MC34167 MC33167

11

MOTOROLA ANALOG IC DEVICE DATA

Figure 24. Triple Output Converter

4

2

1

5

3

+

VO1

5.0 V/3.0 A

EA

Reference

Thermal

Oscillator

S

R

Q

PWM

UVLO

ILIMIT

Vin

24 V

1000

+

6.8 k

68 k

0.1

1N5825

+

1000

1000

+

1000

+

MUR110

MUR110

VO3

–12 V/200 mA

VO2

12 V/250 mA

T1

+

+

Tests

Conditions

Results

Line Regulation

5.0 V

12 V

–12 V

Vin = 15 V to 30 V, IO1 = 3.0 A, IO2 = 250 mA, IO3 = 200 mA

3.0 mV =

± 0.029%

572 mV =

± 2.4%

711 mV =

± 2.9%

Load Regulation

5.0 V

12 V

–12 V

Vin = 24 V, IO1 = 30 mA to 3.0 A, IO2 = 250 mA, IO3 = 200 mA

Vin = 24 V, IO1 = 3.0 A, IO2 = 100 mA to 250 mA, IO3 = 200 mA

Vin = 24 V, IO1 = 3.0 A, IO2 = 250 mA, IO3 = 75 mA to 200 mA

1.0 mV =

± 0.009%

409 mV =

±1.5%

528 mV =

± 2.0%

Output Ripple

5.0 V

12 V

–12 V

Vin = 24 V, IO1 = 3.0 A, IO2 = 250 mA, IO3 = 200 mA

75 mVpp

20 mVpp

20 mVpp

Short Circuit Current

5.0 V

12 V

–12 V

Vin = 24 V, RL = 0.1 Ω

6.5 A

2.7 A

2.2 A

Efficiency

TOTAL

Vin = 24 V, IO1 = 3.0 A, IO2 = 250 mA, IO3 = 200 mA

84.2%

# TURNS(SEC) +

VO(SEC) ) VF(SEC)

VO(PRI))VF(PRI)

#TURNS(PRI)

Multiple auxiliary outputs can easily be derived by winding secondaries on the main output inductor to form a transformer. The secondaries must be connected so

that the energy is delivered to the auxiliary outputs when the Switch Output turns off. During the OFF time, the voltage across the primary winding is regulated by

the feedback loop, yielding a constant Volts/Turn ratio. The number of turns for any given secondary voltage can be calculated by the following equation:

T1 = Primary: Coilcraft M1496–A or General Magnetics Technology GMT–0223, 42 turns of #16 AWG on Magnetics Inc. 58350–A2 core.

Heatsink = AAVID Engineering Inc. 5903B, or 5930B.

Note that the 12 V winding is stacked on top of the 5.0 V output. This reduces the number of secondary turns and improves lead regulation. For best auxiliary

regulation, the auxiliary outputs should be less than 33% of the total output power.