s External Connection
q Wiring condition is very important. Noise associated with wiring inductance may cause problems.
For minimizing inductance, it is recommended to design the thick and short pattern (between large current diodos, input/
output capacitors, and terminal 1,2.)Single-point grounding(as indicated)should be used for best results.
w When output voltage is not stable, it can be improved by attaching capacitor(from several nF to several dozens nF)to
external resistor R2.
e High switching speed and low forward voltage type schottky barrier diode should be recommended for the catch-diode D
because it affects the efficiency. Please select the diode which the current rating is at least 1.2 times greater than maximum
r The output ripple voltage is highly influenced by ESR(Equivalent Series Resistor)of output capacitor, and can be minimized
by selecting Low ESR capacitor.
t An inductor should not be operated beyond its maximum rated current so that it may not saturate.
s Thermal Protection Design
Internal power dissipation(P)of device is generally obtained by the following equation.
P=ISW(Average.) x VSATxD' + VIN(voltage between VIN to COM terminal) x Iq'(consumption current)
Step down type
D'(Duty)= –T–(–pT–e–roni–o–d–)= ––V–I–NV––V–O–+SA–VT–F+–V–F––
ISW(Average)= IO(Output current.)
Polarity inversion type
ISW(Average)= –––1––1–D–'–– x IO(Output current.)
VF : Forward voltage of the diode
When ambient temperature Ta and power dissipation PD(MAX)during operation are determined, use Cu plate which allows the
element to operate within the safety operation area specified by the derating curve. Insufficient radiation gives an unfavorable
influence to the normal operation and reliability of the device.