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5

HTB28XXS

(185°C, 28V Input, Single Output)

Technical Notes:

output by providing TTL compatible, positive logic signal to Inhibit pin (pin 3) and to Input Return (pin 2).

Inhibit signal is internally pulled “high” so that when not used, an open connection on the Enable pin permits

normal converter operation. A logical “low” on Inhibit pin will shut down the converter.

1. Inhibiting Converter Output:

2. Synchronization of Multiple Converters:

Sometimes there is a need to synchronize the HTB converters to an external frequency. For example if

several HTB converters have to be paralleled and operate off an external clock then this feature becomes

useful. This helps get rid of the “beat” frequency, thus relieving the problem of having to filter out a very low

frequency ripple. To accommodate this requirement, the HTB series of converters have a synchronization

input. The Sync Input port (pin 4) permits synchronization of a HTB converter to any compatible external

frequency source operating between 500 KHz and 600 KHz. This input signal should be referenced to the

Input Return and should have 10% to 90% duty cycle. Compatibility requires transition times to be less

than100ns, maximum low level of +0.8V and a minimum high level of +2.0V. When external synchronization

is not required, the Sync In pin should be left unconnected, thereby, permitting the converter to operate at its

sharing.

3. Mounting the HTB:

1. Check all surfaces for foreign material, burrs, or anything that may interfere with the different parts..

2. Apply a very thin layer of thermal grease to the mounting surface, aluminum or copper, which has

good thermal conductivity and surface flatness of 0.002" per inch. The thicker and wider the mounting

plate, the better the operating thermal equilibrium will be, thus improving overall reliability.

material between the converter and mounting surface.

4. Place the converter on the mounting surface and line it up with mounting holes.

5. Install screws using appropriate washers and tighten by hand (~6 in.oz) in the sequence shown below

in Figure 2. Please use 8-32 size screws and #8 flat washers.

6. Tighten the screws with appropriate torque driver using a controlled torque of 6 in.lb in the sequence as

shown in the diagram.

7. The case of the HTB converter is isolated from input or output return. It is optional for customer to decide

to either ground it or leave it floating. However, it is important to note that common mode capacitors are

internally tied to the case. Hence, connecting it to Ground (Earth) will enhance common mode noise

rejection/reduction.

It is important to mount the HTB converter on an aluminum plate or a heat sink before powering it up.

For this following procedure is recommended:

Figure 2. Top view of the HTB Converter with tightening sequence

Step 1

Step 2

Step 3

Step 4