Functional description

LP3944 is an integrated device that can internal power and reset 8 LEDs. This device is also

Low -reset with a low -reset contains an internal precision oscillator, which provides an internal precision oscillator driver each variable tone (from 6.25 ms to 1.6s; 160 LED. Two pre -scorers. The register and two PWM Hertz registers provide a universal duty cycle control. 0.625 Hz) LP3944 has a function SMBUS/I2C application that has the darker LED, and applications that need to reduce bus traffic.

Traditional honeycomb custom flash LED lights, use 74LS594/5 serial displacement register calls to darke the LED, need a large number of portable applications on the serial bus. Change to LP3944

Digital camera only needs to set frequency and duty cycle of each output pin cycle. From then on, just send a

indicator light command from the host to turn on each indicator

General I/O extensor single road leakage output, off, or cycle A #8226; Toys programming frequency and duty occupation ratio. The maximum output leakage current is 25 mAh per pin and 200 mAh key specifications per pin. Any port that is not used to control LEDs can be used for universal input/output

8 LED drives (multiple programmable extensions. Status, customs, input, and darkening specified rates)

Eight leakage outputs can drive up to up to each LED 25 mAh

(1) The absolute maximum rated value refers to the limit value of the device. Rate -running value refers to ensuring the operation of the device. Running rated values u200bu200bdo not mean guarantee performance restrictions. Ensure performance restrictions and related test conditions, see electrical characteristics tables.

(2) All voltages are relative to GND.

(3) If you need special equipment for military/aerospace, please contact Texas Instruments to understand availability and specifications.

(4) Absolutely maximum power consumption depends on the environmental temperature. You can use formula calculations u003d (TJ-TA)/θJa, where TJ is the knot temperature, TA is the ambient temperature, θja is the resistance of the environmental heat. Essence The 1.76W rated value that appears under the maximum rated value is the result temperature replaced by absolute maximum knot replacement. TJ is 150 ° C, TA is 85 ° C, and θja is 37 ° C/W. When the ambient temperature is lower than 85 ° C, it can safely dissipate more power. At the ambient temperature higher than 85 ° C, it can safely consume less power. It can increase the absolute maximum power consumption of 27 MW per degree per degree, and the rated work of 27 MW must be reduced when it is higher than 85 degrees Celsius.The maximum power consumption, TJ u003d 125 ° C and TA u003d 85 ° C

(5) The human model is 100 PF, discharge through 1.5 k The machine model is 0 and 220 PF.

(1) Absolute maximum rated value refers to the limit value that may be damaged by the device. Rate -running value refers to ensuring the operation of the device. Running rated values u200bu200bdo not mean guarantee performance restrictions. Ensure performance restrictions and related test conditions, see electrical characteristics tables.

(2) All voltages are relative to GND.

(3) Absolutely maximum power consumption depends on the environmental temperature. You can use formula calculations u003d (TJ-TA)/θJa, where TJ is the knot temperature, TA is the ambient temperature, θja is the resistance of the environmental heat. Essence The 1.76W rated value that appears under the maximum rated value is the result temperature replaced by absolute maximum knot replacement. TJ is 150 ° C, TA is 85 ° C, and θja is 37 ° C/W. When the ambient temperature is lower than 85 ° C, it can safely dissipate more power. At the ambient temperature higher than 85 ° C, it can safely consume less power. It can increase the absolute maximum power consumption of 27 MW per degree per degree. When it is higher than 85 degrees Celsius, the maximum power consumption of the rated power of 27 MW must be reduced. TJ u003d 125 ° C and TA u003d 85 ° C

[ 123] Electrical features

Unless otherwise explained, VDD u003d 5.5V. The typical values u200bu200band limits in normal types are suitable for TJ u003d 25 ° C. The limits of black bodies are suitable for the entire temperature range, TJ u003d 40 ° C to+125 ° C. (1)

(1) The limit is guaranteed. All electrical properties with room temperature restrictions are tested during the production process of TJ u003d 25 ° C By the combination of electrical characteristics and process and temperature changes and apply statistical methods to ensure the cold limit process control.

(2) Each LED pin must not exceed 25 mAh, and the total encapsulation current must not exceed 200 mAh.

(3) Design Guarantee

Operation Theory

LP3944 receives the input data and enter them in several registers. Essence Two pre -scoring registers and two PWM registers provide two separate rates to darkerate or flash LED (more information about these registers, see Table 1). The baseband controller/microprocessor can be one of the four states: ON, OFF, DIM0 Rate or DIM1 Rate. A reader only provides all 8 LEDs. LP3944 can be used to drive RGB LED and/or monochrome LED, creating color, entertainment and informatious environment. This is especially suitable for mobile phones and toys. Any LED pins that are not used to drive LEDs can be used for parallel input/output (GPIO) expansion. The LP3944 is equipped with power -on resetting function, so that the chip is in a reset state until VDD reaches VPOR power generation. Once VPOR is implemented, LP3944 will exit and reset and initialize itself into the default state. To restore the LP3944, keep the first pins at a low time for a period of time. This will make the chip in the default state. LP3944 can only be programmed at high levels at the RST signal again.

I2C data validity

The data on the SDA line must be stable in the clock signal (SCL). In other words, the status data cable can only be changed when CLK is low.

I2C start and stop condition

Starting and stopping bit of the start and end of the I2C session. The start -up condition is defined as the SDASCL line high -time signal from high to low. The stop condition is defined as a transition from low to high when SDASCL is high. The I2C host always generates a startup bit and stop bit. I2C bus is considered busy after starting, and it is idle after stopping. During the data period, the I2C host can generate repeated startup conditions. The first start and repeated starting conditions are equivalent, functions.

Transmission data

Each byte placed on the SDA must be 8 -bit long, and the most effective (MSB) is first transmitted. The number of bytes that can be transmitted for each transmission is not restricted. There must be a confirmation position behind each byte of the data. Answer the related clock pulse is generated by the host. The transmitter releases the SDA cable (height) during the response period of the bell pulse. The receiver must be confirmed in the ninth clock pulse. The addressing receiver must be confirmed after receiving each byte.

After the startup condition, the I2C host sends a chip address. The length of this address is 7 bits, and the eighth bit is the data direction bit (R/W). LP3944 hard connecting lines 7 to 4, leaving 3 to 1 optional, as shown in Figure 6. For the eighth place, ""0"" is written, and ""1"" means reading. This LP3944 only supports writing during the chip addressing. The second byte selection of the data pointed to the register will be written. The third byte contains data to be written to the selected register.

Automatic growth

Automatic increase is a special feature supported by LP3944. It is used to eliminate duplicate chips and register addressing data in order When the register or reads data from the register. The automatic adding bit is in the address byte by the register, as shown in Figure 9. When the bit programming is ""1"