TPS72118DBVT-TI - TEXAS INSTRUMENTS

LP3944

LP3944 RGB/White/Blue 8-LED Fun Light Driver

Literature Number: SNVS264

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

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

nInternal power-on reset

nActive low reset

nInternal precision oscillator

nVariable dim rates (from 6.25 ms to 1.6s;

160 Hz–0.625 Hz)

Key Specifications

n8 LED driver (multiple programmable states — on, off,

input, and dimming at a specified rate)

n8 Open drain outputs capable of driving up to 25 mA per

LED

Applications

nCustomized flashing LED lights for cellular phones

nPortable Applications

nDigital Cameras

nIndicator Lamps

nGeneral purpose I/O expander

nToys

Typical Application Circuit

20085301

November 2003

LP3944 RGB/White/Blue 8-LED Fun Light Driver

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

C Interface

20 SDA Serial Data Line for I

C Interface

21 V

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

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Architectural Block Diagram

20085303

For Explanation of LP3944 Operation, Please Refer to “Theory of Operation” in Application Notes.

LP3944

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Absolute Maximum Ratings (Notes 2,

If Military/Aerospace specified devices are required,

please contact the National Semiconductor Sales Office/

Distributors for availability and specifications.

−0.5V to 6V

A0, A1, A2, SCL, SDA, RST

(Collectively called digital pins)

Voltage on LED pins V

−0.5V to 6V

Junction Temperature 150˚C

Storage Temperature −65˚C to 150˚C

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)

2.3V to 5.5V

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

Electrical Characteristics

Unless otherwise noted, V

= 5.5V. Typical values and limits appearing in normal type apply for T

= 25˚C. Limits appearing

in boldface type apply over the entire junction temperature range for operation, T

= −40˚C to +125˚C. (Note 5)

Symbol Parameter Conditions Typical Limit Units

Min Max

POWER SUPPLY

Supply Voltage 5 2.3 5.5 V

Supply Current No Load 350 550 µA

Standby 2.0 5

∆I

Additional Standby Current V

= 5.5V, every LED pin

at 4.3V 2mA

POR

Power-On Reset Voltage 1.8 1.96 V

Reset Pulse Width 10 ns

LED

LOW Level Input Voltage −0.5 0.8 V

HIGH Level Input Voltage 2.0 5.5 V

Low Level Output Current

(Note 6)

= 0.4V, V

= 2.3V 9

= 0.4V, V

= 3.0V 12

= 0.4V, V

= 5.0V 15

= 0.7V, V

= 2.3V 15

= 0.7V, V

= 3.0V 20

= 0.7V, V

= 5.0V 25

LEAK

Input Leakage Current V

= 3.6, V

=0VorV

−1 1 µA

I/O

Input/Output Capacitance (Note 7) 2.6 5pF

ALL DIGITAL PINS (EXCEPT SCL AND SDA PINS)

LOW Level Input Voltage −0.5 0.8 V

HIGH Level Input Voltage 2.0 5.5 V

LEAK

Input Leakage Current −1 1 µA

Input Capacitance V

= 0V (Note 7) 2.3 5pF

C INTERFACE (SCL AND SDA PINS)

LOW Level Input Voltage -0.5 0.3V

HIGH Level Input Voltage 0.7V

5.5 V

LOW Level Output Voltage 0 0.2V

LOW Level Output Current V

= 0.4V 6.5 3mA

CLK

Clock Frequency (Note 7) 400 kHz

HOLD

Hold Time Repeated START

Condition

(Note 7) 0.6 µs

LP3944

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Electrical Characteristics (Continued)

Unless otherwise noted, V

= 5.5V. Typical values and limits appearing in normal type apply for T

= 25˚C. Limits appearing

in boldface type apply over the entire junction temperature range for operation, T

= −40˚C to +125˚C. (Note 5)

Symbol Parameter Conditions Typical Limit Units

Min Max

C INTERFACE (SCL AND SDA PINS)

CLK-LP

CLK Low Period (Note 7) 1.3 µs

CLK-HP

CLK High Period (Note 7) 0.6 µs

Set-Up Time Repeated

START Condition

(Note 7) 0.6 µs

DATA-HOLD

Data Hold Time (Note 7) 300 ns

DATA-SU

Data Set-Up Time (Note 7) 100 ns

Set-Up Time for STOP

Condition

(Note 7) 0.6 µs

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)/θJA, (1)

where TJis the junction temperature, TAis the ambient temperature, and θJA is the junction-to-ambient thermal resistance. The 1.76W rating appearing under

Absolute Maximum Ratings results from substituting the Absolute Maximum junction temperature, 150˚C, for TJ, 85˚C for TA, and 37˚C/W for θJA. More power can

be dissipated safely at ambient temperature below 85˚C. Less power can be dissipated safely at ambient temperatures above 85˚C. The Absolute Maximum power

dissipation can be increased by 27 mW for each degree below 85˚C, and it must be de-rated by 27 mW for each degree above 85˚C. For Operating Ratings

maximum power dissipation, TJ= 125˚C and TA= 85˚C

Note 4: The human-body model is 100 pF discharged through 1.5 kΩ. The machine model is 0Ωin series with 220 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 the package should not exceed a total of 200 mA.

Note 7: Guaranteed by design.

Typical Performance Characteristics

Frequency vs. Temp

= −40˚C to +85˚C),

= 2.3V to 3.0V

20085317

LP3944

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Application Notes

THEORY OF OPERATION

The LP3944 takes incoming data and feed them into several

registers that control the frequency and the duty cycle of the

LEDs. Two prescaler registers and two PWM registers pro-

vide two individual rates to dim or blink the LEDs (for more

information on these registers, refer to Table 1. LP3944

microprocessor can program each LED to be in one of four

states — on, off, DIM0 rate or DIM1 rate. One read-only

registers provide status on all 8 LEDs. The LP3944 can be

used to drive RGB LEDs and/or single-color LEDs to create

a colorful, entertaining, and informative setting. This is par-

ticularly suitable for accessory functions in cellular phones

and toys. Any LED pins not used to drive LED can be used

for General Purpose Parallel Input/Output (GPIO) expan-

sion.

The LP3944 is equipped with Power-On Reset that holds the

chip in a reset state until V

reaches V

POR

during power up.

Once V

POR

is achieved, the LP3944 comes out of reset and

initializes itself to the default state.

To bring the LP3944 into reset, hold the RST pin LOW for a

period of TW. This will put the chip to its default state. The

LP3944 can only be programmed after RST signal is HIGH

again.

C DATA VALIDITY

The data on SDA line must be stable during the HIGH period

of the clock signal (SCL). In other words, state of the data

line can only be changed when CLK is LOW.

C START AND STOP CONDITIONS

START and STOP bits classify the beginning and the end of

the I

C session. START condition is defined as SDA signal

transitioning from HIGH to LOW while SCL line is HIGH.

STOP condition is defined as the SDA transitioning from

LOW to HIGH while SCL is HIGH. The I

C master always

generates START and STOP bits. The I

C bus is considered

to be busy after START condition and free after STOP con-

dition. During data transmission, I

C master can generate

repeated START conditions. First START and repeated

START conditions are equivalent, function-wise.

TRANSFERRING DATA

Every byte put on the SDA line must be eight bits long with

the most significant bit (MSB) being transferred first. The

number of bytes that can be transmitted per transfer is

unrestricted. Each byte of data has to be followed by an

acknowledge bit. The acknowledge related clock pulse is

generated by the master. The transmitter releases the SDA

line (HIGH) during the acknowledge clock pulse. The re-

ceiver must pull down the SDA line during the 9th clock

pulse, signifying an acknowledge. A receiver which has been

addressed must generate an acknowledge after each byte

has been received.

After the START condition, a chip address is sent by the I

master. This address is seven bits long followed by an eighth

bit which is a data direction bit (R/W). The LP3944 hardwires

bits 7 to 4 and leaves bits 3 to 1 selectable, as shown in

Figure 3. For the eighth bit, a “0” indicates a WRITE and a

“1” indicates a READ. The LP3944 supports only a WRITE

during chip addressing. The second byte selects the register

to which the data will be written. The third byte contains data

to write to the selected register.

20085306

FIGURE 1. I

C Data Validity

20085307

FIGURE 2. I

C START and STOP Conditions

LP3944

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Application Notes (Continued)

However, if a READ function is to be accomplished, a

WRITE function must precede the READ function, as shown

in Figure 5.

20085308

FIGURE 3. Chip Address Byte

20085309

w = write (SDA = “0”)

r = read (SDA = “1”)

ack = acknowledge (SDA pulled down by either master or slave)

rs = repeated start

xx=60to67

FIGURE 4. LP3944 Register Write

20085310

w = write (SDA = “0”)

r = read (SDA = “1”)

ack = acknowledge (SDA pulled down by either master or slave)

rs = repeated start

xx=60to67

FIGURE 5. LP3944 Register Read

LP3944

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Application Notes (Continued)

AUTO INCREMENT

Auto increment is a special feature supported by the LP3944

to eliminate repeated chip and register addressing when

data are to be written to or read from registers in sequential

order. The auto increment bit is inside the register address

byte, as shown in Figure 6. Auto increment is enabled when

this bit is programmed to “1” and disabled when it is pro-

grammed to “0”.

In the READ mode, when auto increment is enabled, I

master could receive any number of bytes from LP3944

without selecting chip address and register address again.

Every time the I

C master reads a register, the LP3944 will

increment the register address and the next data register will

be read. When I

C master reaches the last register (09H

In the WRITE mode, when auto increment is enabled, the

LP3944 will increment the register address every time I

master writes to register. When the last register (09H regis-

ter) is reached, the register address will roll over to 02H,

because the first two registers in LP3944 are read-only

registers. It is possible to write to these two registers, and the

LP3944 will acknowledge, but the data will be ignored.

In the LP3944, registers 0x01, 0x08 and 0x09 are not func-

tional. However, it is still necessary to read from 0x01 and to

write to 0x08 and 0x09 in Auto Increment mode. They cannot

be skipped.

If auto increment is disabled, and the I

C master does not

change register address, it will continue to write data into the

same register.

20085311

FIGURE 6. Register Address Byte

20085312

FIGURE 7. Programming with Auto Increment Disabled (in WRITE Mode)

20085313

FIGURE 8. Programming with Auto Increment Enabled (in WRITE Mode)

LP3944

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Application Notes (Continued)

TABLE 1. LP3944 REGISTER TABLE

Address (Hex) Register Name Read/Write Register Function

0x00 Input 1 Read Only LED0–7 Input Register

0x01 Register 1 Read Only None

0x02 PSC0 R/W Frequency Prescaler 0

0x03 PWM0 R/W PWM Register 0

0x04 PSC1 R/W Frequency Prescaler 1

0x05 PWM1 R/W PWM Register 1

0x06 LS0 R/W LED0–3 Selector

0x07 LS1 R/W LED4–7 Selector

0x08 Register 8 R/W None

0x09 Register 9 R/W None

Note: Registers 1, 8 and 9 are empty and non-functional registers. Register 1 is read-only, with all bits hard-wired to zero. Registers 8 and 9 can be written and read,

but the content does ot have any effect on the operation of the LP3944.

BINARY FOMAT FOR INPUT REGISTERS (READ ONLY) — ADDRESS 0x00 and 0x01

Address 0x00

Bit# 76543210

Default value XXXXXXXX

LED7 LED6 LED5 LED4 LED3 LED2 LED1 LED0

X = don’t care

BINARY FORMAT FOR FREQUENCY PRESCALER AND PWM REGISTERS — ADDRESS 0x02 to 0x05

Address 0x02 (PSC0)

Bit# 76543210

Default value 00000000

PSC0 register is used to program the period of DIM0.

DIM0 = (PSC0+1)/160

The maximum period is 1.6s when PSC0 = 255.

Address 0x03 (PWM0)

Bit# 76543210

Default value 10000000

PWM0 register determines the duty cycle of DIM0. The LED outputs are LOW (LED on) when the count is less than the value in PWM0 and HIGH (LED off) when

it is greater. If PWM0 is programmed with 0x00, LED output is always HIGH (LED off).

The duty cycle of DIM0 is: PWM0/256

Default value is 50% duty cycle.

Address 0x04 (PSC1)

Bit# 76543210

Default value 00000000

PSC1 register is used to program the period of DIM1.

DIM1 = (PSC1 + 1)/160

The maximum period is 1.6s when PSC1 = 255.

LP3944

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Application Notes (Continued)

Address 0x05 (PWM1)

Bit# 76543210

Default value 10000000

PWM1 register determines the duty cycle of DIM1. The LED outputs are LOW (LED on) when the count is less than the value in PWM1 and HIGH (LED off) when

it is greater. If PWM1 is programmed with 0x00, LED output is always HIGH (LED off).

The duty cycle of DIM1 is: PWM1/256

Default value is 50% duty cycle.

BINARY FORMAT FOR SELECTOR REGISTERS — ADDRESS 0x06 to 0x07

Address 0x06 (LS0)

Bit# 76543210

Default value 00000000

B1 B0 B1 B0 B1 B0 B1 B0

LED3 LED2 LED1 LED0

Address 0x07 (LS1)

Bit# 76543210

Default value 00000000

B1 B0 B1 B0 B1 B0 B1 B0

LED7 LED6 LED5 LED4

LED States With Respect To Values in "B1" and "B0"

B1 B0 Function

0 0 Output Hi-Z

(LED off)

0 1 Output LOW

(LED on)

1 0 Output dims

(DIM0 rate)

1 1 Output dims

(DIM1 rate)

Programming Example:

Dim LEDs 0 to 7 at 1 Hz at 25% duty cycle

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 LEDs 0 to 7 to point to DIM0

Step Description Register Name Set to (Hex)

1 Set DIM0 = 1s

1 = (PSC0 + 1)/160

PSC0 = 159

PSC0 0x09F

2 Set duty cycle to 25%

Duty Cycle = PWM0/256

PWM0 = 64

PWM0 0x40

3 Set DIM1 = 0.2s

0.2 = (PSC1 + 1)/160

PSC1 = 31

PSC1 0x1F

4 LEDs0to7

Output = DIM0

LS0, LS1 LS0 = 0xAA

LS1 = 0xAA

LP3944

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Application Notes (Continued)

REDUCING I

WHEN LEDS ARE OFF

In many applications, the LEDs and the LP3944 share the

same V

, as shown in Section Typical Application Circuit.

When the LEDs are off, the LED pins are at a lower potential

than V

, causing extra supply current (∆I

). To minimize

this current, consider keeping the LED pins at a voltage

equal to or greater than V

Application Circuit

20085315

20085314

FIGURE 9. Methods to Reduce I

When LEDs Are Off

LP3944

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Physical Dimensions inches (millimeters) unless otherwise noted

NOTES: UNLESS OTHERWISE SPECIFIED

1. FOR LEAD FINISH THICKNESS AND COMPOSITION. SEE “SOLDER INFORMATION” IN THE PACKAGING SECTION

OF THE NATIONAL SEMICONDUCTOR WEB PAGE (www. national.com).

2. NO JEDEC REGISTRATION AS OF MARCH 2003.

Order Number LP3944ISQ or LP3944ISQX

NS Package Number SQA24C

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2. A critical component is any component of a life

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LP3944 RGB/White/Blue 8-LED Fun Light Driver

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