RT9451 datasheet(28/37 Pages) RICHTEK

28 / 37 page

RT9451

DS9451-00

September 2013

www.richtek.com

is a registered trademark of Richtek Technology Corporation.

Charge Mode Operation

Minimum Input Voltage Regulation (MIVR)

The RT9451 features input voltage MIVR function to prevent

input voltage drop due to insufficient current provided by

the adaptor or USB input. If MIVR function is enabled, the

input voltage decreases when the over current of the input

power source occurs and is regulated at a predetermined

voltage level which can be set from 4.20V to 4.76V with

the step of 80mV by I2C interface to MIVR [2:0] in the

the host and the CHMIVR bit is set to high. At this time,

the current drawn by the RT9451 equals to the maximum

current value that the input power can provide at the

predetermined voltage level, instead of the set value. And

CHMIVR bit is set to

“1” and INT pin is pulled low to

notify the host. The MIVR function is initially set to 4.36V.

Figure 1

USB Power Source Detection (DPDM Detection)

An USB charger detection mechanism is integrated in

RT9451 to detect between dedicated charger or not. The

detection is triggered by VIN power on or DPDN_EN bit in

the register address of 0x00h. The DPDN_EN bit is

automatically reset to

“0” after it is triggered. The DPDM

detection status and result are reported in DPDM_D

DPDM_R bits in the register address of 0x07h. The result

is set to 975mA for dedicated charger (DP and DM pins

short together) or 500mA for others. The detection

mechanism can be disable by pulling VIO pin high.

Active Input Current Regulation (AICR)

The AICR setting is determined by both AICR [1:0] in

bit in register 0x01h. If LMTSEL bit is set to

“0”, the valid

current limit is the maximum value of AICR [1:0] and

DPDM_R result. If LMTSEL bit is set to

“1”, the AICR

[1:0] dominates and DPDM_R result is ignored. For the

latter, the input current limit of

“00”, “01” and “10” in

AICR [1:0] corresponds to 100mA, 500mA and 975mA

respectively. If the application does not need input current

limit, write

“11” into the AICR [1:0].

Charge Profile

The RT9451 provides a precision Li-ion or Li-polymer

charging solution for single-cell applications. Input current

limit, charge current, termination current, charge voltage

and input voltage MIVR are all programmable via the I2C

interface. In charge mode, the RT9451 has five control

loops to regulate input current, charge current, charge

voltage, input voltage MIVR and device junction

temperature. During the charging process, all five loops

are enabled and the dominant one will take over the control.

For normal charging process, the Li-ion or Li-polymer

battery is charged in three charging modes depending on

the battery voltage. At the beginning of the charging

process, the RT9451 is in pre-charge mode. When the

battery voltage rises above pre-charge threshold voltage

(VPREC), the RT9451 enters fast-charge mode. Once the

battery voltage is close to the regulation voltage (VOREG),

the RT9451 enters constant voltage mode.

Pre-Charge Mode

For life-cycle consideration, the battery can not be charged

with large current under low battery condition. When the

BATS pin voltage is below pre-charge threshold voltage

(VPREC), the charger is in pre-charge mode with a weak

charge current which equals to the pre-charge current

(IPREC). In pre-charge mode, the charger basically works

as an LDO. The pre-charge current also acts as the current

limit when the BATS pin is shorted.

VIN

IIN

Expected IIN

VIN MIVR

Final IIN

set charge current

RT9451 数据表(PDF) 28 Page - Richtek Technology Corporation

RT9451 数据表(HTML) 28 Page - Richtek Technology Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37

数据表下载