Datasheet

ADP1660 Data Sheet
Rev. 0 | Page 10 of 28
THEORY OF OPERATION
The ADP1660 is a high power, I
2
C programmable, dual white
LED driver ideal for driving white LEDs for use as a camera
flash. The ADP1660 includes a boost converter and two current
regulators suitable for powering two high power white LEDs.
WHITE LED DRIVER
The ADP1660 drives a synchronous 3 MHz boost converter as
required to power the high power LEDs.
• If the sum of the LED forward voltage plus the current
source headroom voltage is higher than the battery voltage,
the boost converter is turned on.
• If the battery voltage is higher than the sum of the LED
forward voltage plus 2× the current source headroom
voltage, the boost converter is disabled and the part
operates in pass-through mode.
The ADP1660 uses an integrated P-FET high-side current
regulator for accurate brightness control.
The ADP1660 supports the setting of different currents for each
LED, although this configuration is not recommended. Any mis-
match in the forward voltage of the two LEDs translates directly
to lower efficiency, as well as lower accuracy of the current for the
lower voltage LED. It is recommended that the voltages on the two
LEDs be kept within 1 V of one another during operation. The
user can disable one LED and use the other LED only, if desired.
MODES OF OPERATION
When the enable pin is high, the I
2
C-compatible interface can
be used to set the ADP1660 to one of seven modes of operation.
These modes are configured using the LED_MOD bits (Bits[2:0])
in Register 0x01 (see Table 7).
Table 7. Modes of Operation Set by the LED_MOD Bits
LED_MOD Bits Operating Mode
000
Standby mode, consuming 3 µA typical
(default)
001 Fixed 5 V output mode
010 Assist light mode with continuous LED current
011
Flash mode with LED currents up to 750 mA
available for up to 1.6 sec
100
Independent trigger mode with timeout
enabled (LED outputs are disabled if they are
on longer than the timer value configured by
the FL_TIM bits)
101
Independent trigger mode with timeout
disabled (FL_TIM value is ignored)
110
Fixed 5 V output mode with torch mode (total
output current must be below 500 mA)
111 Reserved
PWM
CONTROLLER
PGND
PGND
VOUT
SW
PGNDSGND
VIN
UVLO
OVP
FAULT
REGISTER
IC THERMAL
SENSING
HP LED
SHORT
HP LED
DRIVER
CURRENT
SENSE
CURRENT
SENSE
SCL
STROBE
PGND
PGNDAGND
C
OUT
10µF
L1
1µF
INPUT VOLTAGE =
2.7V TO 5.0V
C
IN
10µF
GPIO
SDA
TORCH
EN
5.5V
CURRENT
SENSE
HP LED
DRIVER
HIGH POWER LED
CURRENT CONTROL
LED2
UP TO
750mA
PGND
UP TO
750mA
INTERFACE
AND
CONTROL
TORCH TxMASK
IO_CFG
2.4V
11018-011
LED1
Figure 16. Detailed Block Diagram