TPS54060-Q1 Datasheet, PDF (16/52 Pages) Texas Instruments – 0.5-A 60-V STEP-DOWN SWIFT™ DC/DC CONVERTER WITH Eco-mode™

TPS54060-Q1
SLVSA25A – JANUARY 2010 – REVISED MARCH 2011
DETAILED DESCRIPTION (continued)
R1 = R2
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æ Vout - 0.8V ö
çè _{0.8 V} ÷ø
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(1)
Enable and Adjusting Undervoltage Lockout
The TPS54060 is disabled when the VIN pin voltage falls below 2.5 V. If an application requires a higher
undervoltage lockout (UVLO), use the EN pin as shown in Figure 28 to adjust the input voltage UVLO by using
the two external resistors. Though it is not necessary to use the UVLO adjust registers, for operation it is highly
recommended to provide consistent power up behavior. The EN pin has an internal pull-up current source, I1, of
0.9μA that provides the default condition of the TPS54060 operating when the EN pin floats. Once the EN pin
voltage exceeds 1.25V, an additional 2.9μA of hysteresis, Ihys, is added. This additional current facilitates input
voltage hysteresis. Use Equation 2 to set the external hysteresis for the input voltage. Use Equation 3 to set the
input start voltage.
TPS54060
VIN
R1
I1
0.9 mA
Ihys
2.9 mA
R2
EN
+
1.25 V -
Figure 28. Adjustable Undervoltage Lockout (UVLO)
R1 = ^{VSTART - VSTOP}
I_HYS
(2)
R2 =
V_ENA
V_START - V_ENA
R1
+ I₁
(3)
Another technique to add input voltage hysteresis is shown in Figure 29. This method may be used, if the
resistance values are high from the previous method and a wider voltage hysteresis is needed. The resistor R3
sources additional hysteresis current into the EN pin.
TPS54060
VIN
R1
I1
0.9 mA
Ihys
2.9 mA
R2
EN
+
1.25 V -
VOUT
R3
Figure 29. Adding Additional Hysteresis
16
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