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Additional Application Circuits

Isolation

Amplifier

COMMUNICATION

(Programming & Status Reporting)

14

1

13

8

PVDD

VDD

CS

10

OUT2

3

4

2

5

6

IN1

AGND

3V3

IN2

CLF

7

UCD7201PWP

11

OUT1

9

PGND

12

NC

ILIM

NC

Bias Supply

Bias Winding

VIN

VOUT

DIGITAL

CONTROLLER

GND

PWMA

ADC4

INTERRUPT or CCR

PWMB

ADC3

VCC

PWM or GPIO

ADC1

ADC2

CS

XFMR

Gate Drive

Transformer

(3 winding)

15

16

14

2

4

14

1

13

8

PVDD

VDD

CS

10

OUT2

3

4

2

5

6

IN1

AGND

3V3

IN2

CLF

7

UCD7201

11

OUT1

9

PGND

12

NC

ILIM

NC

Bias Supply

Bias Winding

VIN

VOUT

13

UCC28089

GND

OUTA

OUTB

VDD

DIS

CS

3

1 SYNC

CT

UCD7201

SLUS645B – FEBRUARY 2005 – REVISED JULY 2005

Figure 2 shows the UCD7201 in a half-bridge converter design. The digital controller is performing the output

voltage compensation and all supervisory functions. The isolation amplifier is made up of a linear opto-coupler

configured for a gain of 1/10, so the output voltage is transformed to a level comparable with the ADC of the

digital controller.

Figure 2. Half-Bridge Converter

Figure 3 shows the UCD7201 in an analog only implementation of an intermediate bus converter. The ILIM pin of

the UCD7201 is exponentially increased at start-up, which minimizes overshoot on the output voltage. The

UCC28089 is a push-pull controller with fixed dead-time. The UCC28089 operates at a fixed duty cycle close to

100% so the circuit acts like a DC transformer linearly transforming the input voltage via the turns ratio of the

transformer.

Figure 3. Intermediate Bus Converter

10