MP400FCU

MP400FC

P r o d u c t I n n o v a t i o n F r o m

tYpical application

The MP400FC is ideally suited to driv-

ing both piezo actuation and deflection

applications off of a single low voltage

supply. The circuit above boosts a sys-

tem 24V buss to 350V to drive an ink jet

print head. The MP400FCs high speed

deflection amplifier is biased for single

supply operation by external resistors R2

– R6, so that a 0 to 5V DAC can be used

as the input to the amplifier to drive the

print head from 0 to >300V.

General

Please read Application Note 1 “General

Operating Considerations” which covers

stability, power supplies, heat sinking, mounting, current limit, SOA interpretation, and specification interpretation.

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current limit

For proper operation, the current limit resistor, Rlim, must be connected

as shown in the external connections diagram. The minimum value

is 3.5Ω, however for maximum reliability and protection, the resistor

should be set as high as possible. The value of the resistor is calcu-

lated as follows, with Ilim in A; the maximum practical value is 30Ω.

Rlim = 0.7 / Ilim

saFe operatinG area

The MOSFET output stage of the MP400FC amplifier is not limited by

second breakdown considerations as in bipolar output stages. Only

thermal considerations and current handling capabilities limit the SOA.

The output stage is protected against transient flyback by the parasitic

body diodes of the output stage MOSFET structure. However, for pro-

tection against sustained high energy flyback external fast-recovery

diodes must be used..

supplY current

The MP400FC features a class A/B driver stage to drive the output

MOSFETs and an innovative input stage to achieve very high slew

rates. The supply current drawn by the MP400FC, even with no load,

varies with the slew rate of the output signal as shown in the graph

below.

stabilitY

The MP400FC is externally compensated and performance can be

tailored to the application. Use the graphs of small signal response

and power response as a guide. The compensation capacitor C

be rated at 500V working voltage. NPO capacitors are recommended.

The compensation capacitors must be mounted closely to the amplifier

pins 36 & 37 and 38 & 42 to avoid spurious oscillation.