LM43601_15 Datasheet, PDF (31/53 Pages) Texas Instruments – LM43601 SIMPLE SWITCHER® 3.5 V to 36 V 1 A Synchronous Step-Down Voltage Converter

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LM43601
SNVSA44A – AUGUST 2014 – REVISED AUGUST 2014
9.2.2.11 Under Voltage Lockout Set-Point
The undervoltage lockout (UVLO) is adjusted using the external voltage divider network of R_ENT and R_ENB. R_ENT
is connected between VIN and the EN pin of the LM43601 device. R_ENB is connected between the EN pin and
the GND pin. The UVLO has two thresholds, one for power up when the input voltage is rising and one for power
down or brown outs when the input voltage is falling. The following equation can be used to determine the VIN
(UVLO) level.
V_{IN-UVLO-RISING} = V_ENH × (R_ENB + R_ENT) / R_ENB
(24)
The EN rising threshold for LM43601 is set to be 2.1 V. Choose the value of RENB to be 1 MΩ to minimize input
current going into the converter. If the desired VIN (UVLO) level is at 5 V, then the value of R_ENT can be
calculated using the equation below:
R_ENT = (V_{IN-UVLO-RISING} / V_ENH - 1) × R_ENB
(25)
The above equation yields a value of 1.37 MΩ. The resulting falling UVLO threshold can be calculated as
follows:
V_{IN-UVLO-FALLING} = 1.8 × (R_ENB + R_ENT) / R_ENB
(26)
9.2.2.12 PGOOD
A typical pull-up resistor value is 10 kΩ to 100 kΩ from the PGOOD pin to a voltage no higher than 12 V. If it is
desired to pull up the PGOOD pin to a voltage higher than 12 V, a resistor can be added from the PGOOD pin to
ground to divide the voltage seen by the PGOOD pin to a value no higher than 12 V.
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