ADP1649ACBZ-R7 datasheet(14/28 Pages) AD

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ADP1649

Data Sheet

Rev. 0 | Page 14 of 28

Table 8. VDD Level at Which the VBAT Low Function Is Enabled

Bit Name

DD Level

V_VB_LO

000 = disabled (default)

001 = 3.3 V

010 = 3.35 V

011 = 3.4 V

100 = 3.45 V

101 = 3.5 V

110 = 3.55 V

111 = 3.6 V

PROGRAMMABLE BATTERY DC CURRENT LIMIT

The ADP1649 has four optional programmable input dc current

limits that limit the maximum input battery current over all con-

ditions. This allows use of higher LED currents in a system with

significant variation in LED forward voltage (VF) and supply

battery voltage without risk of exceeding the current allocated

to the flash.

Table 9. Input DC Current Limit Setting the LED Current

Bit Name

Current Limit

IL_DC

00 = 1.5 A

01 = 1.75 A

10 = 2.0 A (default)

11 = reserved

During startup of the flash, if the battery current does not reach

the dc current limit, the LED current is set to the current value

of the I_FL bits. If the battery current reaches the programmed

dc current limit on startup, the LED current does not increase

further. The dc current limit flag is set in the fault information

reduced current-limit LED current and are available for readback.

Figure 32. DC Current-Limit Operation in a Low Battery, High LED VF Case

The camera system shown in Figure 33 can adjust the image

sensor settings based on the known reduced LED current for a

low battery and a high VF LED.

Figure 33. Use of the DC Current Limit in an Optimized Camera System

REG 0x02, FL_TIM = XXXX ms

REG 0x03, I_FL = XXXXX mA

REG 0x07 IL_DC_EN = 1

REG 0x07 IL_DC = XX A

I2C DATA BUS

STROBE

ADP1649 SETS OUTPUT_EN TO 0.

ADP1649 SETS LED_MOD TO 00.

NO LIMIT LED CURRENT

ACTUAL LED CURRENT

ADP1649 SETS FL_IDC (REG 0x05) TO 1.

ADP1649 SETS I_FL TO ACTUAL LED CURRENT.

REG 0x04, OUTPUT_EN = 1

STR_LV = 1

LED_MOD = 11

SELECT FLASH CURRENT

SELECT MAX BATTERY CURRENT

PREFLASH STROBE

DC LIMIT HIT?

LED CURRENT =

PROGAMMED LED

CURRENT

LED CURRENT =

REDUCED LED CURRENT

YES

BATTERY CURRENT =

PROGRAMMED DC LIMIT

I2C READ LED CURRENT

ADJUST IMAGE SENSOR

STROBE

ADP1649ACBZ-R7 数据表(PDF) 14 Page - Analog Devices

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