MAX781CBX 데이터 시트보기 (PDF) - Maxim Integrated

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MAX781CBX

PDA/Hand-Held Computer Power Controller

Maxim Integrated 

PDA/Hand-Held Computer Power Controller

_______________Detailed Description

Modes of Operation

Table 1 describes the MAX781’s four modes of opera-

tion, 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 1. MAX781 Modes of Operation

MODE

DESCRIPTION

Shutdown

• Entire chip shut down

• All blocks turned off

• IQ < 10µA

• 3OUT, 5OUT, REF off

Low

Power

• 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)

Standby

• 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

Operate • VHI regulated to +14V

• Analog multiplexer enabled

• High-side gate drivers enabled

• Battery-charging current source enabled

With –S—H—D—N– pulled up to the battery voltage, the

MAX781 powers on in low-power mode. After power-

up, 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.

Table 2. Operating Modes

–S—H—D—N– MODE1 MODE0 CE

0

x

x

x

1

1

1

1

1

1

1

0

1

0

1

1

1

0

1

0

1

0

0

x

1

1

0

x

Resulting Mode

Shutdown

Operate

Low Power (default

on power-up)

Standby

Low Power

Standby

Operate

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 require-

ments 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.

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 sta-

tus. It is assumed that the battery pack used with the

MAX781 has a thermistor attached to its negative termi-

10 ______________________________________________________________________________________

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