Rainbow Electronics MAX781 User Manual

19-0205; Rev 0; 7/94

EVALUATION KIT

AVAILABLE

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/Microwire™ 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 Mode™ 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 50µF 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

♦ +3.3V Step-Down Controller
♦ Dual PCMCIA 2.0 Compatible VPP Outputs

(0V/3.3V/5V/12V)

♦ Digitally Adjustable Switching Current Source for

Battery Charging

♦ 5 High-Side Switch Gate-Driver Outputs
♦ SPI Serial Interface
♦ 300kHz Switching Frequency
♦ Oscillator SYNC Input
♦ 2.5V ±1.5% Reference Output
♦ 36-Pin SSOP Package

________________________Applications

Subnotebook Computers
PDAs
Communicating Computers
Handy-Terminals

______________Ordering Information

PART

MAX781CBX
MAX781EBX -40°C to +85°C

TEMP. RANGE PIN-PACKAGE

0°C to +70°C

36 SSOP
36 SSOP

________________________________________________Typical Application Diagram

(up to 18V)

5 to 8

NiCd/NiMH

CELLS 

or
2 LION
CELLS

DCIN

DIGITALLY

ADJUSTABLE

SWITCHING

CURRENT

SOURCE

MAX781

HIGH-SIDE GATE DRIVERS


5



+3.3V AT 1A OR MORE


SERIAL INTERFACE

4

INTERRUPT

VPPA

VPPB

ANALOG MULTIPLEXER OUTPUT

SUBSYSTEMS

LOAD 

SWITCHES

SELF REFRESH

DRAM

CPU

PCMCIA
SLOT A

PCMCIA
SLOT B

ADC

MAX781

Pin Configuration on last page.

™

SPI 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

Call toll free 1-800-998-8800 for free samples or literature.

1

PDA/Hand-Held Computer Power Controller

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

MAX781

All Other Pins to AGND or PGND ..................................-0.3V, 7V

VPPA, VPPB Current.........................................................100mA

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= T

MIN

to T

, unless otherwise noted.)

MAX

5OUT Current....................................................................100mA

3OUT Current......................................................................40mA

Continuous Power Dissipation (T

SSOP (derate 11.76mW/°C above +70°C) ....................941mW

Operating Temperature Ranges

MAX781CBX .........................................................0°C to +70°C

MAX781EBX......................................................-40°C to +85°C

Storage Temperature Range.............................-65°C to +150°C

Lead Temperature (soldering, 10sec).............................+300°C

= +70°C)

A

SUPPLY AND REFERENCE

BATT Quiescent Supply Current

5OUT Output Voltage

Internal Undervoltage Lockout
Threshold (measured at 5OUT,
UVLO = AGND)

UVLO Threshold
(measured at UVLO)

INTERNAL OSCILLATOR

Internal Oscillator Frequency

CONDITIONS

Shutdown mode, –S—H—D—N–= 0V
Low-power mode, –S—H—D—N–= BATT = 18V
Standby mode, –S—H—D—N–= BATT = 18V
Operate mode, –S—H—D—N–= BATT = 18V
No load
I

= -20µA to 100µA

SOURCE

Operate or standby mode, 5.5V < BATT < 18V,
0mA < I

Low-power mode, 5.5V < BATT < 18V,
0mA < I

V

5OUT

V

5OUT

V

UVLO

V

UVLO

SYNC = REF
SYNC = AGND or 5OUT

5OUT

5OUT

rising
falling

rising
falling

< 25mA

< 10mA

10

60 120

250 750

4.8 5.2

4.8 5.2

4.30 4.60 4.80

4.10 4.35 4.50
97 103

90 96

270 300 340
170 230 260

UNITSMIN TYP MAXPARAMETER

µA

mA12

V2.463 2.5 2.537REF Output Voltage

mV-20 20REF Load Regulation

V

V

%REF

nA50UVLO Input Bias Current

kHz
kHz270 350SYNC Capture Range (Note 1)

ns500SYNC Minimum Pulse Width (Note1)
ns200SYNC Fall Time (Note 1)
µs1SYNC Rise Time (Note 1)

V0.75SYNC Input Voltage Low
V3.8SYNC Input Voltage High

nA-100 100SYNC Leakage Current

2 _______________________________________________________________________________________

PDA/Hand-Held Computer Power Controller

ELECTRICAL CHARACTERISTICS (continued)

(BATT = 6V, power-on reset state, TA= T

3.3V OUTPUT

DLO On-Resistance

BATTINT Battery-Detect
Threshold (measured at TEMP)

VPP REGULATOR

VPP_Output Voltage

HIGH-SIDE GATE DRIVERS

to T

MIN

Low-power mode, 4V < BATT < 18V, 0mA < I
Standby mode, 4V < BATT < 18V, 0mA < I

Operate mode, 4V < BATT < 18V,
CS to 3OUT = 0mV to 80mV

3OUT falling

High, 5OUT = 4.75V
Low, 5OUT = 4.75V
High or low, BST - LX = 4.5V
TEMP falling
TEMP rising

Operate mode V12.8 13.5 14.2VHI Regulation Threshold

Operate mode,
I

SINK

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

I

SINK

VPP_1 = 0, VPP_0 = 0

14.2V < VHI < 18V, VPP_1 = 0, VPP_0 = 1,
0mA < IVPP_ < 60mA

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

VHI = 14.2V, GDSEL_ = 1,
I

SOURCE

VHI = 14.2V, GDSEL_ = 0,
I

SINK

GD_ = 2.5V, GDSEL_ = 1,
VHI = 14.2V

GD_ = 2.5V, GDSEL_ = 0,
VHI = 14.2V

, unless otherwise noted.)

MAX

= 200µA,

= 1mA,

= 1µA

= 20µA

CONDITIONS

3OUT

3OUT

< 1mA

< 10mA

3.17 3.43

3.17 3.43

3.17 3.43

15
10

75 81

83 89

0.25

4.75 5.0 5.25

11.4 12.0 12.6

3.14 3.3 3.49

MAX781

UNITSMIN TYP MAXPARAMETER

V3OUT Output Voltage

mV80 100 130CS to 3OUT Current-Limit Threshold

V2.9 3.0 3.13VINT Fault-Detect Threshold

mV1503VINT Fault-Detect Hysteresis

Ω
Ω10DHI On-Resistance

%3OUT

V20VHI Clamp Voltage

mA1VHI Clamp Current

µA45VHI Input Bias Current

V

V14GD_ Output High Voltage

V0.25GD_ Output Low Voltage

µA61018GD_ Source Current

µA200 450 900GD_ Sink Current

_______________________________________________________________________________________ 3

PDA/Hand-Held Computer Power Controller

ELECTRICAL CHARACTERISTICS (continued)

(BATT = 6V, power-on reset state, TA= T

ANALOG MULTIPLEXER

MAX781

AOUT Output Voltage

SERIAL INTERFACE

CE, SCLK, DIN Logic Input High
Voltage

CE, SCLK, DIN Logic Input Low
Voltage

DOUT, INT Logic Output High
Voltage

DOUT, INT Logic Output Low
Voltage

CE, SCLK, DIN Logic Input
Rise/Fall Time (Note 1)

BATTERY CHARGER

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

to T

MIN

MUX2 = 0, MUX1 = 0, MUX0 = 0
MUX2 = 0, MUX1 = 0, MUX0 = 1
MUX2 = 0, MUX1 = 1, MUX0 = 0
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
I

SINK

I

SOURCE

I

SINK

High or low, 5OUT = 4.75V
CHG6 to CHG0 = 1,

CHARGE = 1

CSBAT = 0V mV-2 0 2

FAST = 3V, FASTON = 1
FAST = 18V, FASTON = 0

, unless otherwise noted.)

MAX

= 10µA

= 1mA

= 1.6mA

CONDITIONS

UNITSMIN TYP MAXPARAMETER

%3OUT65.33 66.67 68.00
%5OUT44.54 45.45 46.36

%BATT19.90 20.00 20.10

%TEMP65.33 66.67 68.00

%VPPA18.49 18.87 19.25
%VPPB18.49 18.87 19.25
%VREF99.8 100 100.2

%AUXIN65.33 66.67 68.00

mV10AOUT Output Low

V2

V0.8

nA-100 100SCLK, DIN Leakage Current
kΩ60 100 140CE Internal Pull-Down Resistance

V2.7

V0.4

ns50

Ω10DCHG On Resistance

mV190 200 210

µmho400 600 750

mA1.0 2.0

nA±1.0

4 _______________________________________________________________________________________

PDA/Hand-Held Computer Power Controller

TIMING CHARACTERISTICS (Note 1)

PARAMETER MIN TYP MAX UNITS

DIN to SCLK Data Setup Time 125 ns
DIN to SCLK Data Hold Time
SCLK to DOUT Valid Propagation Delay 30 200 ns
SCLK Clock Period 400 ns
SCLK High Pulse Width 125 ns
SCLK Low Pulse Width 125 ns
CE Assertion to DOUT Enable 120 ns
CE Deassertion to DOUT Disable 120 ns

CE Assertion to SCLK Rising-Edge
Setup Time

SCLK Rising Edge to CE Deassertion 200 ns
CE High Pulse Width 300 ns
SCLK Rising Edge to CE Assertion 200 ns
CE Deassertion to SCLK Rising Edge 200 nst

Note 1: Guaranteed by design.

SYMBOL

t

DS

t

DH

t

DO

t

CP

t

CH

t

CL

t

DV

t

TR

t

CSS

t

CSH

t

CSW

t

CS0
CS1

0 ns

200 ns

__________________________________________Typical Operating Characteristics

(TA = +25°C, unless otherwise noted.)

MAX781

NO LOAD SUPPLY CURRENT

10

1

0.1

(I

=0mA)

3OUT

SYNC=UVLO=AGND,
CHARGE=0
GDSEL_=0

0.01

QUIESCENT CURRENT (mA)

MUX_=0
5ON=1
VPP_=0

0.001
2 4 6 8 10 12 14 16 18



OPERATE MODE (IDLE = 0)

OPERATE MODE (IDLE = 1)

STANDBY MODE

LOW-POWER MODE

SHUTDOWN MODE

BATT INPUT VOLTAGE (V)

MAX781-01

CHARGER OUTPUT CURRENT

1000

100

CURRENT INTO BATT (mA)

10

1

3 7 15 31 12763

CHARGER CODE (CHG6–CHG0 VALUE)



%

mA

R4 = 0.2Ω
SYNC = AGND
BATT = 7V TO 8V
VCHG = 12V

100
90

MAX781-03

80
70

60
50
40
30
20

10

_______________________________________________________________________________________ 5

EFFICIENCY (%)

PDA/Hand-Held Computer Power Controller

____________________________Typical Operating Characteristics (continued)

(TA = +25°C, unless otherwise noted.)

VPPA AND VPPB OUTPUT POWER

VPPA SHORTED TO VPPB AND

400

MAX781

350

300
250

200

CURRENT (mA)

150

100

CLAMPED TO 11.5V

VPPA + VPPB CURRENT

CONFIGURATION = $FF, $00, $02, $6A,
SYNC = AGND, NO 3OUT LOAD
T1 TURNS RATIO (SECONDARY
TURNS / PRIMARY TURNS) = 3.5

50

4

6 8 10 12 14 16 18

VHI VOLTAGE

BATT INPUT CURRENT

BATT VOLTAGE (V)

14.0

MAX781-02

13.5

13.0

12.5

12.0

11.5

11.0

10.5

DCHG DUTY CYCLE vs. COMP VOLTAGE

90

AT 0% DUTY CYCLE,

80

DCHG = 5OUT

70
60
50
40

VHI VOLTAGE (V)

30

DCHG DUTY CYCLE (%)

20
10

0

0.5 1.0 1.5 2.0 2.5 3.0

0



COMP VOLTAGE (V)

MAX781-04

3OUT OPERATE MODE POWER EFFICIENCY

(FIXED 300kHz SWITCHING FREQUENCY)

100

BATT = 5.5V

90

SYNC = REF
IDLE = 0

80

MODE1 = 1
MODE0 = 0

70
60

50
40

POWER EFFICIENCY (%)

30
20

10

1 10 100 1000

3OUT OUTPUT CURRENT (mA)

MAX781-05

3OUT OPERATE MODE POWER EFFICIENCY

(FIXED 230kHz SWITCHING FREQUENCY)

100

BATT = 5.5V

90

SYNC = AGND
IDLE = 0

80

MODE1 = 1
MODE0 = 0

70
60

50
40

POWER EFFICIENCY (%)

30
20

10

1 10 100 1000

3OUT OUTPUT CURRENT (mA)

3OUT OPERATE MODE POWER EFFICIENCY

(FIXED 300kHz SWITCHING FREQUENCY)

100

BATT = 7.5V

90

SYNC = REF
IDLE = 0

80

MODE1 = 1
MODE0 = 0

70
60

50
40

POWER EFFICIENCY (%)

30
20

10

1 10 100 1000

3OUT OUTPUT CURRENT (mA)

MAX781-06

MAX781-08

3OUT OPERATE MODE POWER EFFICIENCY

(VARIABLE SWITCHING FREQUENCY)

100

BATT = 5.5V

90

SYNC = REF
IDLE = 1

80

MODE1 = 1
MODE0 = 0

70
60
50
40

POWER EFFICIENCY (%)

30
20

10

100

90
80

70
60

50
40

POWER EFFICIENCY (%)

30
20

10

%

1 10 100 1000

3OUT OUTPUT CURRENT (mA)

3OUT OPERATE MODE POWER EFFICIENCY

(FIXED 230kHz SWITCHING FREQUENCY)

BATT = 7.5V
SYNC = AGND
IDLE = 0
MODE1 = 1
MODE0 = 0

1 10 100 1000

3OUT OUTPUT CURRENT (mA)

3OUT OPERATE MODE POWER EFFICIENCY

(VARIABLE SWITCHING FREQUENCY)

450
400

MAX781-12

350
300
250

kHz

200
150
100
50

0

MAX781-07

100

BATT = 5.5V

90

SYNC = AGND
IDLE = 1

80

MODE1 = 1
MODE0 = 0

70
60
50
40

POWER EFFICIENCY (%)

30

SWITCHING FREQUENCY (kHz)

20
10

100

90
80
70
60
50
40

POWER EFFICIENCY (%)

30
20

10

%

1 10 100 1000

3OUT OUTPUT CURRENT (mA)

3OUT OPERATE MODE POWER EFFICIENCY

(VARIABLE SWITCHING FREQUENCY)

BATT = 7.5V
SYNC = REF
IDLE = 1
MODE1 = 1
MODE0 = 0

%

1 10 100 1000

3OUT OUTPUT CURRENT (mA)

kHz

450
400

MAX781-10

350
300
250
200

kHz

150
100

SWITCHING FREQUENCY (kHz)

50
0

450
400

MAX781-11

350
300
250
200
150
100

SWITCHING FREQUENCY (kHz)

50
0

6 _______________________________________________________________________________________

PDA/Hand-Held Computer Power Controller

____________________________Typical Operating Characteristics (continued)

(TA = +25°C, unless otherwise noted.)

3OUT OPERATE MODE POWER EFFICIENCY

VARIABLE SWITCHING FREQUENCY

100

BATT = 7.5V

90

SYNC = AGND
IDLE = 1

80

MODE1 = 1
MODE0 = 0

70
60
50
40

POWER EFFICIENCY (%)

30
20

10

%

1 10 100 1000

3OUT OUTPUT CURRENT (mA)

kHz

450
400

MAX781-09

350
300
250
200
150
100

SWITCHING EFFICIENCY (kHz)
50
0

USING THE BATTERY CHARGER TO DRIVE

A CCFL BACKLIGHT ROYER OSCILLATOR

2.5
SYNC = REF

VCHG = 7V

2.0
BATT = VCHG - DIODE DROP

R4 = 0.47Ω

1.5

1.0

0.5

CCFL TUBE CURRENT (mA, rms)

0

0

mV

mA, rms

10 20 30 40 50 60 70

CHG6–CHG0 BITS VALUE

110
100

MAX781-01

90
80
70
60
50
40
30

CSBAT AVERAGE VOLTAGE (mV)

20
10

______________________________________________________________Pin Description

PIN

1–4 GD2–GD5 High-Side Gate-Driver Outputs

5 VPPA VPP-Programming Voltage Output A
6 VHI VPPA, VPPB Linear-Regulator Input Power
7 VPPB VPP-Programming Voltage Output B
8 AGND Analog Ground

9 SYNC Oscillator Frequency Control and Synchronization Input
10 CE Serial-Interface Chip-Enable Input—active high
11 SCLK Serial-Interface Clock Input
12 DOUT Serial-Interface Data Output
13 DIN Serial-Interface Data Input
14 INT Interrupt Output
15 FAST General-purpose open-drain output
16 COMP Battery-Charger Compensation
17 CSBAT Battery-Charger Current-Sense Input
18 5OUT Linear-Regulated +5V Output
19 DCHG Battery-Charger MOSFET Gate-Driver Output
20 PGND Power Ground
21 DLO +3.3V Regulator, Synchronous Rectifier, Gate-Driver Output
22 BST +3.3V Regulator Boost Capacitor Connection (0.1µF to LX)
23 DHI +3.3V Regulator High-Side Gate-Driver Output
24 LX +3.3V Regulator Inductor Connection

NAME FUNCTION

MAX781

_______________________________________________________________________________________

7

PDA/Hand-Held Computer Power Controller

_________________________________________________Pin Description (continued)

25 3OUT +3.3V Regulator Feedback Connection and Linear-Regulated + 3.3V Output
26 CS +3.3V Regulator Current-Sense Input
27 SS +3.3V Regulator Soft-Start Capacitor Connection
28 BATT Battery Voltage Input
29 VCHG Charger Voltage Input

MAX781

30 UVLO Undervoltage Lockout Threshold Input
31 REF +2.5V Reference Output
32 AOUT Analog Multiplexer Buffered Output
33 TEMP Analog Multiplexer Input and Battery Sense Input
34 AUXIN Analog Multiplexer Input
35
36 GD1 High-Side Gate-Driver Output

BATTERY
CHARGER
DC INPUT

C10

–S—H—D—N–

D3

R4

Shutdown-Mode Control Input

C14 D1

L1

R8

T

D2

COMPATIBLE

INTERFACE

M3

SPI

SERIAL 

R1

C1

BATTERY
CHARGER
SECTION

C3 C2

VCHG

DCHG

REF
SYNC
TEMP

COMP

CSBAT

CE
SCLK
DIN
DOUT
INT

FAST
AUXIN
AOUT

SHDN

MAX781

UVLO SS

C5

5OUT

BATT

BST

DLO

PGND

3OUT

AGND

VPPA
VPPB

GD1

GD5

VHI

DHI

+5V LOW 
CURRENT OUTPUT


C12

D7

M1

C7

LX

M2

CS

GATE DRIVERS
FOR POWER
SWITCHING

D6

T1

D5

C8

C11

R7

C9

+14V OUTPUT

PCMCIA 2.0
CARD SLOT
VPPs

C6

+3.3V
OUTPUT

Figure 1. Typical Operating Circuit

8 _______________________________________________________________________________________