RT9481 datasheet(20/41 Pages) RICHTEK

20 / 41 page

RT9481

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

DS9481-00 June 2015

Boost Mode Flow

The Boost mode could start from device attached, and

the flag of USBOUT_STAI (MISC_STA2[4]) will be set

to high for indicate the device attached. The USBOUT

attach detection is control by register ATTACH_CTL[5].

If there is no any Boost fault triggered in registers

CHG_STAT2 or BST_IRQ or MISC_IRQ, the host can

decide to turn on Boost or not. The host can set user

Boost setting before turn on the Boost from registers

CHG_CTRL1 to CHG_CTRL6 and please refer to I2C

The Boost could be enable by set OPA_MODE

(CHG_CTRL1[0]) to high and setting SWITCHING_EN

(CHG_STA1[0]) to high.

Before enable the Load Switch suggest to wait Boost

soft start (CHG_IRQ[3]) finish, it can guarantee the

Boost ready for output.

Then the host could set EN_LDSW (USBOUT_CTL[6])

to high to turn on Load Switch and the Boost would

start output current to device. For let device identify the

power bank is a powerful adapter, to set EN_DCP

(USBOUT_CTL[7]) to high to turn on DCP controller at

the same time.

USBOUT light load detection (USBOUTLD_CTL[5:3])

can help the host to check the device charging full or

device detached by the condition of USBOUT current

is under the threshold or not. But according to USB

standard, the device will start charging after it connect

to adapter 100 millisecond. We suggest to add delay

time tULD over 100 millisecond before enable USBOUT

light load detection after Load Switch turn on. It could

avoid USBOUT light load detection trigger early.

The host could read BOOST_STAT (CHG_STA1) to

make sure the Boost is in progress.

Discharging Terminate

There are two conditions to terminate discharging.

Boost Fault

The Boost automatically terminates when Boost fault

event be triggered in Table 8.

Table 8. Boost Fault Event

Boost Fault

Event

Flag

Thermal

Shutdown

TSD_STAT

CHG_STA2[2]

Boost Thermal

Shutdown

BSTTSDI

BST_IRQ[7]

VMID Over

Voltage Protect

BSTVMIDVPI

BST_IRQ[6]

Battery Voltage

is too Low

BSTLOWVI

BST_IRQ[5]

Load Switch

Short Current

Protect

LDSW_SCPI

MISC_IRQ[5]

VMID Short

Current Protect

VMIDSCPI

MISC_IRQ[1]

VMID Under

Voltage Protect

VMIDUVPI

MISC_IRQ[0]

USBOUT Light Load

It means device charging full or device detached when

USBOUTLD_STAT (MISC_STA2) set to high. According

to USBOUTLD_STAT, the host could decide to turn off

Boost or not.

Set ADC Channel

CH_SEL (ADC_CLT[7:5])

and

Start ADC Conversion

ADC_START (ADC_CLT[0]) = 1

ADC Conversion Starts

Finish ADC Conversion

Check ADC Conversion Complete

ADC_DONEI (MISC_IRQ[7]) = 1

ADC_STAT (MISC_STAT1) = 0

Read ADC Code

ADC_CODEH[7:0]、

ADC_CODEL[7:0]

and

Calculate measurement

Figure 4. ADC Conversion Operation Flow

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