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19-0205; Rev 0; 7/94
N KI ATIO ALU LABLE EV I AVA
T
PDA/Hand-Held Computer Power Controller
_______________General Description
The MAX781 is a system-engineered power-supply controller for subnotebook computers, PDAs, or similar battery-powered equipment. It provides high-performance, step-down (buck), pulse-width modulated (PWM) control for generating +3.3V and constant-current battery charging. Dual PCMCIA VPP outputs are powered by a regulated flyback winding. Five high-side gate drivers and a buffered analog multiplexer are also included. All functions are controlled by an SPI/MicrowireTM compatible four-wire serial interface. The MAX781 generates +3.3V with high efficiency through synchronous rectification and PWM operation at heavy loads. It uses Idle ModeTM operation at light loads. Only small external components are required because of the device's high switching frequency (300kHz) and advanced current-mode PWM architecture that allows for output capacitance as low as 50F per ampere of load. The MAX781 is configured by 32 bits of serial data. These bits select the operating mode, set the switch-mode battery charger current level, select one of eight analog multiplexer channels, and turn on/off the five high-side gate drivers. A status byte read from the serial interface indicates if the battery has been removed, if the DC charging source has been connected, or if there is a fault condition on the +3.3V output. An interrupt output signals the CPU if a status signal changes.
____________________________Features
o +3.3V Step-Down Controller o Dual PCMCIA 2.0 Compatible VPP Outputs (0V/3.3V/5V/12V) o Digitally Adjustable Switching Current Source for Battery Charging o 5 High-Side Switch Gate-Driver Outputs o SPI Serial Interface o 300kHz Switching Frequency o Oscillator SYNC Input o 2.5V 1.5% Reference Output o 36-Pin SSOP Package
MAX781
________________________Applications
Subnotebook Computers PDAs Communicating Computers Handy-Terminals
______________Ordering Information
PART MAX781CBX MAX781EBX TEMP. RANGE 0C to +70C -40C to +85C PIN-PACKAGE 36 SSOP 36 SSOP
________________________________________________Typical Application Diagram
DCIN (up to 18V) HIGH-SIDE GATE DRIVERS 5 SUBSYSTEMS LOAD SWITCHES SELF REFRESH DRAM
MAX781
DIGITALLY ADJUSTABLE SWITCHING CURRENT SOURCE
+3.3V AT 1A OR MORE SERIAL INTERFACE 4 INTERRUPT VPPA
CPU
5 to 8 NiCd/NiMH CELLS or 2 LION CELLS
PCMCIA SLOT A PCMCIA SLOT B
VPPB
ANALOG MULTIPLEXER OUTPUT
ADC
Pin Configuration on last page.
TMSPI is a trademark of Motorola Inc. Microwire is a trademark of National Semiconductor Corp. Idle Mode is a trademark of Maxim Integrated Porducts. ________________________________________________________________ Maxim Integrated Products 1
Call toll free 1-800-998-8800 for free samples or literature.
PDA/Hand-Held Computer Power Controller MAX781
ABSOLUTE MAXIMUM RATINGS
BATT, VCHG, VHI to AGND.........................................-0.3V, 20V VPPA, VPPB to AGND..................................................-0.3V, 20V FAST, GD1, GD2, GD3, GD4, GD5 to AGND ..............-0.3V, 20V BST to AGND ...............................................................-0.3V, 30V BST to LX .......................................................................-0.3V, 7V DHI to LX .......................................................-0.3V, (BST + 0.3V) PGND to AGND ........................................................-0.3V, +0.3V All Other Pins to AGND or PGND ..................................-0.3V, 7V VPPA, VPPB Current .........................................................100mA 5OUT Current....................................................................100mA 3OUT Current......................................................................40mA Continuous Power Dissipation (TA = +70C) SSOP (derate 11.76mW/C above +70C) ....................941mW Operating Temperature Ranges MAX781CBX .........................................................0C to +70C MAX781EBX ......................................................-40C to +85C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10sec) .............................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(BATT = 6V, power-on reset state, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER SUPPLY AND REFERENCE --- - ---- Shutdown mode, SHDN = 0V --- - ---- Low-power mode, SHDN = BATT = 18V --- - ---- Standby mode, SHDN = BATT = 18V --- - ---- Operate mode, SHDN = BATT = 18V No load ISOURCE = -20A to 100A Operate or standby mode, 5.5V < BATT < 18V, 0mA < I5OUT < 25mA Low-power mode, 5.5V < BATT < 18V, 0mA < I5OUT < 10mA Internal Undervoltage Lockout Threshold (measured at 5OUT, UVLO = AGND) UVLO Threshold (measured at UVLO) UVLO Input Bias Current INTERNAL OSCILLATOR Internal Oscillator Frequency SYNC Capture Range (Note 1) SYNC Minimum Pulse Width (Note1) SYNC Fall Time (Note 1) SYNC Rise Time (Note 1) SYNC Input Voltage Low SYNC Input Voltage High SYNC Leakage Current 3.8 -100 100 SYNC = REF SYNC = AGND or 5OUT 270 170 270 500 200 1 0.75 300 230 340 260 350 kHz kHz ns ns s V V nA V5OUT rising V5OUT falling VUVLO rising VUVLO falling 2.463 -20 4.8 4.8 4.30 4.10 97 90 4.60 4.35 10 60 250 1 2.5 120 750 2 2.537 20 5.2 V 5.2 4.80 V 4.50 103 96 50 %REF nA mA V mV A CONDITIONS MIN TYP MAX UNITS
BATT Quiescent Supply Current
REF Output Voltage REF Load Regulation
5OUT Output Voltage
2
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PDA/Hand-Held Computer Power Controller
ELECTRICAL CHARACTERISTICS (continued)
(BATT = 6V, power-on reset state, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER 3.3V OUTPUT Low-power mode, 4V < BATT < 18V, 0mA < I3OUT < 1mA 3OUT Output Voltage Standby mode, 4V < BATT < 18V, 0mA < I3OUT < 10mA Operate mode, 4V < BATT < 18V, CS to 3OUT = 0mV to 80mV CS to 3OUT Current-Limit Threshold 3VINT Fault-Detect Threshold 3VINT Fault-Detect Hysteresis DLO On-Resistance DHI On-Resistance BATTINT Battery-Detect Threshold (measured at TEMP) VPP REGULATOR VHI Regulation Threshold Operate mode Operate mode, ISINK = 200A, VPPA1 = VPPA0 = 0, VPPB1 = VPPB0 = 0, GDSEL1 to GDSEL5 = 0 VHI = 20V Operate mode, VHI = 18V, VPPA1 = VPPA0 = 0, VPPB1 = VPPB0 = 0, GDSEL1 to GDSEL5 = 0 ISINK = 1mA, VPP_1 = 0, VPP_0 = 0 14.2V < VHI < 18V, VPP_1 = 0, VPP_0 = 1, 0mA < IVPP_ < 60mA VPP_Output Voltage 14.2V < VHI < 18V, VPP_1 = 1, VPP_0 = 0, 0mA < IVPP_ < 60mA 14.2V < VHI < 18V, VPP_1 = 1, VPP_0 = 1, 0mA < IVPP_ < 60mA HIGH-SIDE GATE DRIVERS GD_ Output High Voltage GD_ Output Low Voltage GD_ Source Current GD_ Sink Current VHI = 14.2V, GDSEL_ = 1, ISOURCE = 1A VHI = 14.2V, GDSEL_ = 0, ISINK = 20A GD_ = 2.5V, GDSEL_ = 1, VHI = 14.2V GD_ = 2.5V, GDSEL_ = 0, VHI = 14.2V 6 200 10 450 14 0.25 18 900 V V A A 11.4 3.14 12.0 3.3 12.6 3.49 4.75 5.0 1 12.8 13.5 14.2 V 3OUT falling High, 5OUT = 4.75V Low, 5OUT = 4.75V High or low, BST - LX = 4.5V TEMP falling TEMP rising 75 81 83 89 3.17 3.17 3.17 80 2.9 100 3.0 150 3.43 3.43 3.43 130 3.1 15 10 10 mV V mV %3OUT V CONDITIONS MIN TYP MAX UNITS
MAX781
VHI Clamp Voltage
20
V
VHI Clamp Current
mA
VHI Input Bias Current
45
A
0.25 5.25 V
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PDA/Hand-Held Computer Power Controller MAX781
ELECTRICAL CHARACTERISTICS (continued)
(BATT = 6V, power-on reset state, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER ANALOG MULTIPLEXER MUX2 = 0, MUX1 = 0, MUX0 = 0 MUX2 = 0, MUX1 = 0, MUX0 = 1 MUX2 = 0, MUX1 = 1, MUX0 = 0 AOUT Output Voltage MUX2 = 0, MUX1 = 1, MUX0 = 1 MUX2 = 1, MUX1 = 0, MUX0 = 0 MUX2 = 1, MUX1 = 0, MUX0 = 1 MUX2 = 1, MUX1 = 1, MUX0 = 0 MUX2 = 1, MUX1 = 1, MUX0 = 1 AOUT Output Low SERIAL INTERFACE CE, SCLK, DIN Logic Input High Voltage CE, SCLK, DIN Logic Input Low Voltage SCLK, DIN Leakage Current CE Internal Pull-Down Resistance DOUT, INT Logic Output High Voltage DOUT, INT Logic Output Low Voltage CE, SCLK, DIN Logic Input Rise/Fall Time (Note 1) BATTERY CHARGER DCHG On Resistance CSBAT Full-Scale Current-Sense Voltage COMP Current-Sense Amplifier Offset Voltage Current-Sense Amplifier CSBAT to COMP Transconductance (gm) FAST OUTPUT Output Sink Current FAST = 3V, FASTON = 1 FAST = 18V, FASTON = 0 1.0 2.0 1.0 mA nA High or low, 5OUT = 4.75V CHG6 to CHG0 = 1, CHARGE = 1 CSBAT = 0V 190 -2 400 200 0 600 10 210 2 750 mV mV mho ISOURCE = 1mA ISINK = 1.6mA -100 60 2.7 0.4 50 100 2 0.8 100 140 V V nA k V V ns ISINK = 10A 65.33 44.54 19.90 65.33 18.49 18.49 99.8 65.33 66.67 45.45 20.00 66.67 18.87 18.87 100 66.67 68.00 46.36 20.10 68.00 19.25 19.25 100.2 68.00 10 %3OUT %5OUT %BATT %TEMP %VPPA %VPPB %VREF %AUXIN mV CONDITIONS MIN TYP MAX UNITS
4
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PDA/Hand-Held Computer Power Controller
TIMING CHARACTERISTICS (Note 1)
PARAMETER DIN to SCLK Data Setup Time DIN to SCLK Data Hold Time SCLK to DOUT Valid Propagation Delay SCLK Clock Period SCLK High Pulse Width SCLK Low Pulse Width CE Assertion to DOUT Enable CE Deassertion to DOUT Disable CE Assertion to SCLK Rising-Edge Setup Time SCLK Rising Edge to CE Deassertion CE High Pulse Width SCLK Rising Edge to CE Assertion CE Deassertion to SCLK Rising Edge Note 1: Guaranteed by design. SYMBOL tDS tDH tDO tCP tCH tCL tDV tTR tCSS tCSH tCSW tCS0 tCS1 200 200 300 200 200 MIN 125 0 30 400 125 125 120 120 200 TYP MAX UNITS ns ns ns ns ns ns ns ns ns ns ns ns ns
MAX781
__________________________________________Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
NO LOAD SUPPLY CURRENT
OPERATE MODE (IDLE = 0) QUIESCENT CURRENT (mA) 1 OPERATE MODE (IDLE = 1) STANDBY MODE 0.1
(I3OUT=0mA) SYNC=UVLO=AGND, CHARGE=0 GDSEL_=0 MUX_=0 SHUTDOWN MODE 5ON=1 VPP_=0
MAX781-01
CHARGER OUTPUT CURRENT
% CURRENT INTO BATT (mA)
MAX781-03
10
1000
100 90 80 70 60 EFFICIENCY (%)
LOW-POWER MODE
100 mA R4 = 0.2 SYNC = AGND BATT = 7V TO 8V VCHG = 12V 1 3 7 15 31 63 127
50 40 30 20 10
0.01
0.001 2 4 6 8 10 12 14 16 18 BATT INPUT VOLTAGE (V)
10
CHARGER CODE (CHG6-CHG0 VALUE)
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PDA/Hand-Held Computer Power Controller MAX781
____________________________Typical Operating Characteristics (continued)
(TA = +25C, unless otherwise noted.)
VPPA AND VPPB OUTPUT POWER VPPA SHORTED TO VPPB AND CLAMPED TO 11.5V
MAX781-02
DCHG DUTY CYCLE vs. COMP VOLTAGE
MAX781-04
3OUT OPERATE MODE POWER EFFICIENCY (FIXED 300kHz SWITCHING FREQUENCY)
90 POWER EFFICIENCY (%) 80 70 60 50 40 30 20 10 BATT = 5.5V SYNC = REF IDLE = 0 MODE1 = 1 MODE0 = 0
MAX781-05
400 VHI VOLTAGE 350 CURRENT (mA) 300 250 200 150 100 50 4 6
CONFIGURATION = $FF, $00, $02, $6A, SYNC = AGND, NO 3OUT LOAD T1 TURNS RATIO (SECONDARY TURNS / PRIMARY TURNS) = 3.5
14.0 13.5 VHI VOLTAGE (V) 13.0 12.5 DCHG DUTY CYCLE (%)
90 80 70 60 50 40 30 20 AT 0% DUTY CYCLE, DCHG = 5OUT
100
BATT INPUT CURRENT
VPPA + VPPB CURRENT
12.0 11.5 11.0 10.5
10 0 0 0.5 1.0 1.5 2.0 2.5 3.0 COMP VOLTAGE (V)
8
10
12
14
16
18
1
10
100
1000
BATT VOLTAGE (V)
3OUT OUTPUT CURRENT (mA)
3OUT OPERATE MODE POWER EFFICIENCY (FIXED 230kHz SWITCHING FREQUENCY)
MAX781-06
3OUT OPERATE MODE POWER EFFICIENCY (VARIABLE SWITCHING FREQUENCY)
MAX781-12
3OUT OPERATE MODE POWER EFFICIENCY (VARIABLE SWITCHING FREQUENCY)
400 350 300 250 200 90 SWITCHING FREQUENCY (kHz) POWER EFFICIENCY (%) 80 70 60 50 40 30 20 10 1 10 100 3OUT OUTPUT CURRENT (mA) % kHz 150 100 50 0 1000 BATT = 5.5V SYNC = AGND IDLE = 1 MODE1 = 1 MODE0 = 0
MAX781-10
100 90 POWER EFFICIENCY (%) 80 70 60 50 40 30 20 10 1 10 100 BATT = 5.5V SYNC = AGND IDLE = 0 MODE1 = 1 MODE0 = 0
100 90 POWER EFFICIENCY (%) 80 70 60 50
350 300 250 200
% kHz
40 30 20 10
150 100 50 1 10 100 0 1000
1000
3OUT OUTPUT CURRENT (mA)
3OUT OUTPUT CURRENT (mA)
3OUT OPERATE MODE POWER EFFICIENCY (FIXED 300kHz SWITCHING FREQUENCY)
MAX781-08
3OUT OPERATE MODE POWER EFFICIENCY (FIXED 230kHz SWITCHING FREQUENCY)
MAX781-07
3OUT OPERATE MODE POWER EFFICIENCY (VARIABLE SWITCHING FREQUENCY)
90 POWER EFFICIENCY (%) 80 70 60 50 40 30 20 10 % kHz 150 100 50 1 10 100 0 1000 BATT = 7.5V SYNC = REF IDLE = 1 MODE1 = 1 MODE0 = 0
MAX781-11
100 90 POWER EFFICIENCY (%) 80 70 60 50 40 30 20 10 1 10 100 BATT = 7.5V SYNC = REF IDLE = 0 MODE1 = 1 MODE0 = 0
100 90 POWER EFFICIENCY (%) 80 70 60 50 40 30 20 10 BATT = 7.5V SYNC = AGND IDLE = 0 MODE1 = 1 MODE0 = 0
100
450 SWITCHING FREQUENCY (kHz) 400 350 300 250 200
1000
1
10
100
1000
3OUT OUTPUT CURRENT (mA)
3OUT OUTPUT CURRENT (mA)
3OUT OUTPUT CURRENT (mA)
6
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SWITCHING FREQUENCY (kHz)
BATT = 5.5V SYNC = REF IDLE = 1 MODE1 = 1 MODE0 = 0
450
100
450 400
PDA/Hand-Held Computer Power Controller
____________________________Typical Operating Characteristics (continued)
(TA = +25C, unless otherwise noted.)
MAX781
3OUT OPERATE MODE POWER EFFICIENCY VARIABLE SWITCHING FREQUENCY
MAX781-09
USING THE BATTERY CHARGER TO DRIVE A CCFL BACKLIGHT ROYER OSCILLATOR
MAX781-01
100 90 POWER EFFICIENCY (%) 80 70 60 50 40 30 20 10 1 10 100 3OUT OUTPUT CURRENT (mA) % kHz BATT = 7.5V SYNC = AGND IDLE = 1 MODE1 = 1 MODE0 = 0
450 CCFL TUBE CURRENT (mA, rms) 400 SWITCHING EFFICIENCY (kHz) 350 300 250 200 150 100 50
2.5 SYNC = REF VCHG = 7V BATT = VCHG - DIODE DROP R4 = 0.47
110 CSBAT AVERAGE VOLTAGE (mV) 100 90 80 70
2.0
1.5 mV 1.0 mA, rms 0.5 0 0 10 20 30 40 50 60 70 CHG6-CHG0 BITS VALUE
60 50 40 30 20 10
0 1000
______________________________________________________________Pin Description
PIN 1-4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 NAME GD2-GD5 VPPA VHI VPPB AGND SYNC CE SCLK DOUT DIN INT FAST COMP CSBAT 5OUT DCHG PGND DLO BST DHI LX FUNCTION High-Side Gate-Driver Outputs VPP-Programming Voltage Output A VPPA, VPPB Linear-Regulator Input Power VPP-Programming Voltage Output B Analog Ground Oscillator Frequency Control and Synchronization Input Serial-Interface Chip-Enable Input--active high Serial-Interface Clock Input Serial-Interface Data Output Serial-Interface Data Input Interrupt Output General-purpose open-drain output Battery-Charger Compensation Battery-Charger Current-Sense Input Linear-Regulated +5V Output Battery-Charger MOSFET Gate-Driver Output Power Ground +3.3V Regulator, Synchronous Rectifier, Gate-Driver Output +3.3V Regulator Boost Capacitor Connection (0.1F to LX) +3.3V Regulator High-Side Gate-Driver Output +3.3V Regulator Inductor Connection
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7
PDA/Hand-Held Computer Power Controller MAX781
_________________________________________________Pin Description (continued)
25 26 27 28 29 30 31 32 33 34 35 36 3OUT CS SS BATT VCHG UVLO REF AOUT TEMP AUXIN --- - ---- SHDN GD1 +3.3V Regulator Feedback Connection and Linear-Regulated + 3.3V Output +3.3V Regulator Current-Sense Input +3.3V Regulator Soft-Start Capacitor Connection Battery Voltage Input Charger Voltage Input Undervoltage Lockout Threshold Input +2.5V Reference Output Analog Multiplexer Buffered Output Analog Multiplexer Input and Battery Sense Input Analog Multiplexer Input Shutdown-Mode Control Input High-Side Gate-Driver Output
+5V LOW CURRENT OUTPUT BATTERY CHARGER DC INPUT C12 VCHG C14 D1 R1 DCHG C1 BATTERY CHARGER SECTION REF R8 SYNC R7 TEMP COMP C10 T C3 C2 CSBAT PGND CS 3OUT R4 CE SCLK DIN DOUT INT FAST AUXIN AOUT UVLO SS C5 AGND VPPA VPPB C8 GD1 GD5 GATE DRIVERS FOR POWER SWITCHING C9 PCMCIA 2.0 CARD SLOT VPPs M2 DLO D5 C6 SHDN 5OUT D7 VHI BATT M3 D3 L1 D2 DHI BST C7 LX T1 +3.3V OUTPUT M1 D6 C11 +14V OUTPUT
MAX781
SPI COMPATIBLE SERIAL INTERFACE
Figure 1. Typical Operating Circuit
8 _______________________________________________________________________________________
PDA/Hand-Held Computer Power Controller MAX781
VCHG +3.3V LINEAR REGULATOR BATT 2.5V REFERENCE REF 3OUT
UVLO
+5V LINEAR REGULATOR CS3 UNDERVOLTAGE SS BST +3.3V SWITCHING REGULATOR DHI LX DLO PGND SYNC
SHDN AGND
CHGSTAT
3VSTAT
INREG
BIAS GEN
VHI VPP LINEAR REGULATORS VPPA VPPB
MODE1
MODE0
AVPP1
AVPP0
BVPP1
BVPP0
IDLE
50N
CE SCLK DIN MUX_ MUXON GDSEL_ GDON CHG_ BATTSTAT CHGON SERIAL INTERFACE
INT DOUT FAST
3
5
7 DCHG
AUXIN AOUT TEMP 5 ANALOG MULTIPLEXER GATE DRIVERS BATTERY CHARGER
COMP CSBAT
Figure 2. MAX781 Block Diagram
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PDA/Hand-Held Computer Power Controller MAX781
_______________Detailed Description
Modes of Operation
Table 1 describes the MAX781's four modes of operation, and Table 2 shows how to select the desired mode. MODE1 and MODE0 are the two bits, out of a total of 32 bits of configuration data, which select the operational mode. See Table 3 for a complete list of the 32 bits of configuration data.
Table 2. Operating Modes
---- ---- SHDN 0 1 1 1 1 1 1 MODE1 x 1 1 0 0 0 1 MODE0 x 1 1 1 1 0 0 CE x 1 0 1 0 x x Resulting Mode Shutdown Operate Low Power (default on power-up) Standby Low Power Standby Operate
Table 1. MAX781 Modes of Operation
MODE DESCRIPTION * Entire chip shut down * All blocks turned off * IQ < 10A * 3OUT, 5OUT, REF off * Default on power-up * 3OUT supplies 10mA at +3.3V linear regulated from BATT * VPP outputs off (VPPA = VPPB = High-Z) * Analog multiplexer off (AOUT = High-Z) * High-side gate drivers off (GD1 = GD2 = GD3 = GD4 = GD5 = 0V) * Battery-charging current source off (DCHG = 5OUT) * 3OUT supplies 10mA at +3.3V linear regulated from BATT * VPP outputs off (VPPA = VPPB = High-Z) * Analog multiplexer enabled * High-side gate drivers off * Battery-charging current source enabled * Buck switching regulator on * 3OUT regulated to +3.3V * VPP outputs enabled * VHI regulated to +14V * Analog multiplexer enabled * High-side gate drivers enabled * Battery-charging current source enabled
Serial Interface
The MAX781 is controlled by 32 bits of configuration data. These 32 bits must be written, MSB first, into the MAX781 using a synchronous serial interface. Table 3 describes the function of each bit of configuration data. To turn the gate drivers on/off, select VPP voltages or program the analog multiplexer. CE, SCLK, DIN, and DOUT are the synchronous serial-interface pins. Figure 3 shows an example of the signal timing necessary to send 32 bits of data to the MAX781. The first six bits clocked out of DOUT are the status bits, and the remaining 26 bits clocked out of DOUT should be ignored. Figure 4 shows the detailed timing requirements of the synchronous serial interface. To write the last eight bits of the configuration data without affecting the rest of the configuration bits, clock eight bits instead of 32 into DIN. This allows the CHARGE, IDLE, MODE1, MODE0, and VPP control bits to be updated in only eight serial clock cycles. As the eight bits are clocked into DIN, the status bits are clocked out of DOUT. Figure 5 shows an example of such a quick access. If eight zeros are sent in a quick access, no configuration data is updated. This allows the status bits to be read quickly without affecting the last byte of configuration data.
Shutdown
Low Power
Standby
Operate
Status Bits
As the 32 bits of serial-configuration data are written into the MAX781, 32 bits of data are read out of DOUT. The first six bits contain status information, and the remaining 26 bits should be ignored. BATTINT and BATTSTAT (Table 3) indicate battery status. It is assumed that the battery pack used with the MAX781 has a thermistor attached to its negative termi-
- ----- -- With S H D N pulled up to the battery voltage, the MAX781 powers on in low-power mode. After powerup, pulling CE high temporaily places the MAX781 into operate mode and allows data to be shifted into the internal shift register. As soon as CE goes low, the MAX781 enters the mode programmed by the MODE1 and MODE0 bits.
10
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PDA/Hand-Held Computer Power Controller MAX781
Table 3. Configuration Data-Bit Assignments
BIT 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 R/W R/W R R/W R R/W R W W W W W W W W W W W W W W W W W W W W W W W W W * 0 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0 0 0 0 1 0 1 0 1 1 1 1 0 0 0 0 NAME BATTINT BATTSTAT 3VINT 3VSTAT CHGINT CHGSTAT GDSEL5 GDSEL4 GDSEL3 GDSEL2 GDSEL1 MUX2 MUX1 MUX0 CHG6 CHG5 CHG4 CHG3 CHG2 CHG1 CHG0 50N FASTON CHARGE IDLE MODE1 MODE0 VPPB1 VPPB0 VPPA1 VPPA0 DESCRIPTION 1 = TEMP pin voltage crossed 0.82* 3OUT 1 = TEMP > 0.82*3OUT, 0 = TEMP < 0.82*3OUT 1 = 3OUT fault detected 1 = 3OUT out of regulation, 0 = in regulation 1 = VCHG > BATT detected 1 = VCHG > BATT, 0 = VCHG < BATT Unused 1 = GD5 sources from VHI, 0 = GD5 sinks to AGND 1 = GD4 sources from VHI, 0 = GD4 sinks to AGND 1 = GD3 sources from VHI, 0 = GD3 sinks to AGND 1 = GD2 sources from VHI, 0 = GD2 sinks to AGND 1 = GD1 sources from VHI, 0 = GD1 sinks to AGND Analog multiplexer bit 2 Analog multiplexer bit 1 Analog multiplexer bit 0 Charger current setting DAC bit 6 Charger current setting DAC bit 5 Charger current setting DAC bit 4 Charger current setting DAC bit 3 Charger current setting DAC bit 2 Charger current setting DAC bit 1 Charger current setting DAC bit 0 1 = 5OUT linear regulator on, 0 = off 1 = FAST sinks current, 0 = FAST open drain 1 = DCHG switching current source on, 0 = off 1 = Idle regulation, 0 = PWM regulation Operating mode select bit, 1, see Table 2 Operating mode select bit, 0, see Table 2 VPPB voltage select bit 1, see Table 5 VPPB voltage select bit 0, see Table 5 VPPA voltage select bit 1, see Table 5 VPPA voltage select bit 0, see Table 5
* = Power-on reset default state
nal, causing the battery pack to need at least three terminals: BATT+, BATT,- and THERM. The MAX781's TEMP pin connects to the battery pack's thermistor (Figure 6). Without the battery pack installed, R8 pulls the MAX781's TEMP pin up to 3OUT, and BATTSTAT = 1. When the battery pack is inserted, the resistive divider formed by the thermistor and R8 pulls the TEMP pin below 3OUT, forcing BATTSTAT = 0. Any transition of BATTSTAT sets BATTINT. Clear BATTINT by writting a logic 1 in bit 31 of the serial-configuration data. The
BATTSTAT comparator is disabled in low-power and shutdown modes, and outputs a logic zero regardless of the state of its inputs. 3VINT and 3VSTAT indicate the status of the 3OUT output (+3.3V 4%). 3OUT is out of regulation when its output voltage falls below +3.1V. 3VSTAT = 0 when 3OUT is in regulation, and 3VSTAT = 1 when 3OUT is out of regulation. A rising edge on 3VSTAT sets 3VINT; thus, 3OUT going out of regulation sets 3VINT.
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PDA/Hand-Held Computer Power Controller MAX781
TIME OUTPUT FROM CPU INPUT TO MAX781 OUTPUT FROM CPU INPUT TO MAX781 CE
SCLK DATA CLOCKED INTO MAX781 ON RISING EDGE OF SCLK
OUTPUT FROM CPU INPUT TO MAX781
DIN
BATTINT
3VINT
VPPA1
VPPA0
DATA CLOCKED OUT OF MAX781 ON FALLING EDGE OF SCLK INPUT TO CPU OUTPUT FROM MAX781 DOUT BATTINT BATTSTAT 3VINT XXX XXX XXX
Figure 3. Serial Configuration Data Example Timing
CE tCP tCSO SCLK tDS tDH DIN tDV DOUT tDO tCL tCSS tCH
***
tCSH tCSW tCS1
*** ***
tTR
***
Figure 4. Detailed Timing Diagram
TIME CE SCLK
DIN
CHARGE
IDLE
MODE1
MODE0
VPPB1
VPPB0
VPPA1
VPPA0
DOUT
BATTINT
BATTSTAT
3VINT
3VSTAT
CHGINT
CHGSTAT
XXX
XXX
XXX
Figure 5. Quick-Access Example Timing
12 ______________________________________________________________________________________
PDA/Hand-Held Computer Power Controller
The 3VSTAT comparator is disabled in the low-power, standby, and shutdown modes, and outputs a logic zero regardless of the state of its inputs. The MAX781 serial-interface outputs are powered from 3OUT. If 3OUT is short circuited to ground, then neither DOUT nor INT will be able to source current. CHGINT and CHGSTAT indicate the status of the charging voltage applied to VCHG. The MAX781 powers itself from either BATT or VCHG, whichever has the higher voltage. CHGSTAT = 0 when BATT is approximately 200mV greater than VCHG. CHGSTAT = 1 when BATT falls below VCHG plus approximately 200mV. Any transition on CHGSTAT sets CHGINT. The CHGSTAT comparator is disabled only in shutdown mode. At power-up, BATTINT is set if the charger is not connected, CHGINT is set if the charger is connected. The INT pin outputs the logical OR of the BATTINT, 3VINT, and CHGINT status bits. The INT pin generates an interrupt on the CPU that controls the MAX781.
MAX781
Supply and Reference
5OUT outputs +5V, linear regulated from either BATT or VCHG, in all modes except shutdown. 5OUT can source up to 25mA. Power comes from BATT as long as the BATT voltage is greater than the VCHG voltage. When the VCHG voltage exceeds BATT, VCHG supplies the 5OUT linear regulator. The MAX781's internal circuitry is powered from 5OUT. When the DLO pin drives high, it sources current from 5OUT. The DOUT and INT pin output drivers are powered from 3OUT. If an external 5V supply is available and connected to the 5OUT pin, the 5OUT linear regulator can be disabled by clearing the 5ON bit. If 5ON is cleared without an external +5V supply connected to 5OUT, or if 5OUT is shorted to ground, the MAX781 internal registers will be cleared to their power-on state.
Table 4. Status Detection in the Four Operating Modes
MODE STATUS BIT Shutdown BATTSTAT 3VSTAT CHGSTAT Disabled Disabled Disabled Low Power Disabled Disabled Enabled Standby Enabled Enabled Enabled Operate Enabled Enabled Enabled
3.3V Output
3OUT outputs +3.3V in all modes except for shutdown. In low-power and standby modes, 3OUT is linear regulated from either BATT or VCHG, whichever has the higher voltage. In operate mode, the switch-mode buck (step-down) converter is activated to regulate 3OUT to 3.3V. In operate mode, the 3OUT linear regulator is off.
BATT 3OUT TO ANALOG MULTIPLEXER BATTERY PACK BATT+ THERM R8 RTEMP TEMP 83k COMPARATOR DISABLED IN LOW-POWER MODE; OUTPUTS "0" REGARDLESS OF STATE OF INPUTS
WRITING A "1" TO BATTINT CLEARS THE FLIP FLOP CLR D > > Q BATTINT
BATTSTAT T
BATT-
1F
14.1k
MAX781
R4 AGND, PGND 402k
Figure 6. BATTINT, BATTSTAT Status Circuitry
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PDA/Hand-Held Computer Power Controller
DHI high-side drives an external N-channel power MOSFET, M1. Inside the MAX781, the DHI driver is well-isolated so it can be powered separately from the rest of the chip. The DHI driver is powered by current that flows into BST and out of LX. Thus, BST is the "power" connection and LX is the "ground" connection for the DHI driver. An internal level shifter allows the MAX781 internal circuitry to communicate with the DHI driver. RSENSE, connected from CS to 3OUT, senses current in the primary of transformer T1. With no load on VHI, the primary of T1 can be treated as the inductor in a current-mode buck converter. RSENSE detects current in the primary and turns off M1 when the current limit is reached. The current limit is adjusted to ensure that 3OUT stays at 3.3V. With M1 off, M2 stays on until the voltage on RSENSE reaches zero. There is an absolute current limit that protects the output in the event 3OUT is short circuited to ground. When the voltage from 3OUT to CS reaches 100mV, M1 is turned off whether or not 3OUT is in regulation. A capacitor (C5) on the soft-start (SS) pin allows the current limit to slowly ramp up when power is first applied. A 4A current source from 3OUT feeds the SS pin. The ramp time to full current limit is approximately 1ms for every nanofarad of capacitance on SS, with a minimum value of 10ns. Once the SS pin reaches 3.3V, the maximum peak current is available. UVLO prevents the buck regulator and battery charger from switching if 5OUT is out of regulation. The voltage on UVLO is compared to REF. If UVLO is greater than REF, the buck regulator and battery charger will function normally. With UVLO less than REF, the buck regulator and battery charger stay off and the low-power mode linear regulator supplies 3OUT, whether or not operate mode has been set. Tying UVLO to AGND allows an internal resistive divider to feed the UVLO comparator, preventing operation of the buck regulator and battery charger for 5OUT voltages less than approximately 4.35V (see the Electrical Characteristics). The MAX781 3.3V buck regulator is similar to the 3.3V buck regulator on the MAX783. For further information, refer to the MAX783 data sheet regulation scheme used for load current below about 25% of current limit. Idle-ModeTM regulation pulses M1 until 25% of the absolute current limit is reached, at which point M1 turns off. M1 does not turn on again until 3OUT falls below 3.3V. This scheme improves light-load efficiency by minimizing the number of times M1 needs to be turned on to keep 3OUT in regulation. However, the operating frequency varies with load. At load currents above 25% of current limit, the regulator uses resonant frequency PWM regulation independent of the idle bit. PWM regulation turns M1 on at a constant frequency and modulates M1's duty cycle to maintain the current required to keep 3OUT in regulation. The switching frequency remains constant regardless of the load current. Operating with a constant frequency results in lower amplitude and more easily filtered output ripple. The SYNC pin either sets the internal switching frequency or synchronizes the MAX781 to an external oscillator. Tying SYNC to REF sets a switching frequency of 300kHz. Tying SYNC to 5V or AGND sets a 230kHz switching frequency. Driving SYNC with an external oscillator synchronizes the PWM switching with the external oscillator.
MAX781
VPP Regulator
VPPA and VPPB linear regulate VHI down to 0V/+3.3V/+5V/+12V for use as a PCMCIA VPP voltage. The VPPB0, VPPB1, VPPA0, VPPA1 bits control the VPPB and VPPA output voltage. Programming VPPA or VPPB to 0V shuts off the linear regulator and saves quiescient supply current. Table 5 shows how to program the VPPA and VPPB control bits. During the flyback phase of the buck converter (DLO on), VHI loads 3OUT. As long as DLO is on, power can be supplied to VHI. When 3OUT has a light load, DLO may not stay on long enough to supply power to VHI. To prevent VHI from sagging, an internal comparator checks VHI. If VHI sags below 12.8V, DLO is turned on for 1s to provide power to VHI, regardless of the voltage on RSENSE. Power can only be delivered to VHI in operate mode when the buck switching regulator is active. The VHI pin includes an overvoltage clamp that sinks current if VHI exceeds 19V. This prevents the parasitic capacitance in transformer T1 from causing the VHI voltage to climb without limit.
Idle Regulation vs. PWM Regulation In operate mode, 3OUT can be regulated using pulseskipping (Idle-ModeTM regulation) or pulse-width-modulation (PWM) regulation. The IDLE bit selects the
TMIdle-Mode is a trademark of Maxim Integrated Products.
14 ______________________________________________________________________________________
PDA/Hand-Held Computer Power Controller
Table 5. VPPA and VPPB Control Bits
VPPA1 0 0 1 1 VPPB1 0 0 1 1 VPPA0 0 1 0 1 VPPB0 0 1 0 1 VPPA Voltage (V) 0 5 12 3.3 VPPB Voltage (V) 0 5 12 3.3
Battery Charger
The battery charger is a voltage-mode average current regulator. Figure 8 shows a functional diagram of the battery charger circuitry. The GMAMP is a transconductance amplifer with approximately 62dB of openloop DC gain. Set the GMAMP bandwidth with the capacitor on COMP. GMAMP bandwidth in hertz = gm / C where gm = 0.0006 mho (mho = 1/) and C = capacitance on COMP in farads. Average the current-sense signal by setting the GMAMP bandwidth much lower than the battery-charger switching frequency. The voltage output of the GMAMP at COMP is converted to a duty cycle, which is driven out of DCHG. Serial-configuration bits CHG6-CHG0 set the average current level. When CHG6-CHG0 are all set (1111111), CSBAT is regulated to an average of 200mV. When CHG6-CHG0 equals binary 0111111, CSBAT is regulated to an average of 100mV.
CHG6-CHG0
MAX781
Gate Drivers
GD1 through GD5 are gate-driver outputs that highside drive external N-channel power MOSFETs. Loads connected to 3OUT can be connected or disconnected by using the circuitry shown in Figure 7. Clearing GDSEL1 (GDSEL1 = 0) causes GD1 to sink up to 450A to AGND. Setting GDSEL1 (GDSEL = 1) causes GD1 to source up to 10A from VHI. GD2-GD5 operate the same way. VHI is active (i.e., regulated to at least 12.8V) only in operate mode, so the gate drivers also only function in operate mode. GDSEL1 defaults to a 1 on power-up. GDSEL2 through GDSEL5 default to 0 on power-up. FAST is a general-purpose output pin that sinks current when FASTON = 1 and goes open drain when FASTON = 0. FAST can be pulled up to any voltage up to 19V. To use FAST as a general-purpose 3.3V logic output, pull it up to 3OUT with a 100k resistor. FAST may be used to pull the gate of M3 down to connect the battery to the input supply. The MAX781 does not limit the battery current when FAST is used in this way.
...TO REST OF 3OUT CIRCUIT 3OUT GD_ N-CHANNEL POWER MOSFET
DACOUT (0mV TO 200mV) 7-BIT DAC
5OUT AT 0% DUTY CYCLE, DCHG = 5OUT VOLTAGE TO DUTY CYCLE CONVERTER DCHG = 5OUT EXTERNAL SWITCH OFF DCHG DCHG = AGND EXTERNAL SWITCH ON PGND
GMAMP CSBAT COMP
Figure 8. Battery-Charger Block Diagram
Analog Multiplexer
The MAX781's built-in buffered analog multiplexer selects one of eight different signal sources to be output from the AOUT pin. Figure 9 shows the analog multiplexer circuitry. The AOUT buffer amplifier is disabled in the shutdown and low-power modes, leaving the 89.7k resistor to pull AOUT down to ground. Program the MUX0, MUX1, MUX2 bits in the serial-configuration data to select the analog multiplexer channel (Table 6). Resistive dividers in the signal paths scale the channels to ensure that AOUT is scaled to REF. The AOUT buffer amplifier can sink or source 1mA.
MAX781
3.3V LOAD THAT NEEDS TO BE TURNED ON/OFF AGND ...TO REST OF AGND CONNECTIONS
Figure 7. Using the Gate Drivers for High-Side Load Switching
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PDA/Hand-Held Computer Power Controller MAX781
Table 6. Analog Multiplexer Channel Selection
MUX2 1 1 1 1 0 0 0 0 MUX1 1 1 0 0 1 1 0 0 MUX0 1 0 1 0 1 0 1 0 AOUT OUTPUTS AUXIN/1.5 REF VPPB/5.3 VPPA/5.3 TEMP/1.5 BATT/5 5OUT/2.2 3OUT/1.5
_Component Selection and Layout
3.3V Output
Input and Output Bypass Capacitors Capacitor C15 ensures that the buck regulator has a low AC-impedance power source. C15's root mean square ripple-current rating must be greater than 0.5 x (maximum power output capability of the system) / 3.3V. Capacitor C6 keeps 3OUT output ripple low and stabilizes the regulation loop. C15 and C6 must have low equivalent series resistance (ESR), preferably with less than 0.2 of ESR at 200kHz. Tantalum capacitors typically have the lowest ESR. C15's ground connection must be as close as possible to C6's ground connection; ideally, the two capacitors will be grounded at the same point. The MAX781's AGND pin should only connect to system ground at the ground connection of C15 and C6. If the PC board has a ground plane, a separate trace should directly connect AGND to the ground connections of C15 and C6. Likewise, the BATT pin should only connect to the battery at C15's positive terminal. The capacitance and ESR of C6 determine loop stability. To ensure loop stability, the minimum capacitance and maximum ESR values are: C6 > 2.5V / (3.3V x R7 x 2 x p x GBWP) with C6 specified in Farads, R7 specified in ohms, GBWP = gain bandwidth product of 60,000Hz, and: C6 ESR < (3.3V x R7) / 2.5V with C6 ESR specified in ohms, and R7 specified in ohms. In order to achieve the required low ESR, it may be appropriate to select a value greater than the minimum for C6, or to construct a composite C6 by paralleling several smaller capacitors.
AUXIN
REF
498.4k
VPPB
116k
498.4k
VPPA
116k
TEMP
500k
BATT
359k 125k
200k
5OUT
183.3k
150k
3OUT
300k
AOUT
Y0 Y1 MUX0 MUX1 MUX2 A0 A1 A2 3-to-8 DECODER Y2 Y3 Y4 Y5 Y6 Y7
89.7k
Figure 9. Analog Multiplexer Circuitry
16
Current-Sense Resistor Current-sense resistor R7 sets the maximum peak current through power switch M1 and the primary of transformer T1. The MAX781's maximum peak current limit is 120mV / R, where R is the minimum possible resistance for R7, and 120mV is the maximum electrical specification for the current-limit threshold. For example, selecting a 0.082 1% resistor for R7 yields a maximum peak current limit of 120mV / 0.082 x 0.99 = 1.478A. The maximum peak current limit must be less than or equal to the maximum allowed continuous DC current through either M1 or the primary of T1. R7 also determines how much power 3OUT, VPPA, and VPPB can deliver. The current-limit threshold can be as small as 80mV and, using a 0.082 1% resistor,
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PDA/Hand-Held Computer Power Controller
R7 can be as large as 0.082 x 1.01 = 0.0828, yielding a minimum peak current limit of 80mV / 0.0828 = 0.966A. Use the spreadsheet in Listings 1 and 2 to calculate the power available at 3OUT as a function of the currentsense resistor choice.
C13: +C6 B14: +B7 C15: +C8 C16: +C9 C21: @MIN(+C15/C16*C13*(C16-C15)/B14,B12) C22: +B12-C21 C23: @IF(C22=0,0.5*(B14/1000000)*C21^2*1000000/ C13/C15,C22+C21/2) C24: +C15*(C18+1)*C17/1000 C25: +C23-C24/(C19/100)/C15
MAX781
Listing 1. Spreadsheet for Calculating 3OUT Current Capability Parameter (Cell A1)
Current-Limit Threshold Current Sense R7 Current Limit Switching Frequency Switching Period T1 Primary Inductance 3OUT Regulation Point BATT Input Range (Cell A10) Current Limit Switching Period T1 Primary Inductance 3OUT BATT VHI Load Current T1 Turns Ratio T1 Coupling Loss (Cell A20) T1 Ripple Current T1 Continuous Current 3OUT Current, No VHI load VHI Load Power 3OUT Guaranteed Current (Cell A26) (Cell B26) 0.638 0.325 0.645 0.926 0.307 (Cell C26) A A A W A 16 3.430 17.500 60 3.5 80 % mA 0.964 3.704 A s H
Min Max U n i t s (Cell B1) (Cell C1)
80 81 0.964 270 2.941 16 3.170 5.000 120 83 1.481 340 3.704 24 3.430 17.500 mV m A kHz s H V V
R7 must have as little series inductance as possible and be as physically small as possible. 3OUT and CS3 need to Kelvin sense R7. A pair of traces running in parallel should leave 3OUT and CS3 and diverge only when they meet R7. Minimize the distance between R7 and the positive terminal of C6.
Power MOSFETs M1 and M2 must be logic level, low rDS(ON), N-channel power MOSFETs. M1's drain should be as close as possible to C15's positive terminal and M2's source should be as close as possible to C15's ground connection point. Transformer T1 T1's primary inductance must be between 10H and 100H. The peak current allowed through the primary with the secondary open circuited must be greater than the worst-case peak current set by R7. T1's turns ratio (number of turns on secondary / number of turns on primary) should be 3.5. If VHI rises up to 20V when 3OUT is loaded in operate mode, T1 may have too much interwinding capacitance. Minimize interwinding capacitance to prevent energy waste in the VHI clamp (which clamps VHI to 19V to protect the MAX781).
__________Applications Information
Design Example
Table 7 shows the targets for a typical design requirement. Since both PCMCIA slots will not be programmed at the same time, VPPA and VPPB will never be at +12V at the same time; thus the worst case for power consumption is when both 3.3V and VPPA or VPPB is fully loaded. Total power consumption = (max 3OUT voltage) x (max 3OUT load current) + (VHI voltage) x (max VPP or load current) / (transformer efficiency).
Listing 2. Calculating 3OUT Current-Capability Formulas
B4: +B2/C3 C4: +C2/B3 B6: 1/C5*1000 C6: 1/B5*1000 B12: +B4
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17
PDA/Hand-Held Computer Power Controller MAX781
Table 7. Specifications for a Typical Design
PARAMETER Input Power 3.3V Output Current VPPA Output Current VPPB Output Current Charge Current +12V output when programming flash memory in Slot A +12V output when programming flash memory in Slot A Digitally programmable DESIGNATION 5 NiCD cells 15V DC adapter MIN 5 17.5 300 MAX UNITS V mA
Table 8. Dale Electronics M/N LPE-6562-A070 Specifications
PARAMETER Primary Inductance Leakage Inductance (at 0.1VRMS, 100kHz) Primary Continuous DC Current MIN 16 TYP 20 MAX 24 0.03 2.6 0.075 0.51 3.5 UNITS H H A
60
mA
Primary DC Resistance Secondary DC Resistance Turns Ratio (secondary/primary)
60
mA
0
1
A
VPPA and VPPB are linear regulated from VHI, so the power consumed by loads on VPPA or VPPB equals the VHI voltage times the load current. Barring a Schottky diode drop, VHI equals the 3OUT voltage x (1 + turns ratio). With the specifications of Table 7 and an 80% transformer efficiency, the total power consumption works out to 2.037W; thus the average current through the primary of T1 is 594mA. The peak current through the primary of T1 will depend on the minimum primary inductance. As a rule of thumb, the peak current will be about 1.5 times the average current. For an average current of 594mA, the peak current would be about 900mA. To achieve a 900mA peak current, select R7 to be 80mV / 900mA = 0.088. The closest comercially available value would be 0.082 1%. The spreadsheet in Listing 1 calculates how high a guaranteed output current can be, given commercially available component values, and taking component tolerances into account. Table 8 shows the electrical specifications for a transformer that meets the requirements of Listing 1. Power MOSFETs M1 and M2 should have an on-resistance at logic-level gate drive (rDS(ON) at VGS = 4.5V)
of the same order as T1's primary DC resistance. The Siliconix Si9955DY dual N-channel MOSFET satisfies this requirement with a 0.2 maximum on-resistance per device. Table 9 lists the bill of materials for an example circuit that fulfills the requirements of Table 7.
Driving a CCFL Backlight Royer Oscillator
The digitally adjustable current from the battery charger can be used to drive a Royer oscillator. The Royer oscillator is a resonant circuit fed by a constant current. The root mean square current out of the secondary winding of the Royer transformer is proportional to the current fed into the center tap of the Royer transformer. Figure 10 shows the application circuit. The diode from VCHG to BATT keeps BATT from dropping too far below 5OUT, which causes excess supply current. Figure 11 shows how the programmed current corresponds to the CCFL root mean square tube current. The NPN transistor connected to COMP and the zener diode protects the transformer from an open-tube condition by shutting off the Si9953DY if pin 2 of the CTX110606 exceeds 0.6V + 10V + 0.6V. This limits the voltage on the secondary to 11.2 x 171 x 2 = 3830.4V peak-to-peak = 1354V RMS , which is well within the CTX110606 maximum secondary voltage specification of 2010VRMS.
18
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PDA/Hand-Held Computer Power Controller MAX781
Table 9. Design Example Bill of Materials
SYMBOL T1 L1 M1, M2 M3 R1 R4 R7 R8 C1 C2 C3 C5 C6 C7 C8 C9 C10 C11 C12 C14 D1 D2 D3 D5 D6 D7 DESCRIPTION transformer 47H, 1.5A IDC inductor N-Channel MOSFETs P-Channel MOSFET 100k, 20% resistor 0.2, 1% resistor 0.082, 1% resistor 10k, 1% resistor 0.1F, 20V capacitor 0.33F, 6V capacitor 1F, 6V capacitor 0.01F, 6V capacitor 120F, 6.3V capacitor, 0.09 ESR at 100kHz 0.1F, 10V capacitor 1F, 16V capacitor 1F, 16V capacitor 22F, 25V capacitor 2.2F, 25V capacitor 1F, 6V capacitor 22F, 25V capacitor 20V 1N4150 type diode 20V Schottky diode 20V Schottky diode 20V Schottky diode 50V Schottky diode 20V 1N4150 type diode PART No. M/N LPE-6562-A070 CDR125-470 Si9955DY Si9953DY MANUFACTURER Dale Sumida Siliconix Siliconix IRC IRC
195D127X06R3R2T
Sprague
195D226X0025R2T
Sprague
195D226X0025R2T CMPD4150 EC10QS03 EC15QS03 EC10QS03 EC10QS05 CMPD4150
Sprague Central Nihon Nihon Nihon Nihon Central
Table 10. Component Suppliers
SUPPLIER Central Semiconductor Coiltronics Dale IRC Nihon Rep: Quantum Marketing Siliconix Sprague Sumida Wilhelm Westerman Rep: Inter-Technical Group Zetex PHONE (516) 435-1110 (407) 241-7876 (605) 665-9301 (213) 772-2000 Japan 81-3-3494-7411 USA (805) 867-2555 (800) 554-5565 (603) 224-1961 (708) 956-0666 Germany 0621-408012 USA (914) 347-2474 USA (516) 543-7100 UK 061-627-4963 FAX (516) 435-1824 (407) 241-9339 (605) 665-1627 (213) 772-9028 81-3-3494-7414 (805) 867-2698 (408) 970-3950 (603) 224-1430 (708) 956-0702 0621 403538 (914) 347-7230 (516) 864-7630 061-627-5467
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19
PDA/Hand-Held Computer Power Controller MAX781
BATT CMPD4448 VCHG CMPT3904 CMPZ5240B 0.33F 10k 15pF 2kV CCFL CMPD4448
M1 DRAIN
COMP
MAX781
10k
CMPD4448 2 Si9953DY DCHG 0.1F 22F 20V CTX150-4 1 2 710 EC10QS02L MKS01-SMD CCFL 0.1F 3 4 5 CTX110606 10
FMMT619
FMMT619
CSBAT
0.47
AGND
NOTE: SEE TABLE 10 FOR COMPONENT SUPPLIER INFORMATION. CM = CENTRAL SEMICONDUCTOR CT = COILTRONICS EQ = NIHON INTER ELECTRIC CORP. FM = ZETEX MK = WILHELM WESTERMANN
Figure 10. Digitally Adjustable CCFL Backlight Circuit
20
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PDA/Hand-Held Computer Power Controller
Interfacing the MAX781 to an IBM Compatible PC
Figure 1 shows the MAX781 typical operating circuit. On power-up, with 4.8V < BATT < 18V and CE = SCLK = DIN = 0V, the MAX781 is in low-power mode. 3OUT outputs +3.3V linear regulated from BATT, and REF outputs +2.5V. INT should output a 3.3V logic high. Neither DHI nor DLO should be switching. Serial data must be sent to the MAX781 in order to change modes. The parallel printer interface on a personal computer can be used to send serial control data to the MAX781. Listing 3 shows a simple Microsoft Quick Basic program for communicating with the MAX781 over the LPT1 parallel interface port.
MAX781
21
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PDA/Hand-Held Computer Power Controller MAX781
Listing 3. MAX781 Control Program in QBasic
22
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PDA/Hand-Held Computer Power Controller
__________________Pin Configuration
TOP VIEW
GD2 GD3 GD4 GD5 VPPA VHI VPPB AGND SYNC 1 2 3 4 5 6 7 8 9 36 GD1 35 SHDN 34 AUXIN 33 TEMP
___________________Chip Topography
GD4 GD3 GD2 GD1 SHDN TEMP AUXIN AOUT REF UVLO VHI
MAX781
GD5
VPPA
MAX781
32 AOUT 31 REF 30 UVLO 29 VCHG 28 BATT 27 SS 26 CS 25 3OUT 24 LX 23 DHI 22 BST 21 DLO 20 PGND 19 DCHG
VPPB AGND SYNC CE SCLK
VCHG BATT 0.219" (5.563mm) SS CS 3OUT
CE 10 SCLK 11 DOUT 12 DIN 13 INT 14 FAST 15 COMP 16 CSBAT 17 5OUT 18
DOUT DIN INT
LX
DHI FAST CSBAT COMP 5OUT DLO PGND 0.152" (3.861mm) DCHG
BST
SSOP
TRANSISTOR COUNT: 2661 SUBSTRATE CONNECTED TO AGND.
______________________________________________________________________________________
23
PDA/Hand-Held Computer Power Controller MAX781
________________________________________________________Package Information
DIM A A1 B C D E e H L INCHES MAX MIN 0.104 0.094 0.011 0.004 0.017 0.011 0.012 0.009 0.610 0.604 0.298 0.292 0.032 BSC 0.416 0.398 0.035 0.020 8 0 MILLIMETERS MIN MAX 2.39 2.64 0.10 0.28 0.30 0.44 0.23 0.32 15.34 15.49 7.42 7.57 0.80 BSC 10.10 10.57 0.51 0.89 0 8
21-0032A
E
H
D A
0.127mm 0.004in.
e
B
A1
C
L
36-PIN PLASTIC SHRINK SMALL-OUTLINE PACKAGE
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
24 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 (c) 1994 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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