NR110K Datasheet, PDF (7/13 Pages) Sanken electric – Light Load High Efficiency, 31V, Buck Regulator

Light Load High Efficiency, 31V, Buck Regulator
NR110K series
Dec./24/2015
External Components Design Guide
(1)Diode D1
・The schottky-barrier diode must be used for D1. If other diodes like fast recovery diodes are used, IC may be
damaged because of the reverse voltage applied by the recovery voltage or ON voltage.
(2)Choke coil L1
・If the winding resistance of the choke coil is too high, the efficiency may go down to the extent that it is out of the rating.
・As the start current of the over current protection is approximately 4A, attention must be paid to the heating of the choke
coil by the magnetic saturation due to overload or short-circulated load.
(3)Capacitor C1( C2), C4(C5), C7
・As large ripple current across C1 (C2) and C4 (C5), capacitors with high frequency and low impedance for SMPS must be
used. Especially when the impedance of C4 (C5) is high, the switching waveform may not be normal at low temperature.
・C7 is a capacitor for soft start. A soft-start controls the over-shoot of the output voltage rising and rush current.
(4)Resistor R1, R2
・R4, R5, R6 are resistor to the Output Voltage. I_ADJ is required to set to 0.2mA.
R4, R5, R6 are calculated by the equation (1).
R4  R5  ^{VO  VFB}  ^{VO  0.8} ， R6  ^VFB  ^0.8 ≒4.0k
I _ADJ
0.2 10^3
IADJ _{0.2 10}3
------- (1)
In order to have optimum operating condition, each component must be connected with the minimum distance.
Rev.1.5
SANKEN ELECTRIC CO., LTD.
7
http://www.sanken-ele.co.jp