LP3944
RGB/White/Blue 8-LED Fun Light Driver
General Description
LP3944 is an integrated device capable of independently
driving 8 LEDs. This device also contains an internal preci-
sion 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
2
C
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 pro-
grammed 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.
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 Hz0.625 Hz)
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
Typical Application Circuit
20085301
November 2003
LP3944
RGB/White/Blue
8-LED
Fun
Light
Driver
2003 National Semiconductor Corporation
DS200853
www.national.com
LP3944 Pin Out
20085302
(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
Active Low Reset Input
19
SCL
Clock Line for I
2
C Interface
20
SDA
Serial Data Line for I
2
C Interface
21
V
DD
Power Supply
22
A0
Address Input 0
23
A1
Address Input 1
24
A2
Address Input 2
Ordering Information
LP3944, Supplied as 1000 Units, Tape and
Reel
LP3944, Supplied as 4500 Units, Tape
and Reel
Package Marking
LP3944ISQ
LP3944ISQX
LP3944
www.national.com
2
Absolute Maximum Ratings
(Notes 2,
1)
If Military/Aerospace specified devices are required,
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)
6V
Voltage on LED pins
V
SS
-0.5V to 6V
Junction Temperature
150C
Storage Temperature
-65C to 150C
Power Dissipation (Note 3)
1.76W
ESD (Note 4)
Human Body Model
2 kV
Machine Model
150V
Charge Device Model
1 kV
Operating Ratings
(Notes 1, 2)
V
DD
2.3V to 5.5V
Junction Temperature
-40C to +125C
Operating Ambient Temperature
-40C to +85C
Thermal Resistance (
JA
)
LLP24 (Note 3)
37C/W
Power Dissipation
1.08W
Electrical Characteristics
Unless otherwise noted, V
DD
= 5.5V. Typical values and limits appearing in normal type apply for T
J
= 25C. Limits appearing
in boldface type apply over the entire junction temperature range for operation, T
J
= -40C to +125C. (Note 5)
Symbol
Parameter
Conditions
Typical
Limit
Units
Min
Max
POWER SUPPLY
V
DD
Supply Voltage
5
2.3
5.5
V
I
Q
Supply Current
No Load
350
550
A
Standby
2.0
5
I
Q
Additional Standby Current
V
DD
= 5.5V, every LED pin
at 4.3V
2
mA
V
POR
Power-On Reset Voltage
1.8
1.96
V
t
w
Reset Pulse Width
10
ns
LED
V
IL
LOW Level Input Voltage
-0.5
0.8
V
V
IH
HIGH Level Input Voltage
2.0
5.5
V
I
OL
Low Level Output Current
(Note 6)
V
OL
= 0.4V, V
DD
= 2.3V
9
mA
V
OL
= 0.4V, V
DD
= 3.0V
12
V
OL
= 0.4V, V
DD
= 5.0V
15
V
OL
= 0.7V, V
DD
= 2.3V
15
V
OL
= 0.7V, V
DD
= 3.0V
20
V
OL
= 0.7V, V
DD
= 5.0V
25
I
LEAK
Input Leakage Current
V
DD
= 3.6, V
IN
= 0V or V
DD
-1
1
A
C
I/O
Input/Output Capacitance
(Note 7)
2.6
5
pF
ALL DIGITAL PINS (EXCEPT SCL AND SDA PINS)
V
IL
LOW Level Input Voltage
-0.5
0.8
V
V
IH
HIGH Level Input Voltage
2.0
5.5
V
I
LEAK
Input Leakage Current
-1
1
A
C
IN
Input Capacitance
V
IN
= 0V (Note 7)
2.3
5
pF
I
2
C INTERFACE (SCL AND SDA PINS)
V
IL
LOW Level Input Voltage
-0.5
0.3V
DD
V
V
IH
HIGH Level Input Voltage
0.7V
DD
5.5
V
V
OL
LOW Level Output Voltage
0
0.2V
DD
V
I
OL
LOW Level Output Current
V
OL
= 0.4V
6.5
3
mA
F
CLK
Clock Frequency
(Note 7)
400
kHz
t
HOLD
Hold Time Repeated START
Condition
(Note 7)
0.6
s
LP3944
www.national.com
4
Electrical Characteristics
(Continued)
Unless otherwise noted, V
DD
= 5.5V. Typical values and limits appearing in normal type apply for T
J
= 25C. Limits appearing
in boldface type apply over the entire junction temperature range for operation, T
J
= -40C to +125C. (Note 5)
Symbol
Parameter
Conditions
Typical
Limit
Units
Min
Max
I
2
C INTERFACE (SCL AND SDA PINS)
t
CLK-LP
CLK Low Period
(Note 7)
1.3
s
t
CLK-HP
CLK High Period
(Note 7)
0.6
s
t
SU
Set-Up Time Repeated
START Condition
(Note 7)
0.6
s
t
DATA-HOLD
Data Hold Time
(Note 7)
300
ns
t
DATA-SU
Data Set-Up Time
(Note 7)
100
ns
t
SU
Set-Up Time for STOP
Condition
(Note 7)
0.6
s
t
TRANS
Maximum Pulse Width of
Spikes that Must Be
Suppressed by the Input
Filter of Both DATA & CLK
Signals
(Note 7)
50
ns
Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of the device
is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the Electrical
Characteristics tables.
Note 2: All voltages are with respect to the potential at the GND pin.
Note 3: The Absolute Maximum power dissipation depends on the ambient temperature and can be calculated using the formula
P = (T
J
-- T
A
)/
JA
,
(1)
where T
J
is the junction temperature, T
A
is the ambient temperature, and
JA
is the junction-to-ambient thermal resistance. The 1.76W rating appearing under
Absolute Maximum Ratings results from substituting the Absolute Maximum junction temperature, 150C, for T
J
, 85C for T
A
, and 37C/W for
JA
. More power can
be dissipated safely at ambient temperature below 85C. Less power can be dissipated safely at ambient temperatures above 85C. The Absolute Maximum power
dissipation can be increased by 27 mW for each degree below 85C, and it must be de-rated by 27 mW for each degree above 85C. For Operating Ratings
maximum power dissipation, T
J
= 125C and T
A
= 85C
Note 4: The human-body model is 100 pF discharged through 1.5 k
. The machine model is 0 in series with 220 pF.
Note 5: Limits are guaranteed. All electrical characteristics having room-temperature limits are tested during production with T
J
= 25C. All hot and cold limits are
guaranteed by correlating the electrical characteristics to process and temperature variations and applying statistical process control.
Note 6: Each LED pin should not exceed 25 mA and the package should not exceed a total of 200 mA.
Note 7: Guaranteed by design.
Typical Performance Characteristics
Frequency vs. Temp
(T
A
= -40C to +85C),
V
DD
= 2.3V to 3.0V
20085317
LP3944
www.national.com
5
PDF 
ZIP