National Semiconductor LP3944 Technical data
LP3944
RGB/White/Blue 8-LED Fun Light Driver
LP3944 RGB/White/Blue 8-LED Fun Light Driver
November 2003
General Description
LP3944 is an integrated device capable of independently
driving 8 LEDs. This device also contains an internal precision oscillator that provides all the necessary timing required
for driving each LED. Two prescaler registers along with two
PWM registers provide a versatile duty cycle control. The
LP3944 contains the ability to dim LEDs in SMBUS/I
applications where it is required to cut down on bus traffic.
Traditionally, to dim LEDs using a serial shift register such as
74LS594/5 would require a large amount of traffic to be on
the serial bus. LP3944 instead requires only the setup of the
frequency and duty cycle for each output pin. From then on,
only a single command from the host is required to turn each
individual open drain output ON, OFF, or to cycle a programmed frequency and duty cycle. Maximum output sink
current is 25 mA per pin and 200 mA per package. Any ports
not used for controlling the LEDs can be used for general
purpose input/output expansion.
2
Typical Application Circuit
Features
n Internal power-on reset
n Active low reset
n Internal precision oscillator
n Variable dim rates (from 6.25 ms to 1.6s;
160 Hz– 0.625 Hz)
C
Key Specifications
n 8 LED driver (multiple programmable states — on, off,
input, and dimming at a specified rate)
n 8 Open drain outputs capable of driving up to 25 mA per
LED
Applications
n Customized flashing LED lights for cellular phones
n Portable Applications
n Digital Cameras
n Indicator Lamps
n General purpose I/O expander
n Toys
20085301
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LP3944 Pin Out
LP3944
(Top View)
See NS Package Number SQA24A
LP3944 Pin Description
Pin # Name Description
1 LED0 Output of LED0 Driver
2 LED1 Output of LED1 Driver
3 LED2 Output of LED2 Driver
4 LED3 Output of LED3 Driver
5 LED4 Output of LED4 Driver
6 LED5 Output of LED5 Driver
7 LED6 Output of LED6 Driver
8 LED7 Output of LED7 Driver
9 GND Ground
10 NC No Connect
11 NC No Connect
12 NC No Connect
13 NC No Connect
14 NC No Connect
15 NC No Connect
16 NC No Connect
17 NC No Connect
18 RST
19 SCL Clock Line for I
20 SDA Serial Data Line for I
21 V
22 A0 Address Input 0
23 A1 Address Input 1
24 A2 Address Input 2
DD
Active Low Reset Input
Power Supply
2
C Interface
2
C Interface
20085302
Ordering Information
LP3944, Supplied as 1000 Units, Tape and
Reel
LP3944ISQ LP3944ISQX
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LP3944, Supplied as 4500 Units, Tape
and Reel
Package Marking
Architectural Block Diagram
LP3944
For Explanation of LP3944 Operation, Please Refer to “Theory of Operation” in Application Notes.
20085303
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Absolute Maximum Ratings (Notes 2,
1)
LP3944
If Military/Aerospace specified devices are required,
Human Body Model 2 kV
Machine Model 150V
Charge Device Model 1 kV
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
V
DD
−0.5V to 6V
A0, A1, A2, SCL, SDA, RST
(Collectively called digital pins)
Voltage on LED pins V
−0.5V to 6V
SS
Junction Temperature 150˚C
Storage Temperature −65˚C to 150˚C
Power Dissipation (Note 3) 1.76W
6V
Operating Ratings (Notes 1, 2)
V
DD
Junction Temperature −40˚C to +125˚C
Operating Ambient Temperature −40˚C to +85˚C
Thermal Resistance (θ
LLP24 (Note 3) 37˚C/W
Power Dissipation 1.08W
)
JA
ESD (Note 4)
Electrical Characteristics
Unless otherwise noted, VDD= 5.5V. Typical values and limits appearing in normal type apply for TJ= 25˚C. Limits appearing
in boldface type apply over the entire junction temperature range for operation, T
Symbol Parameter Conditions Typical
POWER SUPPLY
V
DD
I
Q
Supply Voltage 5 2.3 5.5 V
Supply Current No Load 350 550
Standby 2.0 5
∆I
Q
Additional Standby Current VDD= 5.5V, every LED pin
at 4.3V
V
POR
t
w
Power-On Reset Voltage 1.8 1.96 V
Reset Pulse Width 10 ns
LED
V
IL
V
IH
I
OL
LOW Level Input Voltage −0.5 0.8 V
HIGH Level Input Voltage 2.0 5.5 V
Low Level Output Current
VOL= 0.4V, VDD= 2.3V
(Note 6)
VOL= 0.4V, VDD= 3.0V 12
V
= 0.4V, VDD= 5.0V 15
OL
V
= 0.7V, VDD= 2.3V 15
OL
V
= 0.7V, VDD= 3.0V 20
OL
V
= 0.7V, VDD= 5.0V 25
OL
I
LEAK
C
I/O
Input Leakage Current VDD= 3.6, VIN=0VorV
DD
Input/Output Capacitance (Note 7) 2.6 5 pF
ALL DIGITAL PINS (EXCEPT SCL AND SDA PINS)
V
IL
V
IH
I
LEAK
C
IN
2
I
C INTERFACE (SCL AND SDA PINS)
V
IL
V
IH
V
OL
I
OL
F
CLK
t
HOLD
LOW Level Input Voltage −0.5 0.8 V
HIGH Level Input Voltage 2.0 5.5 V
Input Leakage Current −1 1 µA
Input Capacitance VIN= 0V (Note 7) 2.3 5 pF
LOW Level Input Voltage -0.5 0.3V
HIGH Level Input Voltage 0.7V
LOW Level Output Voltage 0 0.2V
LOW Level Output Current VOL= 0.4V 6.5 3 mA
Clock Frequency (Note 7) 400 kHz
Hold Time Repeated START
(Note 7)
Condition
= −40˚C to +125˚C. (Note 5)
J
Limit
Min Max
9
−1 1 µA
DD
0.6 µs
2 mA
DD
5.5 V
DD
2.3V to 5.5V
Units
µA
mA
V
V
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