ON/OFF

Q1

2N7000 or

equivalent

GND

DIM

BOOT

SW

CS

RON

LM3402/02HV

VIN

D1

L1

VCC

GND

DIM

BOOT

SW

CS

RON

LM3402/02HV

VIN

D1

L1

VCC

Z1

LM3402, LM3402HV

SNVS450E – SEPTEMBER 2006 – REVISED MAY 2013

www.ti.com

Figure 20. Output Open Circuit Protection

LOW POWER SHUTDOWN

level MOSFET as shown in Figure 21. Low power MOSFETs like the 2N7000, 2N3904, or equivalent are

recommended devices for putting the LM3402/02HV into low power shutdown. Logic gates can also be used to

shut down the LM3402/02HV as long as the logic low voltage is below the over temperature minimum threshold

of 0.3V. Noise filter circuitry on the RON pin can cause a few pulses with a longer on-time than normal after RON

is grounded or released. In these cases the OVP/OCP comparator will ensure that the peak inductor or LED

Figure 21. Low Power Shutdown

THERMAL SHUTDOWN

Internal thermal shutdown circuitry is provided to protect the IC in the event that the maximum junction

temperature is exceeded. The threshold for thermal shutdown is 165°C with a 25°C hysteresis (both values

typical). During thermal shutdown the MOSFET and driver are disabled.

14

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