TPS61196PWPT

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1. Describe

TPS61196PWPT  provides a highly integrated solution For LCD TV backlighting with independent PWM Dimming function for each string. The device is a Current-Mode Boost Controller Drives Up to Six WLEDs Strings have multiple LEDs connected in series. Every string has Provides independent current regulators for LEDs Current adjustable from 50 mA to 400 mA ±1.5% matching accuracy. at the minimum voltage Current sink programmable from 0.3 V to 1 V to accommodate different LED current settings. enter The device has a voltage range of 8 V to 30 V. The device adjusts the output of the boost controller Voltage automatically provides only voltage Required by the LED string with maximum forward Voltage drop plus the minimum voltage required IFB pin for this string, thus optimizing the driver efficiency. Its switching frequency is programmed by An external resistor from 100 kHz to 800 kHz. TPS61196 supports direct PWM brightness Dimming. Independent PWM for each string Control input. During PWM dimming, the LED the frequency at which the current turns on or off and Duty cycle is determined externally pulse width modulated signal. The PWM frequency range is 90 Hz to 22 kHz. The device integrates overcurrent protection, output Short circuit protection, ISET short circuit to ground protection, diode open and short circuit protection, LED Open and short circuit protection, and overheating Shut down the circuit. Additionally, the TPS61196 can Detects IFB pin short to ground to protect LED String. The device also provides programmable inputs Undervoltage lockout threshold and output overvoltage protection threshold. TPS61196 has built-in linear regulator Step down the input voltage to the VDD voltage supply power to the internal circuits. The soft start circuit is Internal implementation to work with external capacitor to adjust the soft-start time to minimize Inrush current during boost converter startup. The device is available in a 28-pin HTSSOP package with PowerPAD™.

2. Feature

    1. 8V to 30V input voltage

    2. Output voltage up to 120V

    3. 100KHz to 800kHz programmable switching frequency

    4. Adaptive boost output for LED voltage

    5. Six current sinks, 200-mA continuous output, 400-mA pulse output per string

    6. ±1.5% current matching between strings

    7. High precision PWM dimming resolution up to 5000:1

    8. Programmable overvoltage thresholds for output and each sink current

    9. Input-programmable undervoltage threshold with adjustable hysteresis

  10. Adjustable soft-start time independent of dimming duty cycle

  11. Built-in LED open circuit and LED short circuit protection

  12. Built-in Schottky diode open/short protection

  13. Built-in ISET short circuit protection

  14. Built-in IFB short circuit protection

  15. Thermal shutdown

3. Application

    1. LCD TV backlight

    2. Scan mode LCD TV backlight

4. Pin configuration

5. Pin Description

6. Application Information

When more LED strings are required in the application, the TPS61196 can work in master/slave mode. The TPS61196 can be set as slave device when the voltage at the FSW pin is below 0.5 V or above 3.5 V. The master TPS61196 has booster controller and outputs the power rail for all LED strings. The slave TPS61196 only works as a LED driver and feedbacks the required headroom voltage to the master by connecting the slave's COMP pin to the master's REF pin. The ISNS pin of the slave TPS61196 must be connected to ground. The slave's OVP pin voltage must be 3% higher than the voltage at the master's OVP pin. The slave device can combine all fault conditions happening on both master and slave devices by connecting the master's FAULT output to the FSW pin of the slave device. The slave’s FAULT pin outputs the indication signal for all fault conditions.

7. Feature Description

    1. Supply Voltage

        The TPS61196 has a built-in linear regulator to supply the device analog and logic circuitry. The VDD pin, output of the regulator, must be connected to a 1-µF bypass capacitor. VDD only has a current sourcing capability of 15 mA. VDD voltage is ready after the EN pin is pulled high.

    2. boost controller

        The TPS61196 regulates the output voltage through current-mode pulse-width modulation (PWM) control. The control circuit turns on an external switching FET at the beginning of each switching cycle. An input voltage is applied across the inductor and energy is stored as the inductor current rises. During this part of the switching cycle, the load current is provided by the output capacitor. When the inductor current rises to the threshold set by the error amplifier (EA) output, the switching FET turns off and the external Schottky diode conducts. Lean forward. The inductor transfers the stored energy to supplement the output capacitor and provide load current. This operation is repeated every switching cycle. The switching frequency is set by an external resistor. The duty cycle of the converter is determined by WM logic block, compares EA output and slope compensation current ramp. The feedback loop regulates the OVP pin to the reference voltage generated by the minimum voltage on the IFB pin. The output of the EA is connected to the COMP pin. An external RC compensation network must be connected to the COMP pin to optimize feedback loop stability and transient response. The TPS61196 continuously adjusts the boost output voltage to accommodate any changes in the LED forward voltage. If the boost controller cannot regulate the output voltage due to the minimum pulse width (ton(min) in electrical characteristics), the TPS61196 will enter pulse skipping mode. In this mode, the device keeps the power switch off for several switching cycles to prevent the output voltage from rising above the regulated voltage. This operation usually occurs under light load conditions or when the input voltage is higher than the output voltage.

    3. Enable and Undervoltage Lockout

        The TPS61196 enables soft-start when the EN pin voltage is above 1.8 V. Exceeding 1 V disables the device. Provides undervoltage lockout (UVLO) protection. When the VIN pin voltage falls below 6.5 V, the TPS61196 powers down. Once the voltage on the VIN pin is restored, the TPS61196 resumes operation with hysteresis (VVIN_HYS) above the UVLO threshold of the input falling voltage. If a higher UVLO voltage is required, use the UVLO pin to adjust the input UVLO threshold by using an external resistor divider. Once the voltage on the UVLO pin exceeds the 1.229-V threshold, the device powers up and a 3.9 µA hysteretic current source is added. The current source is removed when the voltage on the UVLO pin falls below 1.229 V. The resistors for R1, R2 and R5 can be determined from the desired VSTART and VSTOP by Equation 2. To avoid noise coupling, resistor dividers R1 and R2 must be placed close to the UVLO pin.