參數(shù)資料
型號: LP55271TLX
廠商: NATIONAL SEMICONDUCTOR CORP
元件分類: 顯示驅(qū)動器
英文描述: Tiny LED Driver for Camera Flash and 4 LEDs with I2C Programmability, Connectivity Test and Audio Synchronization
中文描述: LED DISPLAY DRIVER, PBGA30
封裝: 2.5 X 3 MM, 0.60 MM HEIGHT, BGA-30
文件頁數(shù): 11/21頁
文件大?。?/td> 826K
代理商: LP55271TLX
Flash Driver
LP55271 has an internal constant current driver that is ca-
pable for sinking low (46 mA) and high (370 mA) current
mainly targeted for torch and flash LED in camera phone
applications. 370 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 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.)
Flash driver currents — both torch and flash — are set with
external resistor R
. The flash current is 480/R
amperes
and the torch current is 60/R
amperes. User should not use
lower resistance value than 1200
.
Flash LED Control (X = don’t care)
EN_TORCH bit
0
1
X
EN_FLASH bit
0
0
1
FLASH_SYNC bit or pin
X
X
Change from LOW to HIGH to
engage; from HIGH to LOW to
disengage
SAFETY_TIME bit
X
X
0 for 2.0 seconds;
1 for 1.0 second
Flash LED Action
Off
Torch
Flash
Flash Programming Example
Address
00H
00H
00H
Data
8FH
9FH
FFH
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.
00H
BFH
FLASH DRIVER ELECTRICAL CHARACTERISTICS
Limits in standard typeface are for T
= 25
o
C. Limits in
boldface
type apply over the operating ambient temperature range (-30
o
C
<
T
<
+85
o
C). Unless otherwise noted, specifications apply to the LP55271 Block Diagram with: V
IN
= 3.6V, C
= 10 μF, C
= 10 μF, C
OUT2
= 10 μF, C
VDDIO
= 100 nF, C
VREF
= 100 nF, C
VDDA
= 4.7 μF, C
VDD1
= 100 nF, C
VDD2
= 100 nF, L
1
= 4.7 μH, R
F
= 1300
Symbol
I
FLASH
Parameter
Flash Mode Sink Current
(Note 8)
Torch Mode Sink Current
(Note 8)
Flash Driver Leakage Current
Flash Turn-On Time
(Note 11)
Saturation Voltage
Condition
3.0V
V
IN
5.5V,
V
FLASH
= 1.0V
3.0V
V
IN
5.5V
Min
Typ
370
Max
Units
mA
%
mA
-7.5
+7.5
I
TORCH
46
I
LEAKAGE
t
FLASH
V
FB
= 5.0V
0.1
20
μA
μs
V
SAT
3.0V
V
IN
5.5V,
Current Decreased to 95% of
the Maximum Sink Current
550
mV
t
SAFETY
Safety Time Accuracy
-9
+9
%
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.
L
www.national.com
11
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