TPS53015 Datasheet, PDF (8/19 Pages) Texas Instruments – Single Synchronous Step-down Controller for Low Voltage Power Rails

TPS53015
SLVSBF0A – JULY 2012 – REVISED AUGUST 2012
www.ti.com
OVER CURRENT PROTECTION
TPS53015 has a 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 R_DS(on) during the low-side driver on-time. If the
inductor current is larger than the over current limit (OCL), the TPS53015 delays the start of the next switching
cycle until the sensed inductor current falls below the OCL current. MOSFET R_DS(on) current sensing is used to
provide an accuracy and cost effective solution without external devices. To program the OCL, a resister should
be connected between DRVL and PGND. The recommended values are given inTable 1.
Table 1. OCL Resistor Values
Resister Value ( kΩ)
6.8
11
18
27
39
56
75
V_trip (V)
0.050
0.087
0.125
0.174
0.224
0.274
0.336
I_OCL is determined by Equation 2.
( ) ^æ
I_OCL = _ççè
V_IN -V_OUT
2×L×f_SW
×
V_OUT
V_IN
ö
÷÷ø ⁺
V_TRIP
R_DS(ON)
(2)
The trip voltage is set between 0.05V to 0.336V over all operational temperature, including the 4000ppm/°C
temperature slope compensation for the temperature dependency of the R_DS(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 TPS53015 will shut down.
OVER/UNDER VOLTAGE PROTECTION
TPS53015 monitors a resistor divided feedback voltage to detect over and under voltage. If the feedback voltage
is higher than 120% 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 68% of the reference voltage, the UVP comparator output goes high
and an internal UVP delay counter begins counting. After 1ms, TPS53015 latches OFF both top and bottom
MOSFET drivers. This function is enabled approximately 1.7 ms after power-on. The OVP and UVP latch off is
reset when EN goes low.
UVLO PROTECTION
TPS53015 has under voltage lock out protection (UVLO) that monitors the voltage of VREG5 pin. When the
VREG5 voltage is lower than UVLO threshold voltage, the device is shut off. All output drivers are OFF. The
UVLO is non-latch protection.
THERMAL SHUTDOWN
TPS53015 monitors its temperature. If the temperature exceeds the threshold value (typically 150°C), the device
shuts off. When the temperature falls below the threshold, the IC starts again. When VIN starts up and VREG5
output voltage is below its nominal value, the thermal shutdown threshold is kept lower than 150°C. As long as
VIN rises, T_J must be kept less than 110°C.
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