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TPS53127PW Fiches technique(PDF) 10 Page - Texas Instruments |
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TPS53127PW Fiches technique(HTML) 10 Page - Texas Instruments |
10 / 23 page V = TRIP (V-V ) IN O 2 1 · · L f SW ¾ · V O ¾ V IN · RDS(ON) I - OCL ( ) R (k )= TRIP W V (mV) TRIP I ( A) TRIP m ¾ TPS53127 SLVSA93 – MARCH 2010 www.ti.com Output Discharge Control TPS53127 discharges the outputs when ENx is low, or the controller is turned off by the protection functions (OVP, UVP, UVLO, and thermal shutdown). The device discharges output using an internal 40- Ω MOSFET which is connected to VOx and PGNDx. The external low-side MOSFET is not turned on during the output discharge operation to avoid the possibility of causing negative voltage at the output. This discharge ensures that on start the regulated voltage always initializes from 0 V. Over Current Limit TPS53127 has cycle-by-cycle over current limit feature. The over current limits the inductor valley current by monitoring the voltage drop across the low-side MOSFET RDS(ON) during the low-side driver on-time. If the inductor current is larger than the over current limit (OCL), the TPS53127 delays the start of the next switching cycle until the sensed inductor current falls below the OCL current. MOSFET RDS(ON) current sensing is used to provide an accuracy and cost effective solution without external devices. To program the OCL, the TRIP pin should be connected to GND through a trip voltage setting resistor, according to the following equations. (1) (2) The trip voltage should be between 30 mV to 300 mV over all operational temperature, including the 4000-ppm/°C temperature slope compensation for the temperature dependency of the RDS(ON). If the load current exceeds the over current limit, the voltage will begin to drop. If the over current conditions continues the output voltage will fall below the under voltage protection threshold and the TPS53127 will shut down. In an over current condition, the current to the load exceeds the current to the output capacitor; thus the output voltage tends to fall off. Eventually, it will end up with crossing the under voltage protection threshold and shutdown. Over/Under Voltage Protection TPS53127 monitors a resistor divided feedback voltage to detect over and under voltage. If the feedback voltage is higher than 115% of the reference voltage, the OVP comparator output goes high and the circuit latches the high-side MOSFET driver OFF and the low-side MOSFET driver ON. When the feedback voltage is lower than 70% of the reference voltage, the UVP comparator output goes high and an internal UVP delay counter begins counting. After 30 ms, TPS53127 latches OFF both top and bottom MOSFET drivers. This function is enabled approximately 1.7 x TSS after power-on. The OVP and UVP latch off is reset when EN goes low level. UVLO Protection TPS53127 has V5FILT under voltage lock out protection (UVLO) that monitors the voltage of V5FILT pin. When the V5FILT voltage is lower than UVLO threshold voltage, the device is shut off. All output drivers are OFF and output discharge is ON. The UVLO is non-latch protection. Thermal Shutdown The TPS53127 includes an over temperature protection shut-down feature. If the TPS53127 die temperature exceeds the OTP threshold (typically 150°C), both the high-side and low-side drivers are shut off, the output voltage discharge function is enabled and then the device is shut off until the die temperature drops. Thermal shutdown is a non-latch protection. 10 Submit Documentation Feedback Copyright © 2010, Texas Instruments Incorporated Product Folder Link(s): TPS53127 |
Numéro de pièce similaire - TPS53127PW |
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Description similaire - TPS53127PW |
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