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LTC1604 High Speed, 16-Bit, 333ksps Sampling A/D Converter with Shutdown
FEATURES
s s s s s s s
DESCRIPTION
The LTC(R)1604 is a 333ksps, 16-bit sampling A/D converter that draws only 220mW from 5V supplies. This high performance device includes a high dynamic range sample-and-hold, a precision reference and a high speed parallel output. Two digitally selectable power shutdown modes provide power savings for low power systems. The LTC1604's full-scale input range is 2.5V. Outstanding AC performance includes 90dB S/(N+D) and - 100dB THD at a sample rate of 333ksps. The unique differential input sample-and-hold can acquire single-ended or differential input signals up to its 15MHz bandwidth. The 68dB common mode rejection allows users to eliminate ground loops and common mode noise by measuring signals differentially from the source. The ADC has P compatible,16-bit parallel output port. There is no pipeline delay in conversion results. A separate convert start input and a data ready signal (BUSY) ease connections to FlFOs, DSPs and microprocessors.
, LTC and LT are registered trademarks of Linear Technology Corporation.
s s s s
A Complete, 333ksps 16-Bit ADC 90dB S/(N+D) and -100dB THD (Typ) Power Dissipation: 220mW (Typ) No Pipeline Delay No Missing Codes over Temperature Nap (7mW) and Sleep (10W) Shutdown Modes Operates with Internal 15ppm/C Reference or External Reference True Differential Inputs Reject Common Mode Noise 5MHz Full Power Bandwidth 2.5V Bipolar Input Range 36-Pin SSOP Package
APPLICATIONS
s s s s s s
Telecommunications Digital Signal Processing Multiplexed Data Acquisition Systems High Speed Data Acquisition Spectrum Analysis Imaging Systems
TYPICAL APPLICATION
2.2F 10F 10 36 5V 10F 5V 10F 3 VREF
+
35 AVDD
+
9
+
10 DGND SHDN 33 CS 32 RD 30 BUSY 27 OVDD 29 5V OR 3V 10F
AVDD
DVDD
4 REFCOMP
7.5k 1.75X
+
47F
4.375V
2.5V REF
AMPLITUDE (dB)
CONTROL LOGIC AND TIMING
CONVST 31
P CONTROL LINES
1 AIN+ DIFFERENTIAL ANALOG INPUT 2.5V 2 AIN-
+ -
OGND 28 16-BIT SAMPLING ADC AGND 5 AGND 6 B15 TO B0 OUTPUT BUFFERS 16-BIT PARALLEL BUS 11 TO 26
D15 TO D0
AGND 7
AGND VSS 8 34
1604 TA01
+
-5V
10F
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+
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LTC1604 4096 Point FFT
0 -20 -40 -60 -80 -100 -120 -140 0 fSAMPLE = 333kHz fIN = 100kHz SINAD = 89dB THD = -96dB
20
40
60 80 100 120 140 160 FREQUENCY (kHz)
1604 TA02
1
LTC1604
ABSOLUTE MAXIMUM RATINGS
AVDD = DVDD = OVDD = VDD (Notes 1, 2)
PACKAGE/ORDER INFORMATION
TOP VIEW AIN+ AIN- VREF REFCOMP AGND AGND AGND AGND DVDD 1 2 3 4 5 6 7 8 9 36 AVDD 35 AVDD 34 VSS 33 SHDN 32 CS 31 CONV 30 RD 29 OVDD 28 OGND 27 BUSY 26 D0 25 D1 24 D2 23 D3 22 D4 21 D5 20 D6 19 D7 G PACKAGE 36-LEAD PLASTIC SSOP
Supply Voltage (VDD) ................................................ 6V Negative Supply Voltage (VSS)................................ - 6V Total Supply Voltage (VDD to VSS) .......................... 12V Analog Input Voltage (Note 3) ......................... (VSS - 0.3V) to (VDD + 0.3V) VREF Voltage (Note 4) ................. - 0.3V to (VDD + 0.3V) REFCOMP Voltage (Note 4) ......... - 0.3V to (VDD + 0.3V) Digital Input Voltage (Note 4) ....................- 0.3V to 10V Digital Output Voltage .................. - 0.3V to (VDD + 0.3V) Power Dissipation ............................................. 500mW Operating Temperature Range LTC1604C............................................... 0C to 70C LTC1604I ............................................ - 40C to 85C Storage Temperature Range ................ - 65C to 150C Lead Temperature (Soldering, 10 sec)................. 300C
ORDER PART NUMBER LTC1604CG LTC1604IG LTC1604ACG LTC1604AIG
DGND 10 D15 (MSB) 11 D14 12 D13 13 D12 14 D11 15 D10 16 D9 17 D8 18
TJMAX = 125C, JA = 95C/W
Consult factory for Military grade parts.
CO VERTER CHARACTERISTICS
PARAMETER Resolution (No Missing Codes) Integral Linearity Error Transition Noise Offset Error Offset Tempco Full-Scale Error Full-Scale Tempco (Note 7) (Note 8) (Note 9) (Note 9) Internal Reference External Reference CONDITIONS
With Internal Reference (Notes 5, 6)
MIN
q q
LTC1604 TYP MAX 16 1 0.7 4
MIN 16
LTC1604A TYP MAX 16 0.5 0.7 0.05 0.125 0.5 0.125 0.25 0.25 15 2
UNITS Bits LSB LSB % ppm/C % % ppm/C
15
q
0.05 0.125 0.5 0.125 0.25 0.25 15
IOUT(Reference) = 0, Internal Reference
A ALOG I PUT
SYMBOL PARAMETER VIN IIN CIN tACQ tAP tjitter CMRR Analog Input Range (Note 2) Analog Input Leakage Current Analog Input Capacitance Sample-and-Hold Acquisition Time Sample-and-Hold Acquisition Delay Time Sample-and-Hold Acquisition Delay Time Jitter Analog Input Common Mode Rejection Ratio - 2.5V < (AIN = AIN
- +) < 2.5V
CONDITIONS 4.75 VDD 5.25V, - 5.25 VSS - 4.75V, VSS (AIN-, AIN+) AVDD CS = High Between Conversions During Conversions
q
MIN
TYP 2.5
MAX
UNITS V
1 43 5 380 - 1.5 5 68
psRMS dB
2
U
W
U
U
WW
W
U
U
U
A pF pF ns ns
LTC1604
DY A IC ACCURACY
SYMBOL PARAMETER S/N Signal-to-Noise Ratio
S/(N + D) Signal-to-(Noise + Distortion) Ratio THD SFDR IMD Total Harmonic Distortion Up to 5th Harmonic Spurious Free Dynamic Range Intermodulation Distortion Full Power Bandwidth Full Linear Bandwidth (S/(N + D) 84dB
I TER AL REFERE CE CHARACTERISTICS
PARAMETER VREF Output Voltage VREF Output Tempco VREF Line Regulation VREF Output Resistance REFCOMP Output Voltage CONDITIONS IOUT = 0 IOUT = 0 4.75 VDD 5.25V - 5.25V VSS - 4.75V 0 IOUT 1mA IOUT = 0
DIGITAL I PUTS A D DIGITAL OUTPUTS
SYMBOL VIH VIL IIN CIN VOH VOL IOZ COZ ISOURCE ISINK PARAMETER High Level Input Voltage Low Level Input Voltage Digital Input Current Digital Input Capacitance High Level Output Voltage Low Level Output Voltage Hi-Z Output Leakage D15 to D0 Hi-Z Output Capacitance D15 to D0 Output Source Current Output Sink Current CONDITIONS VDD = 5.25V VDD = 4.75V VIN = 0V to VDD
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WU U
(Note 5)
LTC1604 TYP MAX 90 90 90 89 -100 - 94 96 - 88 5 350 LTC1604A MIN TYP MAX 87 90 90 90 89 - 100 - 94 - 88 96 - 88 5 350
CONDITIONS 5kHz Input Signal 100kHz Input Signal 5kHz Input Signal 100kHz Input Signal (Note 10) 5kHz Input Signal 100kHz Input Signal 100kHz Input Signal fIN1 = 29.37kHz, fIN2 = 32.446kHz
q
MIN
UNITS dB dB dB dB dB dB dB dB MHz kHz
q q
84
U
(Note 5)
MIN 2.475 TYP 2.500 15 0.01 0.01 7.5 4.375 MAX 2.515 UNITS V ppm/C LSB/V LSB/V k V
(Note 5)
MIN
q q q
TYP
MAX 0.8 1 0
UNITS V V A pF V V
2.4
5 VDD = 4.75V, IOUT = - 10A VDD = 4.75V, IOUT = - 400A VDD = 4.75V, IOUT = 160A VDD = 4.75V, IOUT = 1.6mA VOUT = 0V to VDD, CS High CS High (Note 11) VOUT = 0V VOUT = VDD 4.5
q q q q
4.0 0.05 0.10 0.4 10 15 -10 10
V V A pF mA mA
3
LTC1604
POWER REQUIRE E TS
SYMBOL VDD VSS IDD PARAMETER Positive Supply Voltage Negative Supply Voltage Positive Supply Current Nap Mode Sleep Mode Negative Supply Current Nap Mode Sleep Mode Power Dissipation Nap Mode Sleep Mode
ISS
PD
TI I G CHARACTERISTICS
SYMBOL fSMPL(MAX) tCONV tACQ tACQ+CONV t1 t2 t3 t4 t5 t6 t7 t8 t9 t10 PARAMETER Maximum Sampling Frequency Conversion Time Acquisition Time
Throughput Time (Acquisition + Conversion) CS to RD Setup Time CS to CONVST Setup Time SHDN to CS Setup Time SHDN to CONVST Wake-Up Time CONVST Low Time CONVST to BUSY Delay Data Ready Before BUSY (Notes 11, 12) (Notes 11, 12) (Notes 11, 12) CS = Low (Note 12) (Note 12) CL = 25pF
Delay Between Conversions Wait Time RD After BUSY Data Access Time After RD
t11
Bus Relinquish Time LTC1604C LTC1604I
q q q q
t12 t13 t14
RD Low Time CONVST High Time Aperture Delay of Sample-and-Hold
4
UW
(Note 5)
CONDITIONS (Notes 12, 13) (Note 12) CS = RD = 0V CS = 0V, SHDN = 0V CS = 5V, SHDN = 0V CS = RD = 0V CS = 0V, SHDN = 0V CS = 5V, SHDN = 0V CS = RD = 0V CS = 0V, SHDN = 0V CS = 5V, SHDN = 0V
q
MIN 4.75 - 4.75
TYP
MAX 5.25 - 5.25
UNITS V V mA mA A mA A A mW mW mW
18 1.5 1 26 1 1 220 7.5 0.01
30 2.4 100 40 100 100 350 12 1
q
q
UW
(Note 5)
CONDITIONS
q q
MIN 333 1.5
TYP 2.45
MAX 2.8 480 3
UNITS kHz s ns s ns ns ns
(Note 11)
q q q q q
0 10 10 400 40 36 80 60 32 200 -5 40 50 60 60 75 60 70 75
ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns
q q q
(Note 12) (Note 12) CL = 25pF
q q q
CL = 100pF
q
45 50
(Note 12) (Note 12)
t10 40 2
ns
LTC1604 TI I G CHARACTERISTICS
The q denotes specifications that apply over the full operating temperature range. Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: All voltage values are with respect to ground with DGND, OGND and AGND wired together unless otherwise noted. Note 3: When these pin voltages are taken below VSS or above VDD, they will be clamped by internal diodes. This product can handle input currents greater than 100mA below VSS or above VDD without latchup. Note 4: When these pin voltages are taken below VSS, they will be clamped by internal diodes. This product can handle input currents greater than 100mA below VSS without latchup. These pins are not clamped to VDD. Note 5: VDD = 5V, VSS = - 5V, fSMPL = 333kHz, and t r = t f = 5ns unless otherwise specified. Note 6: Linearity, offset and full-scale specification apply for a singleended AIN+ input with AIN- grounded.
TYPICAL PERFORMANCE CHARACTERISTICS
Integral Nonlinearity vs Output Code
2.0 1.5 1.0
1.0 0.8 0.6 0.4
SINAD (dB)
INL (LSB)
DNL (LSB)
0.5 0.0 -0.5 -1.0 -1.5 -2.0 -32768
-16384
0 CODE
16384
Signal-to-Noise Ratio vs Input Frequency
AMPLITUDE (dB BELOW THE FUNDAMENTAL)
100 90
SIGNAL-TO-NOISE RATIO (dB)
SPURIOUS-FREE DYNAMIC RANGE (dB)
80 70 60 50 40 30 20 10 0 1k 10k 100k FREQUENCY (Hz) 1M
1604 G03
UW
UW
(Note 5)
Note 7: Integral nonlinearity is defined as the deviation of a code from a straight line passing through the actual endpoints of the transfer curve. The deviation is measured from the center of the quantization band. Note 8: Typical RMS noise at the code transitions. See Figure 17 for histogram. Note 9: Bipolar offset is the offset voltage measured from - 0.5LSB when the output code flickers between 0000 0000 0000 0000 and 1111 1111 1111 1111. Note 10: Signal-to-Noise Ratio (SNR) is measured at 5kHz and distortion is measured at 100kHz. These results are used to calculate Signal-to-Nosie Plus Distortion (SINAD). Note 11: Guaranteed by design, not subject to test. Note 12: Recommended operating conditions. Note 13: The falling CONVST edge starts a conversion. If CONVST returns high at a critical point during the conversion it can create small errors. For best performance ensure that CONVST returns high either within 250ns after conversion start or after BUSY rises.
Differential Nonlinearity vs Output Code
100 90 80 70 60 50 40 30 20 10 0
-16384 0 CODE
1604 G10
S/(N + D) vs Input Frequency and Amplitude
VIN = 0dB VIN = -20dB
0.2 0.0 -0.2 -0.4 -0.6 -0.8 -1.0
VIN = -40dB
32767
1604 G11
-32768
16384
32767
1k
10k 100k FREQUENCY (Hz)
1M
1604 G01
Distortion vs Input Frequency
0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 -110 1k 100k INPUT FREQUENCY (Hz) 10k THD 3RD 2ND 1M
1604 G04
Spurious-Free Dynamic Range vs Input Frequency
0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 -110 1k 10k 100k INPUT FREQUENCY (Hz) 1M
1604 G05
5
LTC1604 TYPICAL PERFORMANCE CHARACTERISTICS
Intermodulaton Distortion
0
AMPLITUDE OF POWER SUPPLY FEEDTHROUGH (dB)
-20 -40 -60 -80
COMMON MODE REJECTION (dB) 1M
1604 G07
-20 -40
AMPLITUDE (dB)
fSAMPLE = 333kHz fIN1 = 29.3kHz fIN2 = 32.4kHz
-60 -80
-100 -120 -140 0 20 40 60 80 100 120 140 160 FREQUENCY (kHz)
1604 G06
PIN FUNCTIONS
AIN+ (Pin 1): Positive Analog Input. The ADC converts the difference voltage between AIN+ and AIN- with a differential range of 2.5V. AIN+ has a 2.5V input range when AIN- is grounded. AIN- (Pin 2): Negative Analog Input. Can be grounded, tied to a DC voltage or driven differentially with AIN+ . VREF (Pin 3): 2.5V Reference Output. Bypass to AGND with 2.2F tantalum in parallel with 0.1F ceramic. REFCOMP (Pin 4): 4.375 Reference Compensation Pin. Bypass to AGND with 47F tantalum in parallel with 0.1F ceramic. AGND (Pins 5 to 8): Analog Grounds. Tie to analog ground plane. DVDD (Pin 9): 5V Digital Power Supply. Bypass to DGND with 10F tantalum in parallel with 0.1F ceramic. DGND (Pin 10): Digital Ground for Internal Logic. Tie to analog ground plane. D15 to D0 (Pins 11 to 26): Three-State Data Outputs. D15 is the Most Significant Bit. BUSY (Pin 27): The BUSY output shows the converter status. It is low when a conversion is in progress. Data is valid on the rising edge of BUSY. OGND (Pin 28): Digital Ground for Output Drivers. OVDD (Pin 29): Digital Power Supply for Output Drivers. Bypass to OGND with 10F tantalum in parallel with 0.1F ceramic. RD (Pin 30): Read Input. A logic low enables the output drivers when CS is low. CONVST (Pin 31): Conversion Start Signal. This active low signal starts a conversion on its falling edge when CS is low. CS (Pin 32): The Chip Select Input. Must be low for the ADC to recognize CONVST and RD inputs. SHDN (Pin 33): Power Shutdown. Drive this pin low with CS low for nap mode. Drive this pin low with CS high for sleep mode. VSS (Pin 34): - 5V Negative Supply. Bypass to AGND with 10F tantalum in parallel with 0.1F ceramic. AVDD (Pin 35): 5V Analog Power Supply. Bypass to AGND with 10F tantalum in parallel with 0.1F ceramic. AVDD (Pin 36): 5V Analog Power Supply. Bypass to AGND with 10F tantalum in parallel with 0.1F ceramic and connect this pin to Pin 35 with a 10 resistor.
6
UW
Power Supply Feedthrough vs Ripple Frequency
0 fSAMPLE = 333kHz VRIPPLE = 10mV 80 70 60 50 40 30 20 10 0 1k 10k 100k INPUT FREQUENCY (Hz)
Input Common Mode Rejection vs Input Frequency
AVDD V SS
-100 -120
1k
10k 100k INPUT FREQUENCY (Hz)
1M
1604G09
U
U
U
LTC1604
FU CTIO AL BLOCK DIAGRA
2.2F 10F
3 VREF
+
36
AVDD
4 REFCOMP
+
47F
4.375V
1.75X
1 AIN+ DIFFERENTIAL ANALOG INPUT 2.5V 2 AIN-
+ -
OGND 28 16-BIT SAMPLING ADC AGND 5 AGND 6 B15 TO B0 OUTPUT BUFFERS 16-BIT PARALLEL BUS 11 TO 26
D15 TO D0
AGND 7
AGND VSS 8 34
+
-5V
10F
TEST CIRCUITS
Load Circuits for Access Timing Load Circuits for Output Float Delay
5V 1k DN 1k CL DN CL DN 1k CL DN
(A) Hi-Z TO VOH AND VOL TO VOH
(B) Hi-Z TO VOL AND VOH TO VOL
1604 TC01
(A) VOH TO Hi-Z
+
W
10 5V 10F 5V 10F 35 AVDD
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U
+
9
+
10 DGND SHDN 33 CS 32 CONVST 31 RD 30 BUSY 27 OVDD 29 5V OR 3V 10F P CONTROL LINES
DVDD
7.5k
2.5V REF
CONTROL LOGIC AND TIMING
1604 TA01
5V 1k
CL
(B) VOL TO Hi-Z
1604 TC02
7
LTC1604
APPLICATIONS INFORMATION
CONVERSION DETAILS The LTC1604 uses a successive approximation algorithm and internal sample-and-hold circuit to convert an analog signal to a 16-bit parallel output. The ADC is complete with a sample-and-hold, a precision reference and an internal clock. The control logic provides easy interface to microprocessors and DSPs. (Please refer to the Digital Interface section for the data format.) Conversion start is controlled by the CS and CONVST inputs. At the start of the conversion the successive approximation register (SAR) resets. Once a conversion cycle has begun it cannot be restarted. During the conversion, the internal differential 16-bit capacitive DAC output is sequenced by the SAR from the Most Significant Bit (MSB) to the Least Significant Bit (LSB). Referring to Figure 1, the AIN+ and AIN- inputs are acquired during the acquire phase and the comparator offset is nulled by the zeroing switches. In this acquire phase, a duration of 480ns will provide enough time for the sample-and-hold capacitors to acquire the analog signal. During the convert phase the comparator zeroing switches open, putting the comparator into compare mode. The input switches connect the CSMPL capacitors to ground, transferring the differential analog input charge onto the
CSMPL AIN+ SAMPLE HOLD CSMPL AIN- SAMPLE HOLD HOLD +CDAC ZEROING SWITCHES HOLD
+
-CDAC +VDAC COMP
-
-VDAC SAR
16
OUTPUT LATCHES
Figure 1. Simplified Block Diagram
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summing junctions. This input charge is successively compared with the binary-weighted charges supplied by the differential capacitive DAC. Bit decisions are made by the high speed comparator. At the end of a conversion, the differential DAC output balances the AIN+ and AIN- input charges. The SAR contents (a 16-bit data word) which represent the difference of AIN+ and AIN- are loaded into the 16-bit output latches. DIGITAL INTERFACE The A/D converter is designed to interface with microprocessors as a memory mapped device. The CS and RD control inputs are common to all peripheral memory interfacing. A separate CONVST is used to initiate a conversion. Internal Clock The A/D converter has an internal clock that runs the A/D conversion. The internal clock is factory trimmed to achieve a typical conversion time of 2.45s and a maximum conversion time of 2.8s over the full temperature range. No external adjustments are required. The guaranteed maximum acquisition time is 480ns. In addition, a throughput time (acquisition + conversion) of 3s and a minimum sampling rate of 333ksps are guaranteed. 3V Input/Output Compatible The LTC1604 operates on 5V supplies, which makes the device easy to interface to 5V digital systems. This device can also talk to 3V digital systems: the digital input pins (SHDN, CS, CONVST and RD) of the LTC1604 recognize 3V or 5V inputs. The LTC1604 has a dedicated output supply pin (OVDD) that controls the output swings of the digital output pins (D0 to D15, BUSY) and allows the part to talk to either 3V or 5V digital systems. The output is two's complement binary. Power Shutdown
* * *
D15 D0
1604 F01
The LTC1604 provides two power shutdown modes, Nap and Sleep, to save power during inactive periods. The Nap mode reduces the power by 95% and leaves only the digital logic and reference powered up. The wake-up time from Nap to active is 200ns. In Sleep mode all bias
LTC1604
APPLICATIONS INFORMATION
SHDN t3 CS
1604 F02a
Figure 2a. Nap Mode to Sleep Mode Timing
SHDN t4 CONVST
1604 F02b
Figure 2b. SHDN to CONVST Wake-Up Timing
CS t2 CONVST t1 RD
1604 F03
Figure 3. CS top CONVST Setup Timing
4
CHANGE IN DNL (LSB)
3
2 tCONV tACQ
1
0
0
400
800
1200
1600
2000
2400
CONVST LOW TIME, t5 (ns)
1604 F04
Figure 4. Change in DNL vs CONVST Low Time. Be Sure the CONVST Pulse Returns High Early in the Conversion or After the End of Conversion
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currents are shut down and only leakage current remains (about 1A). Wake-up time from Sleep mode is much slower since the reference circuit must power up and settle. Sleep mode wake-up time is dependent on the value of the capacitor connected to the REFCOMP (Pin 4). The wake-up time is 160ms with the recommended 47F capacitor. Shutdown is controlled by Pin 33 (SHDN). The ADC is in shutdown when SHDN is low. The shutdown mode is selected with Pin 32 (CS). When SHDN is low, CS low selects nap and CS high selects sleep. Timing and Control Conversion start and data read operations are controlled by three digital inputs: CONVST, CS and RD. A falling edge applied to the CONVST pin will start a conversion after the ADC has been selected (i.e., CS is low). Once initiated, it cannot be restarted until the conversion is complete. Converter status is indicated by the BUSY output. BUSY is low during a conversion. We recommend using a narrow logic low or narrow logic high CONVST pulse to start a conversion as shown in Figures 5 and 6. A narrow low or high CONVST pulse prevents the rising edge of the CONVST pulse from upsetting the critical bit decisions during the conversion time. Figure 4 shows the change of the differential nonlinearity error versus the low time of the CONVST pulse. As shown, if CONVST returns high early in the conversion (e.g., CONVST low time <500ns), accuracy is unaffected. Similarly, if CONVST returns high after the conversion is over (e.g., CONVST low time >tCONV), accuracy is unaffected. For best results, keep t 5 less than 500ns or greater than tCONV. Figures 5 through 9 show several different modes of operation. In modes 1a and 1b (Figures 5 and 6), CS and RD are both tied low. The falling edge of CONVST starts the conversion. The data outputs are always enabled and data can be latched with the BUSY rising edge. Mode 1a shows operation with a narrow logic low CONVST pulse. Mode 1b shows a narrow logic high CONVST pulse. In mode 2 (Figure 7) CS is tied low. The falling edge of CONVST signal starts the conversion. Data outputs are in
2800
9
LTC1604
APPLICATIONS INFORMATION
CS = RD = 0 t5 CONVST t6 BUSY t7 DATA DATA (N - 1) D15 TO D0 DATA N D15 TO D0 DATA (N + 1) D15 TO D0
1604 F05
t CONV
Figure 5. Mode 1a. CONVST Starts a Conversion. Data Outputs Always Enabled (CONVST = )
CS = RD = 0 t13 CONVST t6 BUSY
tCONV t5
DATA
DATA (N - 1) D15 TO D0
Figure 6. Mode 1b. CONVST Starts a Conversion. Data Outputs Always Enabled (CONVST = )
CS = 0
tCONV t5
CONVST t6 BUSY t9 t 12 RD t 10 DATA DATA N D15 TO D0
1604 F07
Figure 7. Mode 2. CONVST Starts a Conversion. Data is Read by RD
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t8
t8
t6
t7 DATA N D15 TO D0 DATA (N + 1) D15 TO D0
1604 F06
t13 t8
t 11
LTC1604
APPLICATIONS INFORMATION
CS = 0 RD = CONVST t6 BUSY t 10 DATA DATA (N - 1) D5 TO D0 t7 DATA N D15 TO D0 DATA N D15 TO D0 DATA (N + 1) D15 TO D0
1604 F08
t CONV
Figure 8. Mode 2. Slow Memory Mode Timing
CS = 0 RD = CONVST t6 BUSY t 10 DATA
t CONV
t 11
DATA (N - 1) D15 TO D0
three-state until read by the MPU with the RD signal. Mode 2 can be used for operation with a shared data bus. In slow memory and ROM modes (Figures 8 and 9) CS is tied low and CONVST and RD are tied together. The MPU starts the conversion and reads the output with the combined CONVST-RD signal. Conversions are started by the MPU or DSP (no external sample clock is needed). In slow memory mode the processor applies a logic low to RD (= CONVST), starting the conversion. BUSY goes low, forcing the processor into a wait state. The previous conversion result appears on the data outputs. When the conversion is complete, the new conversion results appear on the data outputs; BUSY goes high, releasing the processor and the processor takes RD (= CONVST) back high and reads the new conversion data. In ROM mode, the processor takes RD (= CONVST) low, starting a conversion and reading the previous conversion result. After the conversion is complete, the processor can read the new result and initiate another conversion.
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t8
t 11
t8
DATA N D15 TO D0
1604 F09
Figure 9. ROM Mode Timing
DIFFERENTIAL ANALOG INPUTS Driving the Analog Inputs The differential analog inputs of the LTC1604 are easy to drive. The inputs may be driven differentially or as a singleended input (i.e., the AIN - input is grounded). The AIN+ and AIN - inputs are sampled at the same instant. Any unwanted signal that is common mode to both inputs will be reduced by the common mode rejection of the sampleand-hold circuit. The inputs draw only one small current spike while charging the sample-and-hold capacitors at the end of conversion. During conversion the analog inputs draw only a small leakage current. If the source impedance of the driving circuit is low, then the LTC1604 inputs can be driven directly. As source impedance increases so will acquisition time (see Figure 10). For minimum acquisition time with high source impedance, a buffer amplifier should be used. The only requirement is that the amplifier driving the analog input(s) must settle after the small current spike before the next conversion
11
LTC1604
APPLICATIONS INFORMATION
10
ACQUISITION TIME (s)
1
0.1
0.01 1 10 100 1k SOURCE RESISTANCE () 10k
1604 F10
Figure 10. tACQ vs Source Resistance
starts (settling time must be 200ns for full throughput rate). Choosing an Input Amplifier Choosing an input amplifier is easy if a few requirements are taken into consideration. First, to limit the magnitude of the voltage spike seen by the amplifier from charging the sampling capacitor, choose an amplifier that has a low output impedance (< 100) at the closed-loop bandwidth frequency. For example, if an amplifier is used in a gain of +1 and has a unity-gain bandwidth of 50MHz, then the output impedance at 50MHz should be less than 100. The second requirement is that the closed-loop bandwidth must be greater than 15MHz to ensure adequate small-signal settling for full throughput rate. If slower op amps are used, more settling time can be provided by increasing the time between conversions. The best choice for an op amp to drive the LTC1604 will depend on the application. Generally applications fall into two categories: AC applications where dynamic specifications are most critical and time domain applications where DC accuracy and settling time are most critical. The following list is a summary of the op amps that are suitable for driving the LTC1604. More detailed information is available in the Linear Technology databooks, the LinearViewTM CD-ROM and on our web site at: www.linear-tech. com.
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LT (R) 1007: Low Noise Precision Amplifier. 2.7mA supply current, 5V to 15V supplies, gain bandwidth product 8MHz, DC applications. LT1097: Low Cost, Low Power Precision Amplifier. 300A supply current, 5V to 15V supplies, gain bandwidth product 0.7MHz, DC applications. LT1227: 140MHz Video Current Feedback Amplifier. 10mA supply current, 5V to 15V supplies, low noise and low distortion. LT1360: 37MHz Voltage Feedback Amplifier. 3.8mA supply current, 5V to 15V supplies, good AC/DC specs. LT1363: 50MHz Voltage Feedback Amplifier. 6.3mA supply current, good AC/DC specs. LT1364/LT1365: Dual and Quad 50MHz Voltage Feedback Amplifiers. 6.3mA supply current per amplifier, good AC/ DC specs. Input Filtering The noise and the distortion of the input amplifier and other circuitry must be considered since they will add to the LTC1604 noise and distortion. The small-signal bandwidth of the sample-and-hold circuit is 15MHz. Any noise or distortion products that are present at the analog inputs will be summed over this entire bandwidth. Noisy input circuitry should be filtered prior to the analog inputs to minimize noise. A simple 1-pole RC filter is sufficient for many applications. For example, Figure 11 shows a 3000pF capacitor from AIN+ to ground and a 100 source resistor to limit the input bandwidth to 530kHz. The 3000pF capacitor also acts as a charge reservoir for the input sample-and-hold and isolates the ADC input from sampling glitch sensitive circuitry. High quality capacitors and resistors should be used since these components can add distortion. NPO and silver mica type dielectric capacitors have excellent linearity. Carbon surface mount resistors can also generate distortion from self heating and from damage that may occur during soldering. Metal film surface mount resistors are much less susceptible to both problems.
LinearView is a trademark of Linear Technology Corporation.
LTC1604
APPLICATIONS INFORMATION
ANALOG INPUT 100 3000pF 1 2 3 4 47F 5 AGND
1604 F11
AIN+
2.500V
AIN
-
LTC1604 VREF REFCOMP
47F R3 16k LTC1604 4.375V 4 REFCOMP REFERENCE AMP R2 12k
Figure 11. RC Input Filter Figure 12a. LTC1604 Reference Circuit
Input Range The 2.5V input range of the LTC1604 is optimized for low noise and low distortion. Most op amps also perform well over this same range, allowing direct coupling to the analog inputs and eliminating the need for special translation circuitry. Some applications may require other input ranges. The LTC1604 differential inputs and reference circuitry can accommodate other input ranges often with little or no additional circuitry. The following sections describe the reference and input circuitry and how they affect the input range. Internal Reference The LTC1604 has an on-chip, temperature compensated, curvature corrected, bandgap reference that is factory trimmed to 2.500V. It is connected internally to a reference amplifier and is available at VREF (Pin 3) (see Figure 12a). A 7.5k resistor is in series with the output so that it can be easily overdriven by an external reference or other circuitry (see Figure 12b). The reference amplifier gains the voltage at the VREF pin by 1.75 to create the required internal reference voltage. This provides buffering between the VREF pin and the high speed capacitive DAC. The reference amplifier compensation pin (REFCOMP, Pin 4) must be bypassed with a capacitor to ground. The reference amplifier is stable with capacitors of 22F or greater. For the best noise performance a 47F ceramic or 47F tantalum in parallel with a 0.1F ceramic is recommended.
5V VIN LT1019A-2.5 VOUT ANALOG INPUT 1 2 3 AIN+ AIN- VREF LTC1604 4
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3 VREF
R1 7.5k
BANDGAP REFERENCE
5 AGND
1604 F12a
+
10F 0.1F 5
REFCOMP
AGND
1604 F12b
Figure 12b. Using the LT1019-2.5 as an External Reference
The VREF pin can be driven with a DAC or other means shown in Figure 13. This is useful in applications where the peak input signal amplitude may vary. The input span of the ADC can then be adjusted to match the peak input signal, maximizing the signal-to-noise ratio. The filtering of the internal LTC1604 reference amplifier will limit the bandwidth and settling time of this circuit. A settling time of 20ms should be allowed for after a reference adjustment. Differential Inputs The LTC1604 has a unique differential sample-and-hold circuit that allows rail-to-rail inputs. The ADC will always convert the difference of AIN+ - AIN- independent of the common mode voltage (see Figure 15a). The common mode rejection holds up to extremely high frequencies (see Figure 14a). The only requirement is that both inputs
13
LTC1604
APPLICATIONS INFORMATION
1 ANALOG INPUT 2V TO 2.7V DIFFERENTIAL AIN+
-
2
AIN
LTC1604 LTC1450 2V TO 2.7V 3 VREF
4 47F 5
REFCOMP
AGND
1604 F13
Figure 13. Driving VREF with a DAC
80 COMMON MODE REJECTION (dB) 70 60 50 40 30 20 10 0 1k 10k 100k INPUT FREQUENCY (Hz) 1M
1604 G14a
Figure 14a. CMRR vs Input Frequency
can not exceed the AVDD or VSS power supply voltages. Integral nonlinearity errors (INL) and differential nonlinearity errors (DNL) are independent of the common mode voltage, however, the bipolar zero error (BZE) will vary. The change in BZE is typically less than 0.1% of the common mode voltage. Dynamic performance is also affected by the common mode voltage. THD will degrade as the inputs approach either power supply rail, from 96dB with a common mode of 0V to 86dB with a common mode of 2.5V or - 2.5V. Differential inputs allow greater flexibility for accepting different input ranges. Figure 14b shows a circuit that converts a 0V to 5V analog input signal with only an additional buffer that is not in the signal path.
OUTPUT CODE
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ANALOG INPUT
1 2
AIN+ AIN-
2.5V
0V TO 5V
+ -
3
VREF LTC1604
4 10F 5
REFCOMP AGND
1604 F14b
Figure 14b. Selectable 0V to 5V or 2.5V Input Range
Full-Scale and Offset Adjustment Figure 15a shows the ideal input/output characteristics for the LTC1604. The code transitions occur midway between successive integer LSB values (i.e., - FS + 0.5LSB, - FS + 1.5LSB, - FS + 2.5LSB,... FS - 1.5LSB, FS - 0.5LSB). The output is two's complement binary with 1LSB = FS - (- FS)/65536 = 5V/65536 = 76.3V. In applications where absolute accuracy is important, offset and full-scale errors can be adjusted to zero. Offset error must be adjusted before full-scale error. Figure 15b shows the extra components required for full-scale error adjustment. Zero offset is achieved by adjusting the offset applied to the AIN- input. For zero offset error apply
011...111 011...110
000...001 000...000 111...111 111...110 100...001 100...000 - (FS - 1LSB) FS - 1LSB
1604 F15a
INPUT VOLTAGE (AIN+ - AIN- )
Figure 15a. LTC1604 Transfer Characteristics
LTC1604
APPLICATIONS INFORMATION
-5V R8 50k R3 24k ANALOG INPUT 1 2 R4 100 R5 R7 47k 50k R6 24k 3 LTC1604 VREF AIN+ AIN-
4 5
+
47F
REFCOMP AGND
1604 F15b
0.1F
Figure 15b. Offset and Full-Scale Adjust Circuit
- 38V (i.e., - 0.5LSB) at AIN+ and adjust the offset at the AIN- input until the output code flickers between 0000 0000 0000 0000 and 1111 1111 1111 1111. For full-scale adjustment, an input voltage of 2.499886V (FS/2 - 1.5LSBs) is applied to AIN+ and R2 is adjusted until the output code flickers between 0111 1111 1111 1110 and 0111 1111 1111 1111. BOARD LAYOUT AND GROUNDING Wire wrap boards are not recommended for high resolution or high speed A/D converters. To obtain the best performance from the LTC1604, a printed circuit board with ground plane is required. Layout should ensure that digital and analog signal lines are separated as much as possible. Particular care should be taken not to run any digital track alongside an analog signal track or underneath the ADC.The analog input should be screened by AGND. An analog ground plane separate from the logic system ground should be established under and around the ADC. Pin 5 to Pin 8 (AGNDs), Pin 10 (ADC's DGND) and all other analog grounds should be connected to this single analog ground point. The REFCOMP bypass capacitor and the DVDD bypass capacitor should also be connected to this
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analog ground plane. No other digital grounds should be connected to this analog ground plane. Low impedance analog and digital power supply common returns are essential to low noise operation of the ADC and the foil width for these tracks should be as wide as possible. In applications where the ADC data outputs and control signals are connected to a continuously active microprocessor bus, it is possible to get errors in the conversion results. These errors are due to feedthrough from the microprocessor to the successive approximation comparator. The problem can be eliminated by forcing the microprocessor into a WAIT state during conversion or by using three-state buffers to isolate the ADC data bus. The traces connecting the pins and bypass capacitors must be kept short and should be made as wide as possible. The LTC1604 has differential inputs to minimize noise coupling. Common mode noise on the AIN+ and AIN- leads will be rejected by the input CMRR. The AIN- input can be used as a ground sense for the AIN+ input; the LTC1604 will hold and convert the difference voltage between AIN+ and AIN- . The leads to AIN+ (Pin 1) and AIN- (Pin 2) should be kept as short as possible. In applications where this is not possible, the AIN+ and AIN- traces should be run side by side to equalize coupling. SUPPLY BYPASSING High quality, low series resistance ceramic, 10F or 47F bypass capacitors should be used at the VDD and REFCOMP pins as shown in Figure 16 and in the Typical Application on the first page of this data sheet. Surface mount ceramic capacitors such as Murata GRM235Y5V106Z016 provide excellent bypassing in a small board space. Alternatively, 10F tantalum capacitors in parallel with 0.1F ceramic capacitors can be used. Bypass capacitors must be located as close to the pins as possible. The traces connecting the pins and the bypass capacitors must be kept short and should be made as wide as possible.
15
LTC1604
APPLICATIONS INFORMATION
1 AIN+ AIN- 2 LTC1604 VREF REFCOMP AGND 3 2.2F 4 47F 5 TO 8 VSS 34 10F AVDD 36 10F AVDD 35 10F DVDD 9 10F DGND OVDD OGND 10 29 10F 28 DIGITAL SYSTEM
ANALOG INPUT CIRCUITRY
+ -
Figure 16. Power Supply Grounding Practice
DC PERFORMANCE The noise of an ADC can be evaluated in two ways: signalto-noise raio (SNR) in frequency domain and histogram in time domain. The LTC1604 excels in both. Figure 18a demonstrates that the LTC1604 has an SNR of over 90dB in frequency domain. The noise in the time domain histogram is the transition noise associated with a high resolution ADC which can be measured with a fixed DC signal applied to the input of the ADC. The resulting output codes are collected over a large number of conversions. The shape of the distribution of codes will give an indication of the magnitude of the transition noise. In Figure 17 the distribution of output codes is shown for a DC input that has been digitized 4096 times. The distribution is Gaussian and the RMS code transition noise is about 0.66LSB. This corresponds to a noise level of 90.9dB relative to full scale. Adding to that the theoretical 98dB of quantization error for 16-bit ADC, the resultant corresponds to an SNR level of 90.1dB which correlates very well to the frequency domain measurements in DYNAMIC PERFORMANCE section. DYNAMIC PERFORMANCE The LTC1604 has excellent high speed sampling capability. Fast fourier transform (FFT) test techniques are used to test the ADC's frequency response, distortions and noise at the rated throughput. By applying a low distortion sine wave and analyzing the digital output using an FFT algorithm, the ADC's spectral content can be examined for frequencies outside the fundamental. Figures 18a and 18b show typical LTC1604 FFT plots.
COUNT
AMPLITUDE (dB)
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1604 F16
2500
2000
1500
1000
500
0 -5 -4 -3 -2 -1 0 1 CODE 2 3 4 5
1604 F17
Figure 17. Histogram for 4096 Conversions
0 -20 -40 -60 -80 -100 -120 -140 0 20 40 60 80 100 120 140 160 FREQUENCY (kHz)
1604 F18a
fSAMPLE = 333kHz fIN = 4.959kHz SINAD = 90.2dB THD = -103.2dB
Figure 18a. This FFT of the LTC1604's Conversion of a Full-Scale 5kHz Sine Wave Shows Outstanding Response with a Very Low Noise Floor When Sampling at 333ksps
LTC1604
APPLICATIONS INFORMATION
Signal-to-Noise Ratio The signal-to-noise plus distortion ratio [S/(N + D)] is the ratio between the RMS amplitude of the fundamental input frequency to the RMS amplitude of all other frequency components at the A/D output. The output is band limited to frequencies from above DC and below half the sampling frequency. Figure 18a shows a typical spectral content with a 333kHz sampling rate and a 5kHz input. The dynamic performance is excellent for input frequencies up to and beyond the Nyquist limit of 167kHz. Effective Number of Bits The effective number of bits (ENOBs) is a measurement of the resolution of an ADC and is directly related to the S/(N + D) by the equation: N = [S/(N + D) - 1.76]/6.02 where N is the effective number of bits of resolution and S/(N + D) is expressed in dB. At the maximum sampling rate of 333kHz the LTC1604 maintains above 14 bits up to the Nyquist input frequency of 167kHz (refer to Figure 19). Total Harmonic Distortion Total harmonic distortion (THD) is the ratio of the RMS sum of all harmonics of the input signal to the fundamental itself. The out-of-band harmonics alias into the frequency band between DC and half the sampling frequency. THD is expressed as:
V22 + V32 + V42 + ...Vn2 V1 where V1 is the RMS amplitude of the fundamental frequency and V2 through Vn are the amplitudes of the second through nth harmonics. THD vs Input Frequency is shown in Figure 20. The LTC1604 has good distortion performance up to the Nyquist frequency and beyond. THD = 20Log
EFFECTIVE BITS 0 -20 -40 -60 -80 -100 -120 -140 0 20 40 60 80 100 120 140 160
1604 F18b
AMPLITUDE (dB)
AMPLITUDE (dB BELOW THE FUNDAMENTAL)
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fSAMPLE = 333kHz fIN = 97.152kHz SINAD = 89dB THD = -96dB
FREQUENCY (kHz)
Figure 18b. Even with Inputs at 100kHz, the LTC1604's Dynamic Linearity Remains Robust
16 15 14 13 12 11 10 9 8 1k 10k 100k FREQUENCY (Hz) 98 92 86 80 74 68 62 56 50 1M
1604 F19
Figure 19. Effective Bits and Signal/(Noise + Distortion) vs Input Frequency
0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 -110 1k 100k INPUT FREQUENCY (Hz) 10k THD 3RD 2ND 1M
1604 G04
SINAD (dB)
Figure 20. Distortion vs Input Frequency
17
LTC1604
APPLICATIONS INFORMATION
Intermodulation Distortion If the ADC input signal consists of more than one spectral component, the ADC transfer function nonlinearity can produce intermodulation distortion (IMD) in addition to THD. IMD is the change in one sinusoidal input caused by the presence of another sinusoidal input at a different frequency. If two pure sine waves of frequencies fa and fb are applied to the ADC input, nonlinearities in the ADC transfer function can create distortion products at the sum and difference frequencies of mfa nfb, where m and n = 0, 1, 2, 3,
0 -20 -40 fSAMPLE = 333kHz fIN1 = 29.3kHz fIN2 = 32.4kHz
AMPLITUDE (dB)
-60 -80
-100 -120 -140 0 20 40 60 80 100 120 140 160 FREQUENCY (kHz)
1604 G06
Figure 21. Intermodulation Distortion Plot
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etc. For example, the 2nd order IMD terms include (fa - fb). If the two input sine waves are equal in magnitude, the value (in decibels) of the 2nd order IMD products can be expressed by the following formula:
IMD fa fb = 20Log
(
)
Amplitude at (fa fb) Amplitude at fa
Peak Harmonic or Spurious Noise The peak harmonic or spurious noise is the largest spectral component excluding the input signal and DC. This value is expressed in decibels relative to the RMS value of a full-scale input signal. Full-Power and Full-Linear Bandwidth The full-power bandwidth is that input frequency at which the amplitude of the reconstructed fundamental is reduced by 3dB for a full-scale input signal. The full-linear bandwidth is the input frequency at which the S/(N + D) has dropped to 84dB (13.66 effective bits). The LTC1604 has been designed to optimize input bandwidth, allowing the ADC to undersample input signals with frequencies above the converter's Nyquist Frequency. The noise floor stays very low at high frequencies; S/(N + D) becomes dominated by distortion at frequencies far beyond Nyquist.
LTC1604
PACKAGE DESCRIPTION
0.205 - 0.212** (5.20 - 5.38)
0.005 - 0.009 (0.13 - 0.22)
0.022 - 0.037 (0.55 - 0.95)
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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Dimensions in inches (millimeters) unless otherwise noted.
G Package 36-Lead Plastic SSOP (0.209)
(LTC DWG # 05-08-1640)
0.499 - 0.509* (12.67 - 12.93) 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19
0.301 - 0.311 (7.65 - 7.90)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 0.068 - 0.078 (1.73 - 1.99)
0 - 8
0.0256 (0.65) BSC
0.010 - 0.015 (0.25 - 0.38)
0.002 - 0.008 (0.05 - 0.21)
G36 SSOP 1196
19
LTC1604
TYPICAL APPLICATION
Using the LTC1604 and Two LTC1391s as an 8-Channel Differential 16-Bit ADC System
5V
LTC1391 CH0+ 1 2 3 4 5 6 7 CH7 + 8 CH0 CH1 CH2 CH3 CH4 CH5 CH6 CH7 V+ D 16 15
+
1F
14 V- DOUT DIN CS CLK GND 12 11 10 9
-5V 1F 4 REFCOMP 7.5k 1.75X CONTROL LOGIC AND TIMING
5V LTC1391 CH0 - 1 2 3 4 5 6 7 CH7
-
CH0 CH1 CH2 CH3 CH4 CH5 CH6 CH7
V+ D V- DOUT DIN CS CLK GND
16 15 14
12 11 10 9
8
RELATED PARTS
SAMPLING ADCs
PART NUMBER LTC1410 LTC1415 LTC1418 LTC1419 LTC1605 DESCRIPTION 12-Bit, 1.25Msps, 5V ADC 12-Bit, 1.25Msps, Single 5V ADC 14-Bit, 200ksps, Single 5V ADC Low Power 14-Bit, 800ksps ADC 16-Bit, 100ksps, Single 5V ADC COMMENTS 71.5dB SINAD at Nyquist, 150mW Dissipation 55mW Power Dissipation, 72dB SINAD 15mW, Serial/Para llel 10V True 14-Bit Linearity, 81.5dB SINAD, 150mW Dissipation 10V Inputs, 55mW, Byte or Parallel I/O
DACs
PART NUMBER LTC1595 LTC1596 LTC1597 LTC1650 DESCRIPTION 16-Bit Serial Multiplying IOUT DAC in SO-8 16-Bit Serial Multiplying IOUT DAC 16-Bit Parallel, Multiplying DAC 16-Bit Serial VOUT DAC COMMENTS 1LSB Max INL/DNL, Low Glitch, DAC8043 16-Bit Upgrade 1LSB Max INL/DNL, Low Glitch, AD7543/DAC8143 16-Bit Upgrade 1LSB Max INL/DNL, Low Glitch, 4 Quadrant Resistors Low Power, Low Gritch, 4-Quadrant Multiplication
20
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 q FAX: (408) 434-0507 q www.linear-tech.com
+
13
-5V DIN CS CLK P CONTROL LINES
+
+
13
1F
-5V
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2.2F
10F
10 36 AVDD
5V 10F
5V 10F
+
3 VREF
+
35 AVDD
+
9 DVDD 10 DGND SHDN 33 CS 32 CONVST 31 RD 30 BUSY 27 P CONTROL LINES
+
47F
4.375V
2.5V REF
LTC1604 1 AIN 3000pF 2 AIN- 3000pF AGND 5 AGND 6 AGND 7 AGND VSS 8 34 10F
+
OVDD 29
+
OGND 28 OUTPUT BUFFERS D15 TO D0 16-BIT PARALLEL BUS 11 TO 26
+ -
16-BIT SAMPLING ADC B15 TO B0
5V OR 3V 10F
1604 TA03
1604fa LT/TP 1098 REV A 2K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 1998

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