TPS54040A_16 Datasheet, PDF (15/53 Pages) Texas Instruments – Step-Down DC-DC Converter

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TPS54040A
SLVSB58B – MARCH 2012 – REVISED JANUARY 2016
Feature Description (continued)
Another technique to add input voltage hysteresis is shown in Figure 28. 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.
TPS54040A
VIN
R1
I1
0.9 mA
Ihys
2.9 mA
R2
EN
+
1.25 V -
VOUT
R3
Figure 28. Adding Additional Hysteresis
R1 =
V_START - V_STOP
I_HYS
+
V_OUT
R3
(4)
R2 =
V_ENA
V_START - V_ENA
R1
+ I₁ -
V_ENA
R3
(5)
Do not place a low-impedance voltage source with greater than 5 V directly on the EN pin. Do not place a
capacitor directly on the EN pin if V_EN > 5 V when using a voltage divider to adjust the start and stop voltage.
The node voltage, (see Figure 29) must remain equal to or less than 5.8 V. The zener diode can sink up to 100
µA. The EN pin voltage can be greater than 5 V if the V_IN voltage source has a high impedance and does not
source more than 100 µA into the EN pin.
VIN
R1
ENA
R2
Node
10kohm
5.8V
Figure 29. Node Voltage
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