參數(shù)資料
型號(hào): TPS51427ARHBR
廠商: TEXAS INSTRUMENTS INC
元件分類: 穩(wěn)壓器
英文描述: DUAL SWITCHING CONTROLLER, PQCC32
封裝: 5 X 5 MM, GREEN, PLASTIC, QFN-32
文件頁數(shù): 8/42頁
文件大?。?/td> 2131K
代理商: TPS51427ARHBR
OVERVOLTAGE/UNDERVOLTAGE PROTECTION
UNDERVOLTATGE LOCKOUT (UVLO) PROTECTION
THERMAL SHUTDOWN
SLUS843B – MAY 2008 – REVISED SEPTEMBER 2008 .................................................................................................................................................. www.ti.com
In an overcurrent condition, the current to the load exceeds the current to the output capacitor. As a result, the
output voltage tends to drop, and ends up crossing the undervoltage protection threshold, and the device shuts
down.
The TPS51427A also supports a cycle-by-cycle negative overcurrent limit in PWM-only mode. The negative
overcurrent limit is set to be negative, but at the same absolute value as the positive overcurrent limit. If the
output voltage continues to rise, the bottom MOSFET is always on; the inductor current reduces and reverse
direction after it reaches zero. When there is too much negative current in the inductor, the bottom MOSFET
turns off and a new on-time period is initiated; that is, the top MOSEFET turns on to allow current to flow into
VIN. After the on-time expires, the bottom MOSFET turns on again. This protection ensures a maximum
allowable discharge capability when the output voltage continues to rise, effectively reducing the possibility of the
overvoltage protection (OVP) circuitry.
The TPS51427A monitors the feedback voltage for Channel1 and output voltage for Channel2 to detect both
over- and undervoltage conditions. When the output voltage becomes 15% higher than the target value, the OVP
comparator output goes high after a 10-
s propagation delay; the circuit then latches the top MOSFET driver off
and the bottom MOSFET driver on, until the negative OCL limit is reached. At that time, the bottom MOSFET
turns off and the top MOSFET turns on for the minimum on-time. Once the minimum on-time expires, the bottom
MOSFET turns on again. This process repeats until the valley current of the inductor is above the negative
overcurrent limit. Once the inductor valley current is greater than the OCL, the bottom MOSFET remains on until
it is reset. Upon OVP activation, both PGOODx outputs are pulled low.
When the voltage becomes lower than 70% of the target voltage, the undervoltage protection (UVP) comparator
output goes high and an internal UVP delay counter begins counting. After 1 ms, the TPS51427A latches both
top and bottom MOSFETs off and shuts off the other channel as well. This function is enabled after the device
soft start completes.
The TPS51427A has V5FILT undervoltage lockout (UVLO) protection. When the V5FILT voltage is lower than
the UVLO threshold voltage, the TPS51427A shuts off. This feature is a non-latched protection circuit.
The TPS51427A monitors the temperature of the die itself. If the temperature exceeds the threshold value
(typically +140°C), the TPS51427A shuts down. This feature is a non-latched protection circuit.
16
Copyright 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS51427A
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