Datasheet

VSENSE
V
O
+
-
R1
R2
0.8 V
TPS57112-Q1
EN
I
1
I
hys
VIN
TPS57112-Q1
+
-
R1
R2
1.6 mA
1.6 mA
1
æ ö
-
ç ÷
è ø
æ ö
- +
ç ÷
è ø
ENFALLING
START STOP
ENRISING
ENFALLING
1 hys
ENRISING
V
V V
V
R1 =
V
I I
V
( )
´
- + +
ENFALLING
STOP ENFALLING 1 hys
R1 V
R2 =
V V R1 I I
TPS57112-Q1
www.ti.com SLVSAL8 –DECEMBER 2010
Figure 21. Voltage Divider Circuit
ENABLE AND ADJUSTING UNDER-VOLTAGE LOCKOUT
The TPS57112-Q1 is disabled when the VIN pin voltage falls below 2.6 V. If an application requires a higher
under-voltage lockout (UVLO), use the EN pin as shown in Figure 22 to adjust the input voltage UVLO by using
two external resistors. It is recommended to use the EN resistors to set the UVLO falling threshold (V
STOP
) above
2.6 V. The rising threshold (V
START
) should be set to provide enough hysteresis to allow for any input supply
variations. The EN pin has an internal pull-up current source that provides the default condition of the
TPS57112-Q1 operating when the EN pin floats. Once the EN pin voltage exceeds 1.25 V, an additional 1.6 mA
of hysteresis is added. When the EN pin is pulled below 1.18 V, the 1.6 mA is removed. This additional current
facilitates input voltage hysteresis.
Figure 22. Adjustable Undervoltage Lock Out
(2)
vertical spacer
(3)
Where I
hys
= 1.6 µA, I
1
= 1.6 µA, V
ENRISING
= 1.25 V, V
ENFALLING
= 1.18 V
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Product Folder Link(s): TPS57112-Q1