(MOSFET ON Time)

Duty Cycle (%)

100

(MOSFET ON Time Body Diode ON Time)

u

LM74670-Q1

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SNOSD08A – SEPTEMBER 2015 – REVISED OCTOBER 2015

Device Functional Modes (continued)

(5)

7.4.2 Startup Voltage

The LM74670-Q1 will not initiate the charge pump operation if a closed loop system is in standby mode or the

drain current is smaller than 1mA (typical). This is due to a minimum body diode voltage requirement of the

LM74670-Q1 controller. If the drain current is too small to produce a minimum voltage drop of 0.48V at 25

ͦC, the

charge pump circuitry will remain off and the MOSFET will act just like a diode. It is very important to know the

body diode voltage parameter of a MOSFET before implementing it into the Smart Diode solution. Some N-

channels MOSFETs have very low body diode voltage at higher temperature. This makes their drain current

requirement higher to achieve 0.48V across the body diode in order to initiate the LM74670-Q1 controller at

higher temperatures.

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