RT9945

21

DS9945-01 April 2011

www.richtek.com

If a power good fault is not present at the end of the power good check mode and then NORMAL mode starts. In this mode

the handheld device. The following pins and battery voltages determine the power on/off status of the handset :

PWR_ON

PWR_HOLD

Logic high on PWR_ON pin is the normal way of powering up a handset. The PWR_ON signal is held high for at least 320

ms; Buck1, 2 and LDO1, 3 are turned on; when Buck2 reaches 87% of its final value, a 200ms reset timer is started at

after which nRESET is asserted high, and then the handheld device processor is initialized and will assert PWR_HOLD

high to maintain power on. This wrap around constitutes the PWR_ON button can be released (return to low state) and the

power remains on. If, however, PWR_ON is released before the PWR_HOLD signal is asserted, then Buck1, 2 and LDO1,

3 will be turned off. All output could be turned off by the processor asserting PWR_HOLD low, if PWR_ON = Low.

The RT9945's default power output voltages for Samsung platform are listed in Table 4 as following :

Figure 6. Power and Interface Module

I

Decoder

I

Registers

and Non-

Volatile

Memory

Interrupt

Controller

System and

Battery

Charger

Control Logic

Sequencing

& Operating

Mode

Setting

Host

Processor

CLK

DATA

nINT

nRESET

nPBSTAS

PWR_HOLD

HP_PWR

PWR_ON

VSYS

VMEM

VSYS

PWR_IN

BATT

PWR_EN

VSYS

VSYS

Table 4. The RT9945 for Samsung Platform Power Terminology

Buck1

Buck 2

LDO1

LDO2

LDO3

LDO4

LDO5

Control Pin

PW R_ON

PW R_EN

PWR_ON

PWR_EN

PWR_ON

I

Default Output

Voltage

1.8V

1.35V

3.3V

1.2V

1.2V

2.5V

3.3V

LDO1, 2 voltage setting by Pin S1 and S2

LDO2 and Buck2 can be turned on by PWR_EN pin.

Sleep Mode

The external host can set the RT9945 in sleep mode using the GPIO configuration. In the sleep mode, change the

PWR_EN signal to set different output on/off status :

1. Buck2 and LDO2 will be disabled when the PWR_EN is turned off to enter the sleep mode.

2. When the PWR_EN is turned on, the Buck2 and LDO2 are enabled and the reset signal from the RT9945 remains high.