EK65

EK65U Rev D

3

REQUIRED COMPONENTS (NOT INCLUDED WITH KIT)

OPTIONAL COMPONENTS (NOT INCLUDED WITH KIT)

Reference

Function

Cin

Capacitor, Low ESR electrolytic, 100µF or greater with voltage rating greater then the

anticipated input voltage.

Cb1-4

Cboost capacitor, Low ESR electrolytic with voltage rating greater then the anticipated

boost voltage. Refer to the MP400FC data sheet for Cboost selection. One 120µF, 400V

electrolytic capacitor (Cb1) is supplied with the kit and is adequate for most applica-

tions. The value of Cboost is selected to meet required boost supply ripple voltage spec-

ifications for the application and to minimize switching noise on the boost supply.

Cboost will be as large as reasonably possible, in the range of 100µF to 500µF. An area

on the evaluation board large enough for 4 parallel 22mm diameter capacitors is pro-

vided. This allows maximum flexibility in the select of the capacitors for Cboost. Capaci-

tors with snap in terminals should still be soldered to the evaluation board to minimize

resistance.

Rset

Boost voltage programming resistor. Refer to the MP400FC data sheet for calculation of

Rset. Select a higher standard value resistor and use Rtrim (supplied) to calibrate the

boost voltage to the exact desired value. Alternatively, Rtrim can be used alone for a

fully adjustable boost supply.

Rcl

Operational amplifier current limit resistor. Refer to the MP400FC data sheet for selec-

tion of the current limit resistor.

Reference

Function

Lf

Boost supply filter inductor. The MP400FC includes a 47µH inductor in series with the

LFin pin and the +Vs supply of the high voltage op amp. This on board inductor forms a 2

pole LC filter with C1 and an on board parallel 0.1µF capacitor. Combined with a properly

selected Cboost, the high voltage DC boost voltage will be sufficiently clean for most

applications. However, an external inductor between Vboost and LFin, or Vboost and

+Vs can be used for additional filtering of the Boost supply voltage if necessary. Addi-

tional capacitance can be added to the filter between +Vs and AGND.

Cs, Rs

Also useful for boost supply filtering. These components form an RC snubber from drain

to source of the boost supply MOSFET switch. This snubber will help reduce or eliminate

overshoot and ringing of the MOSFET switch at switch turn-off that can appear on the

boost supply voltage. The component values shown on the schematic are adequate for

most applications but can be adjusted for your specific application. The power in the

resistor can be estimated by the formula PD = F*C*V2, where

F = 100 kHz

C = the value of Cs

V = the anticipated Vboost voltage.

Rs must be non-inductive. MP900 and MP9000 series resistors from Caddock Electron-

ics or equivalent resistors can be used.

Rs may require a heat sink such as Apex part number HS28 or HS23 (Not included).

Mounting holes for a heat sink are provided on the evaluation board that will accommo-

date either of these heat sinks.

Cc+, Cc-

High voltage op amp compensation capacitors. Refer to the MP400FC data sheet for

component selection.