ZSPM4022-06 Datasheet, PDF (27/38 Pages) List of Unclassifed Manufacturers – 12V/6A Synchronous DC/DC Buck Regulator

ZSPM4022-06
12V/6A Synchronous DC/DC Buck Regulator
The voltage rating of the capacitor should be twice the output voltage for a tantalum capacitor and 20% greater for
aluminum electrolytic or OS-CON capacitors. The output capacitor RMS current is calculated by equation (11):
I_{COU T (RMS)}

ΔI_L(PP)
12
(11)
The power dissipated in the output capacitor is
P  I  ESR _DISS(COUT)
2
C_OUT (RMS)
C_OUT
(12)
3.1.3. Input Capacitor Selection
The input capacitor for the power stage input V_IN should be selected for ripple current rating and voltage rating.
Tantalum input capacitors might fail when subjected to high inrush currents caused by turning the input supply on.
A tantalum input capacitor’s voltage rating should be at least two times the maximum input voltage to maximize
reliability. Aluminum electrolytic, OS-CON, and multilayer polymer-film capacitors can handle the higher inrush
currents without voltage de-rating. The input voltage ripple will primarily depend on the input capacitor’s ESR. The
peak input current is equal to the peak inductor current; therefore
ΔV_IN = I_L(pk) × C_ESR
(13)
The input capacitor must be rated for the input current ripple. The RMS value of input capacitor current is
determined at the maximum output current. Assuming the peak-to-peak inductor current ripple is low, then
I_CIN(RMS)  I_OUT(MAX ) D(1 D)
Where
D = duty cycle
(14)
The power dissipated in the input capacitor is
P_DISS(CIN) = I_CIN(RMS)2 × ESR_CIN
(15)
3.1.4. Ripple Injection
The V_FB ripple required for proper operation of the g_m amplifier and error comparator is 20mV to 100mV. However,
the output voltage ripple is generally designed as 1% to 2% of the output voltage. For a low output voltage, such
as a 1V, the output voltage ripple is only 10mV to 20mV, and the feedback voltage ripple is less than 20mV. If the
feedback voltage ripple is so small that the g_m amplifier and error comparator cannot sense it, then the
ZSPM4022-06 will lose control and the output voltage is not regulated. In order to have some amount of V_FB
ripple, a ripple injection method is applied for low output voltage ripple applications. (Also see section 3.1.5
regarding internal ripple injection.)
Data Sheet
August 29, 2013
© 2013 Zentrum Mikroelektronik Dresden AG — Rev. 1.00
All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the
prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice.
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