Datasheet

+
-
-+
V
IN
I
UVLO
R13
R25
8
23 PA
i
X
+
-
-+
V
IN
I
UVLO
R13
R25
8
23 PA
i
X
V
IN
I
UVLO
V
HYST
t
V
UVLO_UP
V
UVLO_DOWN
www.ti.com Board Features
Figure 9. UVLO Circuit During Start-Up
The UVLO threshold and hysteresis can be programmed completely independent of each other. UVLO
hysteresis is accomplished with an internal 23 µA current source that is switched on and off into the
impedance of the UVLO set-point resistor divider. When the UVLO pin exceeds 1.24V, the current source
is activated to instantly raise the voltage at the UVLO pin. When the UVLO pin voltage falls below the
1.24V threshold, the current source is turned off, causing the voltage at the UVLO pin to fall. The UVLO
hysteresis range can be user adjusted using the gain resistor R26.
Figure 10. UVLO Circuit During Normal Operation
11
SNVA376A–December 2008–Revised May 2013 AN-1907 LM3423 Buck-Boost Configuration Evaluation Board
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