lp5527tlx National Semiconductor Corporation, lp5527tlx Datasheet - Page 12

• Manufacturer Part Number: lp5527tlx
• Description: Tiny Led Driver For Camera Flash And 4 Leds With I2c Programmability, Connectivity Test And Audio Synchronization
• Manufacturer: National Semiconductor Corporation

www.national.com
Constant Current Sink Outputs LED1, LED2, LED3, LED4
LP5527 has four independent backlight/keypad LED drivers.
All the drivers are regulated constant current sinks. LED
currents are controlled by 8-bit current mode DACs. Every
driver can be controlled in two ways:
1. Brightness control with constant current drivers
2. Direct ON/OFF control. The current is pre-set by 8-bit
In addition, LED1 driver can be synchronized to audio input
signal amplitude.
By using brightness control user can set brightness of every
single LED by using 8-bit brightness control registers. If
analog audio is available on system the user can use audio
synchronization for synchronizing LED1 to the music. Direct
ON/OFF control is mainly for switching LEDs on and off.
LED1 TO LED4 DRIVERS ELECTRICAL CHARACTERISTICS
Limits in standard typeface are for T
= 10 µF, C
9)
Note: Sink current matching is the maximum difference from the average.
<
Symbol
I
I
I
I
V
MAX
LEAKAGE
LED
MATCH
T
SAT
A
current mode DAC.
<
+85
OUT2
LED1[7:0], LED2[7:0] LED3[7:0], LED4[7:0] Register
o
C). Unless otherwise noted, specifications apply to the LP5527 Block Diagram with: V
= 10 µF, C
Parameter
Maximum Sink Current
Leakage Current
Current Tolerance
Sink Current Matching
Between LED 1 to 4
Saturation Voltage
VDDIO
= 100 nF, C
0000 0000
0000 0001
0000 0010
1110 0000
1111 1110
1111 1111
J
= 25
•
•
o
C. Limits in boldface type apply over the operating ambient temperature range (-30
Condition
V
I
I
3.0V ≤ V
to 95% of the Maximum Sink Current
VREF
SINK
SINK
FB
LED1 to LED4 Brightness Control
= 5.0V
=13.2 mA (target value)
=13.2 mA
= 100 nF, C
IN
≤ 5.5V, Current Decreased
VDDA
12
= 4.7 µF, C
LED Control Register (00 hex) has control bits for direct
on/off control of all the LEDs. Note that the LEDs have to be
turned on in order to control them with audio synchronization
(LED1 only) or brightness control.
The brightness is programmed as described in the following.
where:
n = LED[7:0] (8-bit)
step = 15 mA / 255 ≈ 0.05882 mA
For example if 13.2 mA is required for driver current:
n = 13.2 mA / (15 mA / 255) ≈ 224
224 = 1110 0000, E0 hex
VDD1
= 100 nF, C
Min
I
LED
Driver Current, mA (typical)
11.9
-10
= n x (15 mA / 255)
VDD2
Typical
IN
13.176
14.941
0.059
0.118
= 100 nF, L
0.03
13.2
150
15
= 3.6V, C
15
0
•
•
1
Max
IN
1
14.5
+10
230
= 4.7 µH. (Note
= 10 µF, C
Units
mA
mA
mV
µA
%
%
OUT1
o
C