MIC28500 datasheet(21/29 Pages) MICREL

21 / 29 page

Micrel, Inc.

MIC28500

June 2011

M9999-060311-B

grease or thermal glue to make sure that the thermal

couple junction is making good contact with the case of

the IC. Omega brand thermal couple (5SC-TT-K-36-36)

is adequate for most applications.

Wherever

possible,

infrared

thermometer

recommended. The measurement spot size of most

infrared thermometers is too large for an accurate

reading on a small form factor ICs. However, a IR

thermometer from Optris has a 1mm spot size, which

makes it a good choice for measuring the hottest point

on the case. An optional stand makes it easy to hold the

beam on the IC for long periods of time.

External VIN Limiter Circuit

The external VIN limiter circuit can be implemented either

on EN pin or VDD pin. Only one of these VIN limiter

circuits is required. The external VIN limiter circuit limits

the minimum input to 30V. If the minimum input in

certain applications is more than 30V then neither of

these limiter circuits is needed. Enabling the device

below 30V VIN and under maximum loading could heat

up the device beyond safe operating conditions. The

following figures show the external VIN limiter circuit on

EN and VDD pins Figure 9A and Figure 9B respectively.

The VIN limiter on EN consists of D5, R22, D6, R23 and

VIN limiter on the VDD pin along with VDD supply

regulator consists of D4, R14, D2, and Q1.

Figure 9A: VIN Limiter On EN pin

Figure 9B: VIN Limiter On VDD pin

MIC28500 Datasheet(PDF) 21 Page - Micrel Semiconductor