ADP1650ACPZ-R7 datasheet(15/32 Pages) AD

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ADP1650

Rev. C | Page 15 of 32

PROGRAMMABLE BATTERY DC CURRENT LIMIT

The ADP1650 has four optional programmable input dc current

limits that limit the maximum battery current that can be taken

over all conditions. This allows higher LED currents to be used

in a system with significant variation in LED forward voltage

(VF) and supply battery voltage without risk of the current

allocated to the flash being exceeded.

Table 8. 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 = 2.25 A

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 does hit 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

current and are available for readback.

REG 0x02, FL_TIM = XXXX ms

REG 0x03, I_FL = XXXXX mA

IL_DC_EN = 1

IL_DC = XX A

I2C DATA BUS

STROBE

ADP1650 SETS OUTPUT_EN TO 0.

ADP1650 SETS LED_MOD TO 00.

NO LIMIT LED CURRENT

ACTUAL LED CURRENT

ADP1650 SETS FL_IDC (REG 0x05) TO 1.

ADP1650 SETS I_FL TO ACTUAL LED CURRENT.

REG 0x04, OUTPUT_EN = 1

STR_LV = 1

LED_MOD = 11

Figure 35. DC Current Limit Operation in a Low Battery, High LED VF Case

The camera system shown in Figure 36 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 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

Figure 36. Use of the DC Current Limit in an Optimized Camera System

ANALOG-TO-DIGITAL CONVERTER OPERATION

The internal 4-bit analog-to-digital converter (ADC) is configura-

ble to measure the LED VF, integrated circuit (IC) die temperature,

or an external voltage using the GPIO2 pin. Read the 4-bit

resolution output code back from Register 0x08 using the I2C

interface.

INTERFACE/

CONTROL

LED_OUT

SDA

SCL

ADC_EN[1:0]

4-BIT ADC

IC TEMPERATURE

SENSOR

GPIO2

ADC_VAL[5:2]

PTC

Figure 37. Available ADC Modes in the ADP1650

The ADC can perform the conversion either immediately on an

I2C command, or it can delay the conversion until the next time

the ADP1650 exits an active mode. Delayed conversion can be

useful, for example, for measuring the IC temperature at the

end of a timed flash period. To set up a delayed conversion, set

ADC_EN to the required mode while OUTPUT_EN = 0. Then

set the ADP1650 to the desired output mode (torch, flash assist

light, or 5 V output) and set OUTPUT_EN = 1. The ADC conver-

sion is performed when the ADP1650 exits the chosen mode.

To perform an immediate conversion, set ADC_EN to the

required mode during ADP1650 operation (OUTPUT_EN = 1).

Note that an ADC conversion cannot be performed when the

ADP1650 is idle. This is interpreted as an attempt to set up a

delayed conversion.

LED VF Mode

The ADC can measure the LED VF in both flash and assist/

torch modes. In torch mode, set ADC_EN = 01 to begin a

conversion. The value can be read back from the ADC_VAL[5:2]

bits 1 ms after the conversion has started. Assist/torch mode,

rather than flash mode, is best in the handset production test to

verify the LED VF.

REG 0x08, ADC_EN = 01

START CONVERSION

(INTERNAL SIGNAL)

1ms

ADC_VAL[5:2]

AVAILABLE FOR READ

I2C DATA BUS

Figure 38. ADC Timing for All Modes Except VF Measurement in Flash Mode

In flash mode, set ADC_EN = 01. The conversion happens just

before the timeout occurs; therefore, the FL_TIM bits set when

the ADC sample occurs. This allows the VF to settle from the

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