Datasheet

ADP1650
Rev. C | Page 16 of 32
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
V
F
sample on each flash.
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 die temperature is available at the end of the flash pulse.
External Voltage Mode
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
I
2
C DATA BUS
0A
I(FLASH)
STROBE
FL_TIM
START CONVERSION
(INTERNAL SIGNAL)
ADC_VAL[5:2]
AVAILABLE FOR READ
REG 0x08, ADC_EN = 01
t
S
= 1ms
08837-017
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 ADP1650 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 ADP1650 sets the VOUT pin to 5 V
and disconnects VOUT from LED_OUT. The VOUT pin is
connected to the SW node when the ADP1650 is not enabled.
VOUT should not be connected directly to a positive external
voltage source because this causes current to flow from VOUT
to the battery.
Figure 39. ADC Timing for V
F
Measurement in Flash Mode
Die Temperature Mode
The ADC measures the IC die temperature and provides the
result to the I
2
C interface. This is useful during the design phase
of the flash system to optimize PCB layout for the best thermal
design.
ADP1650
10µF
1.0µH
INPUT VOLTAGE
=
2.7V TO 5.0
V
PGND
SWSTROBE
10µF
LED_OUT
EN
SGND
SCL
SDA
GPIO1
GPIO2
OFF
ON
I
2
C BUS
SDA, SCL
EN
APPLICATIONS PROCESSOR
3.2 MEGAPIXEL
TO 5.0 MEGAPIXEL
CMOS IMAGE SENSOR
POWER-ON RESET
VOUT = 5.0V
KEYPAD
LED DRIVER
VDD
GND
VOUT*
VIN
08837-018
*THE VOUT PIN IS CONNECTED TO THE SW NODE WHEN THE ADP1650 IS NOT ENABLED. VOUT SHOULD NOT BE CONNECTED DIRECTLY TO A POSITIVE
EXTERNAL VOLTAGE SOURCE BECAUSE THIS WILL CAUSE CURRENT TO FLOW FROM VOUT TO THE BATTERY.
Figure 40. ADP1650 Voltage Regulation Mode: LED Driver Application