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HIGH RELIABILITY

DC/DC CONVERTER

HTA-SERIES

Description

n 150 to 250V DC Input Range

n Up to 20W Output Power

n Single and Dual Output Models Include

3.3, 5, 12, 15,

±5, ±12 and ±15V

n Internal EMI Filter

n Magnetically Coupled Feedback

n High Efficiency - to 76%

n -35°Cto+185°COperatingCaseTemperatureRange

n 10MΩ @ 500VDC Isolation

n Under-Voltage Lockout

n Short Circuit and Overload Protection

n Output Over Voltage Limiter

n Adjustable Output Voltage

n Synchronization Input and Output

n External Inhibit

n Low Weight, < 70grams

Features

200V Input, Single/Dual Output

Full environmental screening includes temperature cycling,

constant acceleration, fine and gross leak, and burn-in. Non-

screened versions of the HTA converters are available for

system development purposes. Variations in electrical

specifications and screening to meet custom requirements

can be accommodated.

Applications

n Down Hole Exploration Tools

The HTA Series of DC/DC converters is a family of 20W,

single and dual output, high reliability devices designed to

operate in extremely high temperature environments such as

those encountered in oil exploration applications. Features

include small size, low weight and high tolerance to

environmental stresses such as wide temperature extremes,

severe shock and vibration. All internal components are

derated to meet the intended operating environment.

Documentation including electrical stress and thermal analysis

are available.

The converters incorporate a fixed frequency single forward

topology with magnetic feedback and internal EMI filter. All

models include an external inhibit port and have an adjustable

output voltage. They are enclosed in a hermetic 1.5" x 4.0" x

0.430" AlSi package and weigh less than 70grams. The

package utilizes rugged ceramic feed-thru copper core pins

and is sealed using parallel seam welding.

03/03/09

The HTA series of converters utilize a single-ended forward

topology with resonant reset. The nominal switching frequency

is 500KHz. Electrical isolation and tight output regulation are

achieved through the use of a magnetically coupled feedback.

Voltage feed-forward with duty factor limiting provides high

line rejection and protection against output over voltage in the

event of an internal control loop failure. This mechanism

limits the maximum output voltage to approximately 20% over

the nominal regardless of the line voltage.

Output current is limited under any load fault condition to

approximately 125% of rated load at maximum operating case

temperature. An overload condition causes the converter

output to behave like a constant current source with the output

voltage dropping below nominal. The converter will resume

normal operation when the load current is reduced below the

current limit point. This protects the converter from both

overload and short circuit conditions.

The current limit point exhibits a slightly negative

temperature coefficient to reduce the possibility of

thermal runaway.

An external Inhibit port is provided to control converter

operation. The converter’s operation is inhibited when

this pin is pulled low. It is designed to be driven by an

open collector logic device. The pin may be left open

for normal operation and has a nominal open circuit

voltage of 4.0V with respect to the Input Return (pin 2).

The output voltage of all models can be adjusted using

a single external resistor.

Circuit Description

PD-97309A