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TPS54332DDAR Datasheet(PDF) 7 Page - Texas Instruments |
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TPS54332DDAR Datasheet(HTML) 7 Page - Texas Instruments |
7 / 26 page TPS54332 www.ti.com SLVS875B – JANUARY 2009 – REVISED FEBRUARY 2012 TYPICAL CHARACTERISTICS (continued) OVERVIEW The TPS54332 is a 28 V, 3.5 A, step-down (buck) converter with an integrated high-side n-channel MOSFET. To improve performance during line and load transients, the device implements a constant frequency, current mode control which reduces output capacitance and simplifies external frequency compensation design. The TPS54332 has a pre-set switching frequency of 1MHz. The TPS54332 needs a minimum input voltage of 3.5V to operate normally. The EN pin has an internal pull-up current source that can be used to adjust the input voltage under-voltage lockout (UVLO) with two external resistors. In addition, the pull-up current provides a default condition when the EN pin is floating for the device to operate. The operating current is 82 μA typically when not switching and under no load. When the device is disabled, the supply current is 1 μA typically. The integrated 80 m Ω high-side MOSFET allows for high efficiency power supply designs with continuous output currents up to 3.5 A. The TPS54332 reduces the external component count by integrating the boot recharge diode. The bias voltage for the integrated high-side MOSFET is supplied by an external capacitor on the BOOT to PH pin. The boot capacitor voltage is monitored by an UVLO circuit and will turn the high-side MOSFET off when the voltage falls below a preset threshold of 2.1 V typically. The output voltage can be stepped down to as low as the reference voltage. By adding an external capacitor, the slow start time of the TPS54332 can be adjustable which enables flexible output filter selection. To improve the efficiency at light load conditions, the TPS54332 enters a special pulse skipping Eco-modeTM when the peak inductor current drops below 160mA typically. The frequency foldback reduces the switching frequency during startup and over current conditions to help control the inductor current. The thermal shut down gives the additional protection under fault conditions. DETAILED DESCRIPTION FIXED FREQUENCY PWM CONTROL The TPS54332 uses a fixed frequency, peak current mode control. The internal switching frequency of the TPS54332 is fixed at 1 MHz. Eco-mode TM The TPS54332 is designed to operate in pulse skipping Eco-modeTM at light load currents to boost light load efficiency. When the peak inductor current is lower than 160 mA typically, the COMP pin voltage falls to 0.5V typically and the device enters Eco-modeTM . When the device is in Eco-modeTM, the COMP pin voltage is clamped at 0.5V internally which prevents the high side integrated MOSFET from switching. The peak inductor current must rise above 160mA for the COMP pin voltage to rise above 0.5V and exit Eco-modeTM. Since the integrated current comparator catches the peak inductor current only, the average load current entering Eco- modeTM varies with the applications and external output filters. VOLTAGE REFERENCE (Vref) The voltage reference system produces a ±2% initial accuracy voltage reference (±3.5% over temperature) by scaling the output of a temperature stable bandgap circuit. The typical voltage reference is designed at 0.8V. BOOTSTRAP VOLTAGE (BOOT) The TPS54332 has an integrated boot regulator and requires a 0.1 μF ceramic capacitor between the BOOT and PH pin to provide the gate drive voltage for the high-side MOSFET. A ceramic capacitor with an X7R or X5R grade dielectric is recommended because of the stable characteristics over temperature and voltage. To improve drop out, the TPS54332 is designed to operate at 100% duty cycle as long as the BOOT to PH pin voltage is greater than 2.1V typically. Copyright © 2009–2012, Texas Instruments Incorporated Submit Documentation Feedback 7 Product Folder Link(s): TPS54332 |
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