lp5527tlx National Semiconductor Corporation, lp5527tlx Datasheet - Page 11

• 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

Flash Driver
LP5527 has an internal constant current driver that is ca-
pable for sinking low (50 mA) and high (400 mA) current
mainly targeted for torch and flash LED in camera phone
applications. 400 mA flash driver can be hardware or soft-
ware enabled. Flash safety function prevents hardware dam-
ages due to possible overheating when the flash has been
stuck on because of a hardware, software, or user error.
Flash LED Control (X = don’t care)
Flash Programming Example
FLASH DRIVER ELECTRICAL CHARACTERISTICS
Limits in standard typeface are for T
= 10 µF, C
= 1200Ω
Note 11: Flash turn-on time is measured from the moment the flash is activated until the flash current crosses 90% of its target value.
<
Address
00H
00H
00H
00H
Symbol
I
I
I
t
V
t
MAX
TORCH
LEAKAGE
FLASH
SAFETY
SAT
T
EN_TORCH bit
A
<
+85
X
0
1
OUT2
o
Data
8FH
9FH
FFH
BFH
C). Unless otherwise noted, specifications apply to the LP5527 Block Diagram with: V
Parameter
Maximum Sink Current
Torch Mode Sink Current 3.0V ≤ V
Flash Driver Leakage
Current
Flash Turn-On Time
(Note 11)
Saturation Voltage
Safety Time Accuracy
= 10 µF, C
Function
Sets safety time to 1.0s. In this example LED1 to LED4 are enabled.
Enables torch.
Activates FLASH. EN_FLASH bit and FLASH_SYNC bit are written simultaneously because EN_FLASH
disables torch.
Disables FLASH. If FLASH is disabled by safety time, FLASH_SYNC bit needs to be written to 0 before
next FLASH.
EN_FLASH bit
VDDIO
0
0
1
= 100 nF, C
J
= 25
Condition
3.0V ≤ V
V
3.0V ≤V
95% of the Maximum Sink Current
o
C. Limits in boldface type apply over the operating ambient temperature range (-30
FB
engage; from HIGH to LOW to
Change from LOW to HIGH to
VREF
= 5.0V
FLASH_SYNC bit or pin
IN
IN
IN
= 100 nF, C
≤ 5.5V, Current Decreased to
≤ 5.5V, V
≤ 5.5V
disengage
X
X
FLASH
VDDA
11
Flash safety counter starts counting when the flash is acti-
vated, and disables the flash automatically when the pre-
defined 1.0s or 2.0s time limit is reached. Flash is activated
with FLASH_SYNC bit or FLASH_SYNC pin, as defined in
the table below. Safety time limit is defined by SAFETY-
_TIME bit. (Time limit is 2.0s if SAFETY_TIME bit is low and
1.0s if the bit is high.)
= 4.7 µF, C
= 1.0V
VDD1
SAFETY_TIME bit
0 for 2.0 seconds;
1 for 1.0 second
= 100 nF, C
Min
370
(-7,5%)
-9
X
X
VDD2
Typ
400
50
0.1
20
550
IN
= 3.6V, C
= 100 nF, L
Max
430
(+7,5%)
+9
Flash LED Action
IN
Torch
Flash
= 10 µF, C
1
Off
= 4.7 µH, R
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Units
mA
mA
µA
µs
mV
%
OUT1
o
C
F