ADM8845ACPZ-REEL Analog Devices Inc, ADM8845ACPZ-REEL Datasheet - Page 17

• Manufacturer Part Number: ADM8845ACPZ-REEL
• Description: IC,Laser Diode/LED Driver,LLCC,16PIN,PLASTIC
• Manufacturer: Analog Devices Inc
• Type: Backlight, White LEDr

Specifications of ADM8845ACPZ-REEL

• Constant Current: Yes
• Topology: PWM, Switched Capacitor (Charge Pump)
• Number Of Outputs: 6
• Internal Driver: Yes
• Type - Primary: Backlight, Flash/Torch
• Type - Secondary: White LED
• Frequency: 200kHz
• Voltage - Supply: 2.6 V ~ 5.5 V
• Voltage - Output: 4.81V
• Mounting Type: Surface Mount
• Package / Case: 16-LFCSP
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: 30mA
• Internal Switch(s): Yes
• Efficiency: 88%
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: ADM8845EB-EVALZ - BOARD EVALUATION FOR ADM8845
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

POWER EFFICIENCY
The ADM8845 power efficiency (η) equations are
where:
I
V
Gain is equal to the charge pump mode (1
3.4V
Examples 1 and 2 show calculations of the ADM8845 power
efficiency. See Figure 34 as well.
Q
F
R
is the quiescent current of the ADM8845, 2.6 mA.
is the LED forward voltage.
SET
V
η = P
P
P
I
IN
CC
IN
OUT
= ((V
= 6 × (V
OUT
V
CTRL1
CTRL2
I
SET
Figure 34. Charge Pump Power Efficiency Diagram
CC
/P
CC
ADM8845
IN
× I
GND
F
LOAD
× I
LED
V
× Gain) + (I
FB1
FB2
FB3
FB4
FB5
FB6
OUT
)
I
LOAD
Q
× V
CC
×
))
, 1.5
×
, 2
×
).
Rev. C | Page 17 of 20
Example 1
The ADM8845 driving six white LED with 20 mA/LED at
V
P
P
P
P
P
P
P
η = P
η = 0.54/0.62084
η = 87%
Example 2
The ADM8845 driving six white LED with 20 mA/LED at
V
P
P
P
P
P
P
P
η = P
η = 0.432/0.62084
η = 70%
IN
IN
IN
IN
OUT
OUT
OUT
IN
IN
IN
IN
OUT
OUT
OUT
CC
CC
= ((V
= ((3.4 × 120 mA × 1.5) + (3.4 × 2.6 mA))
= ((0.612) + (0.00884))
= 0.62084
= ((V
= ((3.4 × 120 mA × 1.5) + (3.4 × 2.6 mA))
= ((0.612) + (0.00884))
= 0.62084
= 3.4 V (1.5× mode), LED V
= 3.4 (1.5× mode), LED V
= 6 × (V
= 6 × (4.5V × 20 mA)
= 0.54
= 6 × (V
= 6 × (3.6 V × 20 mA)
= 0.432
OUT
OUT
/P
/P
CC
CC
IN
IN
× I
× I
F
F
LOAD
LOAD
× I
× I
LED
LED
× Gain) + (V
× Gain) + (V
)
)
F
CC
CC
= 3.6 V.
F
× I
× I
= 4.5 V.
Q
Q
))
))
ADM8845