ZXRD1033NQ16TC 데이터 시트보기 (PDF) - Zetex => Diodes

부품명

상세내역

제조사

ZXRD1033NQ16TC

HIGH EFFICIENCY SIMPLESYNC PWM DC-DC CONTROLLERS

Zetex => Diodes 

ZXRD1000 SERIES

Optimising for Transient Response.

Transient response is important in applications where

the load current increases and decreases rapidly. To

optimise the system for good transient response

certain criteria have to be observed.

The optimum solution using the ZXRD series uses the

adjustable N phase controller in synchronous mode as

represented in the diagram opposite. The external

networks for this solution require the use of the

adjustable controller option.

By using standard ’bulk’ capacitors in parallel with a

single OS-CON capacitor significant performance

versus cost advantage can be given in this application.

The low ESR of the OS-CON capacitor provides

competitive output voltage ripple at low capacitance

values. The ’bulk’ capacitors aid transient response.

However, the low ESR of the OS-CON capacitor can

cause instability within the system. To maintain

stability an RC network (RX, Cx1 ) ha s t o be

implemented. Furthermore, a capacitor in parallel with

R6 (Cx2) is required to optimise transient response. To

do this the appropriate adjustable ZXRD must be used

because the input to the internal error amplifier (pin

16) has to be accessed. The adjustable device differs

from fixed controller versions in this respect. This

combined with a frequency compensation adjustment

gives an optimised solution for excellent transient

response.

Layout Issues

Layout is critical for the circuit to function in the most

efficient manner in terms of electrical efficiency,

thermal considerations and noise. The following

guidelines should be observed:

A 2.2µF (C8) decoupling capacitor should be as close

as possible to the drive MOSFETs and D1 anode. This

capacitor is effectively connected across VIN and GND

but should be as close as possible to the appropriate

components in either N or P, synchronous or

non-synchronous configurations. Furthermore the

GND connection of the synchronous MOSFET/D1 and

output capacitors should be close together and use

either a ground plane or at the very least a low

inductance PCB track.

For the standard application circuits, a Gerber file can

be made available for the layout which uses the

materials as listed in the bill of materials table for the

reference designs.

Reference Designs.

In the following section reference circuits are shown for

the ZXRD series in both synchronous and

non-synchronous modes. These are shown for each of

the N and P phase controllers. In each case efficiency

graphs are shown for the appropriate configuration

using 3.3V and 5V ZXRD devices. The BOM is then

shown for the design. Additional and alternative

components are shown with a ’*’. These refer to

modifications to the design to optimise for transient

response. Optimisation is reached using the adjustable

version of either N or P phase controller device.

10

ISSUE 4 - OCTOBER 2000

Share Link: