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PDF LP3936SL Data sheet ( Hoja de datos )
| Número de pieza | LP3936SL | |
| Descripción | Lighting Management System for Six White LEDs and One RGB or FLASH LED | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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June 2004
LP3936
Lighting Management System for Six White LEDs and
One RGB or FLASH LED
General Description
LP3936 is a complete lighting management system de-
signed for portable wireless applications. It contains a boost
DC/DC converter, 4 white LED drivers to drive the main LCD
panel backlight, 2 white LED drivers for sub-LCD panel and
1 set of RGB LED drivers.
Both WLED groups have 8-bit programmable constant cur-
rent drivers that are separately adjustable and matched to
1% (typ.). For efficient backlighting the backlight intensity
can be adjusted using the 8-bit ADC with ambient light
detection circuit.
The RGB LED drivers are PWM-driven with programmable
color, intensity and blinking patterns. In addition, they feature
a FLASH function to support picture taking with camera-
enabled cellular phones.
An efficient magnetic boost converter provides the required
bias operating from a single Li-Ion battery. The DC/DC con-
verter output voltage is user programmable for adapting to
different LED types and for efficiency optimization. All func-
tions are software controllable through an I2C and
MicroWire/SPI compatible interface and 16 internal regis-
ters.
Features
n High Efficiency 250 mA Magnetic Boost DC-DC
Converter with Programmable Output Voltage
n PWM controlled RGB LED drivers with programmable
color, brightness, turn on/off slopes and blinking
n FLASH function with 3 drivers, each up to 120 mA
current
n 4 constant current White LED drivers with
programmable 8-bit adjustment (0 … 25 mA/LED)
n 2 constant current White LED drivers with
programmable 8-bit adjustment (0 … 25 mA/LED)
n 8-bit ADC for ambient light sensor with averaging
n Combined MicroWire/SPI and I2C compatible serial
interface
n Low current Standby mode (software controlled)
n Low voltage digital interface down to 1.8V
n Space efficient 32-pin thin CSP laminate package
Applications
n Cellular Phones
n PDAs
Typical Application
© 2004 National Semiconductor Corporation DS200814
20081401
www.national.com
1 page  
Electrical Characteristics (Notes 2, 8) (Continued)
Note 6: In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may have to be
derated. Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction temperature (TJ-MAX-OP = 125˚C), the maximum power
dissipation of the device in the application (PD-MAX), and the junction-to ambient thermal resistance of the part/package in the application (θJA), as given by the
following equation: TA-MAX = TJ-MAX-OP − (θJA x PD-MAX).
Note 7: Junction-to-ambient thermal resistance is highly application and board-layout dependent. In applications where high maximum power dissipation exists,
special care must be paid to thermal dissipation issues in board design.
Note 8: Min and Max limits are guaranteed by design, test, or statistical analysis. Typical numbers are not guaranteed, but do represent the most likely norm.
Note 9: Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) are used in setting electrical characteristics.
Note 10: VREF pin (Bandgap reference output) is for internal use only. A capacitor should always be placed between VREF and GND1.
Block Diagram
20081405
5 www.national.com
5 Page 
I2C Compatible Interface (Continued)
I2C Timing Parameters
VDD1, 2 = 3.0V to 4.5V, VDD_IO = 1.8V to VDD1, 2
Symbol
Parameter
1 Hold Time (repeated) START Condition
2 Clock Low Time
3 Clock High Time
4 Setup Time for a Repeated START Condition
5 Data Hold Time
6 Data Setup Time
7 Rise Time of SDA and SCL
8 Fall Time of SDA and SCL
9 Set-Up Time for STOP Condition
10 Bus Free Time between a STOP and a START Condition
Cb Capacitive Load for Each Bus Line
Note: Data guaranteed by design.
Limits
Min Max
0.6
1.3
600
600
300 900
100
20 + 0.1Cb
15 + 0.1Cb
600
300
300
1.3
10 200
Units
µs
µs
ns
ns
ns
ns
ns
ns
ns
µs
pF
A/D Converter for Ambient Light Measurement
Electrical Characteristics
Symbol
VIN RANGE
Parameter
Input Voltage
DNL
GE
PSS
f(conv)
Differential Non-Linearity
Gain Error
Power Supply Sensitivity
Conversion Rate
tSTARTUP
IAIN
IAREF
RAREF
Startup Time
Input Current
Maximum Output Current
AREF Output Resistance
Conditions
AD Output: 00h
AD Output: FFh
3.1V ≤ VDD ≤ 4.2V
Without Averaging
With Averaging
(64 samples)
1.23 < AIN < 2.6V
AREF Output Current Sink
Min Typ Max Units
1.23
V
2.46
V
–1.5
±1
+1.5
LSB
−5 +5 LSB
±1/2
LSB
217 Hz
3.4 Hz
100
±0.1
200
110
ms
µA
µA
Ω
ADC output AIN[7:0] can be read from address 0CH after startup time. Overflow bit can be read from bit D7 in address 0BH. The
overflow bit indicates that input voltage exceeds the input voltage range of the ADC. The ADC output value in this case is FFH.
When averaging is on, the overflow is high, if any of the 64 conversion results in the averaging period overflows. Thus the
averaged result may be considerably below maximum and the overflow can still be high, if the input signal is noisy.
Examples for optical sensor are photodiode SHF2400 and phototransistor SFH3410 from Osram or BSC 3216 G1 optical sensor
from TDK.
ADC can be used for temperature measurement with a thermistor. It enables temperature compensated LED driving.
If ADC is not used, it should be disabled by writing en_ambadc bit low. AIN and AREF pins can be left unconnected
11 www.national.com
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| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LP3936SL.PDF ] | |
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