Triple-Output Power-Supply

Controller for Notebook Computers

8

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_________________________________________________Pin Description (continued)

PIN

NAME

FUNCTION

DH3

BST5

+5V-supply boost capacitor connection (0.1µF to LX5)

+3.3V-supply external MOSFET high-side switch-drive output

DL5

+5V-supply external MOSFET synchronous-rectifier drive output

33

PGND

Power ground

FB3

24

25

+3.3V-supply feedback and low-side current-sense terminal

FB5

+5V-supply feedback input and low-side current-sense terminal

34

VL

Internal 5V-supply output. Bypass with 4.7µF. This pin is linearly regulated from V+ or switched to the

+5V output to improve efficiency. VL is always on and can source up to 5mA for external loads.

V+

Main (battery) input: 5.5V to 30V

DL3

+3.3V-supply external MOSFET synchronous-rectifier drive output

26

27

28

BST3

+3.3V-supply boost capacitor connection (0.1µF to LX3)

LX3

+3.3V-supply inductor connection

29

30

31

32

SS3

+3.3V-supply soft-start control input. Ramp time to full current limit is 1ms/nF of capacitance to GND.

36

CS3

+3.3V-supply current-sense input. Maximum is +100mV referenced to FB3.

35

Table 1. Truth Table for VPP Control Pins

D_0

D_1

VPP_

0

0

1

1

0

1

0

1

0V

5V

12V

Hi-Z

_______________Detailed Description

The MAX782 converts a 5.5V to 30V input to five outputs

(Figure 1). It produces two high-power, switch-mode,

pulse-width modulated (PWM) supplies, one at +5V and

the other at +3.3V. These two supplies operate at either

200kHz or 300kHz, allowing extremely small external

components to be used. Output current capability

depends on external components, and can exceed 5A

on each supply. A 15V high-side (VDD) supply is also

provided, delivering an output current that can exceed

300mA, depending on the external components chosen.

Two linear regulators supplied by the 15V VDD line cre-

ate programmable VPP supplies for PCMCIA slots.

These supplies (VPPA, VPPB) can be programmed to be

grounded or high impedance, or to deliver 5V or 12V at

up to 60mA.

An internal 5V, 25mA supply (VL) and a 3.3V, 5mA ref-

erence voltage (REF) are also generated, as shown in

Figure 2. Fault-protection circuitry shuts off the PWM

and high-side supply when the internal supplies lose

regulation.

Three precision comparators are included. Their out-

put stages permit them to be used as level translators

for driving high-side external power MOSFETs: For

example, to facilitate switching VCC lines to PCMCIA

slots.