FAN4868

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10

STARTUP

Operating Conditions

> 2.3

16

10

> 2.7

16

15

> 2.7

20

22

Transient Protection

To protect against external voltage transients caused by

ESD discharge events, or improper external connections,

some applications employ an external transient voltage

suppressor (TVS) and Schottky diode (D1 in Figure 19).

Figure 19. FAN4868 with External

Transient Protection

CIN

EN

SW

L1

GND

VIN

FB

VOUT

D1

Connector

C2

C1

B2

B1

A2

A1

1 μH

4.7 μF

2.2 μF

to +10 V or –2 V during external transient events. The

Schottky diode protects the output devices from the positive

excursion. The FB pin can tolerate up to 14 V of positive

excursion, while both the FB and VOUT pins can tolerate

negative voltages.

The FAN4868 includes a circuit to detect a missing or

about 0.7 V, the IC shuts down. The IC remains shut down

toggled.

response when the Schottky is used. When a load is applied

at the FB pin, the forward voltage of the D1 rapidly increases

before the regulator can respond or the inductor current can

change. This causes an immediate drop of up to 300 mV,

supplies instantaneous current to the load while the regulator

adjusts the inductor current. A value of at least half of the

needs to withstand the maximum voltage at the FB pin as the

TVS is clamping.

The maximum DC output current available is reduced

with this circuit, due to the additional dissipation of D1.

LAYOUT GUIDELINE

Figure 20. WLCSP Suggested Layout (Top View)