ADM8845EB-EVALZ Analog Devices Inc, ADM8845EB-EVALZ Datasheet - Page 16

• Manufacturer Part Number: ADM8845EB-EVALZ
• Description: BOARD EVALUATION FOR ADM8845
• Manufacturer: Analog Devices Inc

Specifications of ADM8845EB-EVALZ

• Current - Output / Channel: 20mA
• Outputs And Type: 6, Non-Isolated
• Voltage - Output: 5.5 V
• Features: Charge Pump, Dimmable
• Voltage - Input: 2.6 ~ 5.5V
• Utilized Ic / Part: ADM8845
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ADM8845
DRIVING FOUR BACKLIGHT WHITE LEDs AND
FLASH LEDs
The ADM8845 can be configured to power four backlight white
LEDs and a camera flash, bundled into one package. FB1 to FB4
power the backlight light, FB5 and FB6 power two of the flash
LEDs, while the third is powered by an external current mirror
to control the current flowing through the third flash LED (see
Figure 33). All the backlight white LEDs have 15 mA/LED, and
the flash current is 20 mA/LED. The total load on the
ADM8845 charge pump is 120 mA; the maximum load on
the ADM8845 charge pump is 180 mA (see Figure 21).
7.32kΩ
4.7µF
R
SET
C4
CTRL2
CTRL1
V
I
CC
SET
ADM8845
CONTROL
CONTROL
CURRENT
CIRCUIT
LOGIC
LED
V
1×/1.5×/2× MODE
CHARGE PUMP
REF
1µF
C1
CURRENT CONTROLLED SINKS
OSC
1µF
C2
GND
Figure 33. Driving Four Backlight LEDs and Flash LED
Rev. C | Page 16 of 20
V
FB1
FB2
FB3
FB4
FB5
FB6
CTRL1 controls the flash on/off, and CTRL2 controls the back-
light on/off and brightness control. Because the R
the current that each of the six current control blocks can sink,
a PWM signal is used to change the current in the backlight
from 20 mA to 5 mA/LED. The CTRL2 duty cycle is 15/20 to
give 15 mA/backlight LED.
OUT
C3
2.2µF
15mA/LED
BACK-
LIGHT
R
20mA/LED
FLASH
CURRENT
CONTROL 7
SET
resistor sets