ADP1660ACBZ-R7 datasheet(14/28 Pages) AD

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ADP1660

Data Sheet

Rev. 0 | Page 14 of 28

BATTERY INPUT DC CURRENT LIMIT

The ADP1660 has an optional programmable input dc current

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

ditions. This feature allows higher LED currents to be used in a

system with significant variation in LED forward voltage (VF) and

supply battery voltage without the risk of exceeding the current

allocated to the flash. To enable the input dc current limit, set

the IL_DC_EN bit (Bit 0) in Register 0x03. To set the input dc

current limit, use the IL_DC bits (Bits[3:1]) in Register 0x03

(see Table 10).

Table 10. Input DC Current Limit

IL_DC Bit Value

DC Current Limit (A)

000

1.0

001

1.25

010

1.5

011

1.75

100

2.0 (default)

101

2.25

110

2.5

111

2.75

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

exceed the dc current limit, the LED1 and LED2 currents are

set to the values of the I_FL1 and I_FL2 bits in Register 0x06

and Register 0x09, respectively.

If the battery current exceeds 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 register (Bit 0

of Register 0x0C). The FL_I_FL1 bits in Register 0x0D and the

FL_I_FL2 bits in Register 0x0E are set to the actual LED current

values and are available for readback.

REG 0x02, FL_TIM = XXXXms

REG 0x06, I_FL1 = XX XXXXmA

REG 0x09, I_FL2 = XX XXXXmA

REG 0x03, IL_DC_EN = 1

IL_DC = XX A

I2C DATA BUS

STROBE

PROGRAMMED LED CURRENT

ACTUAL LED CURRENT

ADP1660 SETS FL_IDC (REG 0x0C) TO 1.

ADP1660 SETS FL_I_FL1 (REG 0x0D)

TO ACTUAL LED CURRENT.

ADP1660 SETS LED1_EN TO 0.

ADP1660 SETS LED2_EN TO 0.

ADP1660 SETS LED_MOD TO 000.

REG 0x0F, LED1_EN = 1

LED2_EN = 1

REG 0x01, STR_LV = 1

LED_MOD = 011

ADP1660 SETS FL_I_FL2 (REG 0x0E)

TO ACTUAL LED CURRENT.

Figure 25. DC Current Limit Operation in a Low Battery, High LED VF Case

The camera system shown in Figure 26 can adjust the image

sensor settings based on the known reduced LED current for

a low battery and a high VF LED.

SELECT FLASH CURRENT

SELECT MAX BATTERY CURRENT

PREFLASH STROBE

DC LIMIT

EXCEEDED?

LED CURRENT =

PROGRAMMED LED

CURRENT

LED CURRENT LOCKED

AT CURRENT VALUE

YES

BATTERY CURRENT =

PROGRAMMED DC LIMIT

READ LED CURRENT

(REG 0x0D AND REG 0x0E)

ADJUST IMAGE SENSOR

STROBE

Figure 26. Use of the DC Current Limit in an Optimized Camera System

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