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L6919C датащи(PDF) 8 Page - STMicroelectronics |
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L6919C датащи(HTML) 8 Page - STMicroelectronics |
8 / 32 page L6919C 8/32 DEVICE DESCRIPTION The device is an integrated circuit realized in BCD technology. It provides complete control logic and protections for a high performance dual-phase step-down DC-DC converter optimized for microprocessor power supply. It is designed to drive N Channel MOSFETs in a dual-phase synchronous-rectified buck topology. A 180 deg phase shift is provided between the two phases allowing reduction in the input capacitor current ripple, reducing also the size and the losses. The output voltage of the converter can be precisely regulated, programming the VID pins, from 0.800V to 1.550V with 25mV binary steps, with a maximum tolerance of ±0.6% over temperature and line voltage variations. The device manages On-The-Fly VID Code changes stepping to the new configu- ration following the VID table with no need for external components. The device provides an average current- mode control with fast transient response. It includes a 200kHz free-running oscillator. The error amplifier fea- tures a 15V/ µs slew rate that permits high converter bandwidth for fast transient performances. Current infor- mation is read across the lower mosfets RdsON or across a sense resistor in fully differential mode. The current information corrects the PWM output in order to equalize the average current carried by each phase. Current sharing between the two phases is then limited at ±10% over static and dynamic conditions. The device protects against Over-Current, with an OC threshold for each phase, entering in constant current mode. Since the current is read across the low side mosfets, the constant current keeps constant the bottom of the inductors current triangular waveform. When an under voltage is detected the device latches and the FAULT pin is driven high. The device performs also Over-Voltage protection that disables immediately the device turning ON the lower driver and driving high the FAULT pin. OSCILLATOR The switching frequency is internally fixed to 200kHz. The internal oscillator generates the triangular waveform for the PWM charging and discharging with a constant current an internal capacitor. The current delivered to the oscillator is typically 17 µA (Fsw=200KHz) and may be varied using an external resistor (ROSC) connected between OSC pin and GND or Vcc. Since the OSC pin is maintained at fixed voltage (Typ. 1.235V), the frequency is varied proportionally to the current sunk (forced) from (into) the pin considering the internal gain of 12KHz/ µA. In particular connecting it to GND the frequency is increased (current is sunk from the pin), while connecting ROSC to Vcc=12V the frequency is reduced (current is forced into the pin), according to the following relationships: Note that forcing a 17 µA current into this pin, the device stops switching because no current is delivered to the oscillator. Figure 1. ROSC vs. Switching Frequency R OS C vs. GND: fS 200kH z 1.237 R OSC K Ω () ------------------------------ 12 kHz µA ----------- ⋅ + 200 kHz 14.82 10 6 ⋅ R OSC K Ω () ------------------------------ + == R OS C vs. 12V: fS 200 kHz 12 1.237 – R OSC K Ω () ------------------------------ 12 kHz µA ----------- ⋅ – 200kH z 12.918 10 7 ⋅ R OSC K Ω () -------------------------------- – == 0 1000 2000 3000 4000 5000 6000 7000 0 50 100 150 200 Frequency (KHz) 0 200 400 600 800 1000 200 300 400 500 600 Frequency (KHz) |
Аналогичный номер детали - L6919C |
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Аналогичное описание - L6919C |
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