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PDF LP3943ISQ Data sheet ( Hoja de datos )
| Número de pieza | LP3943ISQ | |
| Descripción | RGB/White/Blue 16-LED Fun Light Driver | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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November 2003
LP3943
RGB/White/Blue 16-LED Fun Light Driver
General Description
LP3943 is an integrated device capable of independently
driving 16 LEDs. This device also contains an internal pre-
cision oscillator that provides all the necessary timing re-
quired for driving each LED. Two prescaler registers along
with two PWM registers provide a versatile duty cycle con-
trol. The LP3943 contains the ability to dim LEDs in SMBUS/
I2C 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. LP3943 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 Hz–0.625 Hz)
Key Specifications
n 16 LED driver (multiple programmable states — on, off,
input, and dimming at a specified rate)
n 16 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
© 2003 National Semiconductor Corporation DS200796
20079601
www.national.com
1 page  
Electrical Characteristics (Continued)
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, TJ = −40˚C to +125˚C. (Note 5)
Symbol
Parameter
Conditions
Typical
Limit
Min Max
Units
I2C INTERFACE (SCL AND SDA PINS)
tCLK-HP
tSU
CLK High Period
Set-Up Time Repeated
START Condition
(Note 7)
(Note 7)
0.6 µs
0.6 µs
tDATA-HOLD
tDATA-SU
tSU
Data Hold Time
Data Set-Up Time
Set-Up Time for STOP
Condition
(Note 7)
(Note 7)
(Note 7)
300 ns
100 ns
0.6 µs
tTRANS
Maximum Pulse Width of
Spikes that Must Be
(Note 7)
Suppressed by the Input
50 ns
Filter of Both DATA & CLK
Signals
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 part cannot dissipate more than 400mW.
Note 4: The human-body model is 100 pF discharged through 1.5 kΩ. The machine model is 0Ω in series with 100 pF.
Note 5: Limits are guaranteed. All electrical characteristics having room-temperature limits are tested during production with TJ = 25˚C. 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 each octal (LED0–LED7; LED8–LED15) should not exceed 100 mA. The package should not exceed a total
of 200 mA.
Note 7: Guaranteed by design.
Typical Performance Characteristics
Frequency vs. Temp
(TA = −40˚C to +85˚C),
VDD = 2.3V to 3.0V
20079617
5 www.national.com
5 Page 
Application Notes (Continued)
Programming Example:
Dim LEDs 0 to 7 at 1 Hz at 25% duty cycle
Dim LEDs 8 to 12 at 5 Hz at 50% duty cycle
Set LEDs 13, 14 and 15 off
Step 1: Set PSC0 to achieve DIM0 of 1s
Step 2: Set PWM0 duty cycle to 25%
Step 3: Set PSC1 to achieve DIM1 of 0.2s
Step 4: Set PWM1 duty cycle to 50%
Step 5: Set LEDs 13, 14 and 15 off by loading the data into LS3 register
Step 6: Set LEDs 0 to 7 to point to DIM0
Step 7: Set LEDs 8 to 12 to point to DIM1
Step
1
2
3
4
5
6
7
Description
Set DIM0 = 1s
1 = (PSC0 + 1)/160
PSC0 = 159
Set duty cycle to 25%
Duty Cycle = PWM0/256
PWM0 = 64
Set DIM1 = 0.2s
0.2 = (PSC1 + 1)/160
PSC1 = 31
Set duty cycle to 50%
Duty Cycle = PWM1/256
PWM1 = 128
LEDs 13, 14 and 15 off
Output = HIGH
LEDs 0 to 7
Output = DIM0
LEDs 8 to 12
Output = DIM1
Register Name
PSC0
PWM0
PSC1
PWM1
LS3
LS0, LS1
LS2, LS3
Set to (Hex)
0x09F
0x40
0x1F
0x80
0x03
LS0 = 0xAA
LS1 = 0xAA
LS2 = 0xFF
LS3 = 0x03
REDUCING IQ WHEN LEDS ARE OFF
In many applications, the LEDs and the LP3943 share the
same VDD, as shown in Section Typical Application Circuit.
When the LEDs are off, the LED pins are at a lower potential
than VDD, causing extra supply current (∆IQ). To minimize
this current, consider keeping the LED pins at a voltage
equal to or greater than VDD.
FIGURE 9. Methods to Reduce IQ When LEDs Are Off
11
20079614
www.national.com
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet LP3943ISQ.PDF ] | |
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