ADP1649ACBZ-R7 datasheet(15/28 Pages) AD

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Data Sheet

ADP1649

Rev. 0 | Page 15 of 28

ANALOG-TO-DIGITAL CONVERTER OPERATION

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

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

temperature, or to measure an external voltage using the GPIO2

pin. Read the 4-bit resolution output code from Register 0x08

using the I2C interface.

Figure 34. Available ADC Modes

The ADC can perform the conversion immediately on an I2C

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

ADP1649 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. Next, set the ADP1649 to the

desired output mode (torch, flash assist light, or 5 V output) and

set OUTPUT_EN = 1. The ADC conversion is performed when

the ADP1649 exits the chosen mode.

To perform an immediate conversion, set ADC_EN to the

required mode during ADP1649 operation (OUTPUT_EN = 1).

Note that an ADC conversion cannot be performed when the

ADP1649 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.

Figure 35. ADC Timing for All Modes Except VF Measurement in Flash Mode

In flash mode, set ADC_EN = 01. The conversion occurs imme-

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

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

initial peak as the junction temperature of the LED stabilizes.

An LED temperature vs. flash time profile for the handset PCB

design can be generated during the design phase by varying the

FL_TIM bits from the lowest to the highest setting and collecting a

VF sample on each flash.

Figure 36. ADC Timing for VF Measurement in Flash Mode

Die Temperature Mode

The ADC measures the IC die temperature and provides the result

to the I2C interface. This is useful during the design phase of the

flash system to optimize PCB layout for the best thermal design.

Write ADC_EN = 10 to begin a die temperature measurement.

The value can be read back from the ADC_VAL[5:2] bits 1 ms

after the conversion has started. The most stable and accurate value

of the die temperature is available at the end of the flash pulse.

External Voltage Mode

The ADC measures the voltage on the GPIO2 pin when the GPIO2

is configured as an ADC input by setting IO2_CFG = 11. One

example is using an external temperature dependent resistor to

create a voltage based on the temperature of the flash LED. The

EN line can be used for biasing to reduce leakage current when

the flash is not being used.

5 V OUTPUT OPERATION

The ADP1649 can be used as a 5 V boost to supply up to 500 mA

for an audio voltage rail or keypad LED driver voltage. To move

into voltage regulation mode, the OUTPUT_EN bit must be set

to 0. To enable the 5 V output, set LED_MOD[1:0] = 01, and set

OUTPUT_EN = 1. The ADP1649 sets the VOUT pin to 5 V

and disconnects VOUT from LED_OUT. The VOUT pin is

connected to the SW node when the ADP1649 is not enabled.

Do not connect VOUT directly to a positive external voltage

source because this causes current to flow from VOUT to the

battery.

INTERFACE/

CONTROL

LED_OUT

SDA

SCL

ADC_EN[1:0]

4-BIT ADC

IC TEMPERATURE

SENSOR

GPIO2

ADC_VAL[5:2]

PTC

REG 0x08, ADC_EN = 01

START CONVERSION

(INTERNAL SIGNAL)

1ms

ADC_VAL[5:2]

AVAILABLE FOR READ

I2C DATA BUS

LED CURRENT

REG 0x02, FL_TIM = XXXX ms

REG 0x03, I_FL = XXXXX mA

REG 0x04, OUTPUT_EN = 1

STR_LV = 0

LED_MOD = 11

I2C DATA BUS

STROBE

FL_TIM

START CONVERSION

(INTERNAL SIGNAL)

ADC_VAL[5:2]

AVAILABLE FOR READ

REG 0x08, ADC_EN = 01

tS = 1ms

IFLASH

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