pixel Clipper CCD's occasionally have hot pixels. These are defective pixels, which always output a bright level. To ensure the Black Level is not affected by hot pixels in the OB area, the Hot Pixel Clipper limits pixel data from the ADC to a maximum value of 511 (1FFh). This clipping only affects the data used by the internal calibration logic. Data on the ADC output bus, DB[11:0], is not clipped.
AVG[2] 0 0 0 0 1 1 1 1 AVG[1] 0 0 1 1 0 0 1 1 AVG[0] 0 1 0 1 0 1 0 1 # of Pixels to Average 4 (Not recommended) 8 (Not recommended) 16 (Not recommended) 32 64 128 (default) 256 512
Table 4. Programming the Pixel Averager Offset Difference Next, the Offset register value, OB[7:0], is subtracted from the OB pixel average. If the difference is positive, the offset DACs are adjusted to reduce the effective ADC output code. If the difference is negative, the offset DACs are adjusted to increase the effective ADC output code. The FAST_CAL and DNS options will affect how the DAC adjustments are made.
4096
Clipper Output
Coarse & Fine Accumulators The Coarse and Fine Accumulators are the registers which hold the digital codes for the Coarse and Fine Offset DACs. The Offset DAC adjustments are made by adding or subtracting to the value in the Fine accumulator. If there is an overflow or underflow in the Fine Accumulator, the Fine Accumulator is reset to its mid-scale value, and the Coarse Accumulator is incremented or decremented accordingly.
511 0 0 511 2048 4096
ADC Data
Figure 10. Hot Pixel Clipper
Pixel Averager After the clipper, the logic takes an average of Optical Black pixels. The number of pixels to be averaged can be selected as one of the following: 4, 8, 16, 32, 64, 128, 256, or 512. The AVG[2:0] bits in the Calibration register are used to program the number of pixels to average. This averaging function filters out noise and prevents image artifacts. The calibration logic will average OB pixels over as many lines as required to get the programmed number of pixels to average.
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CALIBRATION OPTIONS Fast Cal The purpose of this option is to reduce the amount of time required for initial convergence of the calibration feedback system. The feedback system is designed to have a slow response time to avoid introducing image artifacts. The slow response time is achieved by averaging many OB pixels and by limiting the Fine accumulator changes to 1 count at a time (FDAC lsb = 1/2 ADC lsb). The FastCal option maintains this slow response while the difference between the averaged ADC data and the Offset Code is small, but when the difference is larger than 128 lsb's, the coarse accumulator takes a step. The actual step size depends on the PGA Gain code, and is set such that the step will cause no more than a 128 LSB change in the ADC output. To activate the FastCal mode ,write a "1" to the FastCal bit in the Calibration register. By default, the FastCal mode is active.
Offset Adjustment [ADC LSBs]
DNS[1] 0 0 1 1
DNS[0] 0 1 0 1
DNS Filter Width OFF (default) Narrow Medium Wide
Table 5. DNS Threshold Programming To activate the Digital Noise Suppression mode, write to the DNS[1:0] bits in the Calibration register.By default, the Digital Noise Suppression is ON and set to the wide filter width.
Hold Mode The purpose of this mode is to prevent any changes in the Fine or Coarse accumulators. This mode is intended to optimize digital still camera applications (DSC). The idea is to first run the calibration normally so the Fine and Coarse accumulators converge on the correct values to achieve the programmed Offset Code. Then, just before acquiring the final image data, activate the Hold mode. This will ensure the black level offset of the CDS/PGA does not change while the final image is being transferred out of the CCD. Once the image has been acquired from the CCD, turn off the Hold mode so the chip can continue to compensate for any changes in offset due to temperature drift or other effects. To activate the Hold mode, write a "1" to the Hold bit in the Calibration register. By default, the Hold mode is not active.
Fine DAC Steps +0.5 0 -0.5
Coarse DAC steps -128 -1 0 +1 +128 Difference [ADC lsb's]
Figure 11. Calibration in FastCal (Speed Up) Mode Digital Noise Suppression (DNS Filter) The purpose of this option is to eliminate small changes in the Black Level offset by making the calibration system less sensitive to small changes in the measured offset. In this mode, the user has the option of selecting from three filter settings;see Table 5. Rev. 2.00
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XRD98L61
Manual Mode The purpose of this mode is to disable the automatic calibration feature. This allows manual adjustment of offset in applications such as digital copiers and high speed scanners. In Manual mode, the Coarse accumulator is programmed by writing to the CDAC register; the Fine accumulator is programmed by writing to the FDAC register. The Coarse accumulator is a 9 bit register. The Fine accumulator is a 10 bit register. To activate the Manual mode, write a "1" to the ManCal bit in the Calibration register. By default, the Manual mode is not active. OB PIXEL CALIBRATION Line Mode Calibration In the Line mode, OB pixels are sampled when CAL is active. CAL can be programmed to be active high or active low. Please see the Timing section for more details about clock polarity. Averaging will span as many lines as needed to get the number of OB pixels programmed by AVG[2:0]. Updates to the offset DACs occur during the Optical Black pixel time after a complete iteration. A complete iteration includes the pixel clipping, averaging, calculation of the offset difference, and calculation of the DAC update values. After a complete iteration, the averager is reset, and the logic waits for the number of lines programmed in the "Wait A" & "Wait B" registers (WL[11:0]) before starting the next iteration. CLOCK BASICS There are five clock signals: SBLK, SPIX, ADCLK, CLAMP, and CAL. The pixel rate clocks are SBLK, SPIX, and ADCLK. SBLK controls sampling of the Black reference level for each pixel. SPIX controls sampling of the Video level for each pixel. ADCLK controls the ADC sampling the PGA output. Figure 12. Clock Polarity and Aperture Delays CLOCK POLARITY Each of the five clocks has a separate polarity control bit in the Polarity register. If the polarity bit for a clock is low, then the clock is active low. If the polarity bit for a clock is high, then the clock is active high. After reset (by POR, reset bit or reset pin), all clocks default to active low. The line rate clocks are CLAMP & CAL. CLAMP controls the DC restore function for the external AC coupling capacitors. CAL controls the Black level calibration by defining the OB pixels at the start or end of each line. In the One Shot mode (CAL only), CLAMP is used to define the vertical shift period between lines.
SBLK SPIX ADCLK CLAMP CAL
Polarity Aperture Delays Clock Logic AFE
ADC
Calibration
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XRD98L61
PIXEL RATE CLOCKS
tPIX Black Sample Point CCD Signal tBK tVD tPW1 Video Sample Point
SBLK
SPIX
tPW2
ADCLK
tDL DB[11:0]
Note: The timing descriptions in this section are correct for the default conditions: All Polarity bits = 0, RSTreject = 0 (switch always ON), SPIXopt = 0
Figure 13. Detailed Pixel Rate Clock Timing for Default Register Settings
SBLK, SPIX & ADCLK Sampling of the pixel Black Level is controlled by the SBLK pulse. When SBLK is low, the internal sample Black switches in the CDS are ON, sampling the pixel black level on the internal capacitors. The AFE starts tracking the pixel Video Level, an internal delay, after the rising edge of SBLK. The internal delay is programmed by DelayB[8:6]. The AFE holds the pixel Video Level on the rising edge of SPIX. The ADC will track the PGA output when ADCLK is high. The ADC will hold the PGA output and start a conversion when ADCLK goes low. The falling edge of ADCLK should happen coincident with, or just before, the rising edge of SBLK. ADCLK should be as close as possible to 50% duty cycle.
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Pixel N Black Level CCD Signal Sample Black SBLK Sample Video SPIX ADCLK Video Level
Pixel N+1
Sample PGAout Pixel N-8
bit 11
bit 10
bit 9
bit 8
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bits 1&0
Error Correction
tDL Pixel N
DB[11:0]
Pixel N-7
Pixel N-6
Pixel N-5
Pixel N-4
Pixel N-3
Pixel N-2
Pixel N-1
7.5 Pixel Pipeline Delay
Figure 14. Pixel Timing Showing Pipeline Delay
Pipeline Delay The digital outputs, DB[11:0] and OVER, are synchronized to ADCLK. When ADCLKpol=0 (default), the digital outputs change on the rising edge of ADCLK. Figure 14 shows the pipeline delay (latency) from sampling a pixel at the CDS input, until the coresponding data is available at the digital output. SPIXopt In the default case shown in Figure 15, SPIXopt=0, the internal sample video switches turn ON a programmed delay after the SBLK pulse ends, and turn OFF at the end of the SPIX pulse. The turn ON delay is programmed by DelayB[8:6]. When SPIXopt = 1, the internal SPIX switches are controlled only by the SPIX pulse. This mode is intended for camera systems where the designer has the ability to externally fine tune both the rising and falling edges of SPIX to achieve optimum performance (see Figure 16).
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XRD98L61
Black Level CCD Signal Video Level
SBLK SPIX ADCLK DelayB[8:6]
2
Figure 15. Pixel Rate Clock Timing with SPIXopt=0 (Default)
Black Level CCD Signal Video Level
SBLK SPIX ADCLK
2
Figure 16. Pixel Rate Clock Timing with SPIXopt=1
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XRD98L61
Reset Reject Switches Turn OFF Black Level CCD Signal Video Level
SBLK SPIX ADCLK
3
Figure 17. Pixel Rate Clock Timing with RSTreject=1 Reset Reject In the default state, the reset reject switches (3) are always ON, they are not clocked. The reset pulse of each pixel is transmitted to the first stage of the PGA. Depending on the PGA gain and the actual voltage level of the reset pulse, this could cause the first stage of the PGA to rail. During the Black Level sampling, the PGA should have enough time to recuperate, but as a precaution, we have included the Reset Reject option. When RSTreject = 1, the reset reject switches are turned OFF at the end of the SPIX pulse, and turned ON again at the start of the SBLK pulse. This will effectively reject the reset pulse and prevent it from railing the PGA. Aperture Delays One of the most difficult tasks in designing a digital camera is optimizing the pixel timing for the CCD, CDS and ADC. We have included the programmable aperture delay function to help simplify this job. There are two serial interface registers, DelayA & DelayB, used to program the aperture delays. Each register is divided into 3 delay parameters. Each delay parameter is 3 bits wide. Each delay parameter can be set to add from 0ns to 7ns of delay. The delays are added to the clock signals after the polarity control. This means the definition of leading edge and trailing edge depends on the polarity control bit for each clock. For the default case, SBLKpol=0 & Rev. 2.00
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SPIXpol=0, the leading edge is the falling edge and the trailing edge is the rising edge. DelayA[2:0] controls the delay added to the leading edge of SBLK. This positions the falling edge of internal signal 1. DelayA[5:3] controls the delay added to the trailing edge of SBLK. This positions the rising edge of internal signal 1. DelayB[2:0] controls the delay added to the leading edge of 2. This positions the falling edge of internal signal 2. DelayB[5:3] controls the delay added to the trailing edge of SPIX. This positions the rising edge of internal signal 2. DelayB[8:6] is only used when SPIXopt=0. It controls the delay from the trailing edge of SBLK to the start of the internal 2 control. This delay is in addition to DelayA[5:3], the SBLK trailing edge delay. DelayA[8:6] controls the delay added to ADCLK. This is a simple delay. It adds the same delay to both the rising and falling edges of ADCLK to create 4.
XRD98L61
tPIX Black Sample Point CCD Signal tBK tVD Video Sample Point
DelayA[2:0] SBLK 1 DelayA[5:3]
SPIX 2 DelayA[5:3] + DelayB[8:6] DelayB[5:3]
ADCLK DelayA[8:6] 4 DelayA[8:6]
Figure 18. Effects of Aperture Delays with SPIXopt=0 (Default)
tPIX Black Sample Point CCD Signal tBK tVD DelayA[2:0] SBLK 1 DelayA[5:3] Video Sample Point
SPIX 2 DelayB[2:0] DelayB[5:3]
ADCLK DelayA[8:6] DelayA[8:6]
4
Figure 19. Effects of Aperture Delays with SPIXopt=1 Rev. 2.00
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XRD98L61
LINE RATE CLOCKS CLAMP & CAL are the two line rate clock signals. There are two modes of operation for these clocks. CAL & CLAMP Mode In this mode, the CLAMP signal is used to activate the DC restore Clamp at the CDS input, and the CAL signal is used to define the Optical Black pixels to be used for the Black Level calibration function. Typically the CLAMP pulse comes during the dummy or optical black pixels at the beginning of each scan line, and the CAL pulse comes during the longer string of optical black pixels at the end of each scan line. CLAMP & CAL must not be active at the same time. VS Reject Option (CAL & CLAMP Mode) In the CAL and CLAMP mode, there is an option to disconnect the CDS from the input pins during the Vertical Shift time. To enable this option, write a "1" to the VSreject bit in the Clock register. To properly define the Vertical Shift time, you must set the ClampCal bit properly. In the typical case, the CCD has a few OB pixels at the beginning of a line (CLAMP time) and a larger number of OB pixels at the end of a scan line (CAL time). In this case set the ClampCal bit = 0. This will define the Vertical shift time as the time from the end of the CAL pulse to the beginning of the CLAMP pulse. If a CCD has more OB pixels at the beginning of a line, then CAL should be active during these pixels and CLAMP should be active at the end of the line. In this case, set the ClampCal bit = 1. This will define the Vertical shift time as the time from the end of the CLAMP pulse to the beginning of the CAL pulse.
End of Line N
Start of Line N+1
Active Video Pixels
OB pixels
Vertical Shift
Dummy & OB pixels
Active Video pixels
CCD Signal CAL (Black Level) CLAMP (DC restore) Disconnect CDS from input pins Vert. Shift Reject (internal) tCAL
t CLAMP
Figure 20. Line Rate Timing with OneShot=0, VSreject=1 & ClampCal=0
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End of Line N
Start of Line N+1
Active Video Pixels
Dummy & OB pixels
Active Video pixels Vertical Shift OB pixels
CCD Signal CAL (Black Level) CLAMP (DC restore) Vert. Shift Reject (internal) tCLAMP Disconnect CDS from input pins t CAL
Figure 21. Line Rate Timing with OneShot=0, VSreject=1 & ClampCal=1
One Shot (CAL Only) Mode In this mode, the CAL signal is used to activate the DC restore clamp and to define the optical black pixels for calibration. The CAL pulse should frame the longest group of OB pixels at either the end or beginning of each line. The DC restore Clamp switch is turned ON during the first four pixels of each CAL pulse. The remaining pixels under the CAL pulse are used for black level calibration.
VS Reject Option (One Shot mode) The One Shot mode also has an option to disconnect the CDS from the input pins during the Vertical Shift time. To enable this option, write a "1" to the VSreject bit in the Clock register. The signal at the CLAMP pin is used to define the Vertical Shift period (i.e. the time when the CDS is disconnected from the input pins).
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End of Line N Start of Line N+1
Active Video Pixels
OB pixels
Vertical Shift
Dummy & OB pixels
Active Video pixels
CCD Signal Minimum 5 Pixels CAL 4 pixels t CAL
Internal DC restore time Internal Black Level calibration time
tCAL - 4 pixels
Disconnect CDS from input pins CLAMP (vertical shift)
Figure 22. Line Rate Timing with OneShot=1 & VSreject=1
SETTING POWER AND PERFORMANCE WITH Rext The power and performance levels of the XRD98L61 are set by the value of Rext. Rext sets the current bias level for the entire chip. Rext is connected between pin 39 (ExtRef) and analog ground (see Figure 23). This resistor should be placed as close as possible to the pin and routed directly to a ground plane in a PCB layout. A surface mount carbon resistor is recommended. Increasing values of Rext decrease the power, linearity and noise performance of the XRD98L61. Lowering the value of Rext increases linearity and noise performance while increasing power. The tested default value for Rext is 30KOhms. In order to match system to system performance and set consistent manufacturable performance levels between cameras, it is recommended that the Rext resistor have <1% tolerance. Rev. 2.00
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Digital-to-Analog Converters There are two voltage output, 8-bit resolution, Digitalto-Analog Converters (DACs) which can be used for a variety of purposes, and are controlled via the serial interface. On power up, these DACs are disabled. To activate them, you must write a "0" to the DAC0pd and DAC1pd bits in the Control register.
XRD98L61
15V
C1=0.1 F decoupling capacitors at each supply pin
CCD
0.01 F
0.01 F
Vdd
C1 C1
ASIC/DSP
25 Controls (These controls can be accessed via the serial interface as well) 24
36 AVDD DAC0 DAC1 AGND Test2 Test1 AVDD CCDin REFin AGND RESET PD
Rext
30K 0.1 F
37
Vdd
C1
ADCinP ADCinN ExtRef CapP CapN AGND AVDD OVER DB11 DB10 DB9 DB8 48
XRD98L61
OE SDI LOAD SCLK AGND AVDD DGND
Serial Interface C1
Vdd
C1
DB7 DB6 DB5 OGND OVDD DB4 DB3 DB2 DB1 DB0 Test3 CAL
DVDD ADCLK SPIX SBLK CLAMP 13
Vdd
Timing Generator
1 C1
12
DVdd
Vdd
12+1
Digital Video Input
Figure 23. Typical Application Schematic
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XRD98L61
300
AVDD = DVDD = 2.7V FS = 20MHz
250
-20 DEG C 25 DEG C 75 DEG C
POWER DISSIPATION (mW)
150
200
.
0 10
50
100
15
20
25
30
35
40
45
50
R
EXT
(k-ohm)
Figure 24. XRD98L61 Power Dissipation vs REXT @ 20MHz
120 AVDD = DVDD = 2.7V FS = 20 MHz 100 -20 DEG C 25 DEG C 75 DEG C
SUPPLY CURRENT, mA
80
60
40
20
0 10 15 20 25 30 REXT KOhms , 35 40 45 50
Figure 25. XRD98L61 Supply Current vs REXT @ 20MHz
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75 REXT = 12.5K 70 REXT = 18.2K REXT = 25K REXT = 30K 65 REXT = 36K REXT = 45K SNR, dB 60 AVDD = DVDD = 2.7V FS = 20 MHz TA = 25 C SNR = SIGNAL peak-peak / RMS noise (shorted input)
55
50
45
40 0 6 12 18 PGA GAIN, dB 24 30 36
Figure 26. XRD98L61 SNR vs PGA Gain @ 20MHz with Different REXT
1.5 AVDD = DVDD = 2.7V FS = 20 MHz 1.0
0.5
+DNL @ -20 DEG C +DNL @ 25 DEG C +DNL @ 75 DEG C
DNL, LSB
0.0
-DNL @ -20 DEG C -DNL @ 25 DEG C -DNL @ 75 DEG C
-0.5
-1.0
-1.5
10 15 20 25 30 REXT, KOhms 35 40 45 50
Figure 25. XRD98L61 System DNL vs REXT @ 20MHz
Rev. 2.00
35
XRD98L61
0.25 0.2 0.15 0.1 0.05 DNL 0 -0.05 -0.1 -0.15 -0.2 -0.25 -0.3 -0.35 0 1000 2000 Code 3000 4000
Figure 26. Direct PGA Input DNL
Rev. 2.00
36
XRD98L61
48 LEAD THIN QUAD FLAT PACK
(7 x 7 x 1.4 mm TQFP)
REV. 2.00
D D1 36 25
37
24
D1
D
48
13
1 B A2 e
12
C A Seating Plane A1 L
SYMBOL A A1 A2 B C D D1 e L a
INCHES MIN MAX 0.055 0.063 0.002 0.053 0.007 0.004 0.346 0.272 0.006 0.057 0.011 0.008 0.362 0.28
MILLIMETERS MIN MAX 1.4 1.6 0.05 1.35 0.17 0.09 8.8 6.9 0.15 1.45 0.27 0.2 9.2 7.1
0.020 BSC 0.018 0.03 0 7
0.50 BSC 0.45 0.75 0 7
Note: The control dimension is the millimeter column
Rev. 2.00
37
XRD98L61
NOTICE EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infringement. Charts and schedules contained here in are only for illustration purposes and may vary depending upon a user's specific application. While the information in this publication has been carefully checked; no responsibility, however, is assumed for in accuracies. EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances. Copyright 2001 EXAR Corporation Datasheet May 2001 Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited. Rev. 2.00
38

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