4-117

TELCOM SEMICONDUCTOR, INC.

7

6

5

4

3

1

2

8

BICMOS PWM CONTROLLERS

TC25C25

TC35C25

The 5k potentiometer sets a reference voltage at pin 2.

When ramp voltage of pin 5 reaches this reference voltage,

output drive pulse is active ON. Varying the discharge

resistor will vary the dead time. Increasing the discharge

resistor will effect an increase in the dead time.

BENCH TEST OPERATIONAL SIMULATION

WAVEFORMS

3V

OSC OUT

PIN 4

PIN 2

VOLTAGE

DEAD TIME

0.5V

CT

PIN 5

OUTPUT A

PIN 11

OUTPUT B

PIN 14

REPLACING BIPOLAR VERSIONS WITH CMOS

Although the pin-out and functions are the same for both

the Bipolar and CMOS versions, there are several differ-

ences that need to be taken into account. The reference

voltage on the TC35C25 is 4V instead of 5V and the

different for any particular frequency and dead-time require-

ment.

The most important difference is that the absolute

is 18V, whereas the UC3525 is 40V.

8

1

14

2

13

3

12

4

11

5

10

6

9

7

15

16

VDD

OUTB

VIN

VREF

GND

OUTA

SHDN

CMPTR

OSC OUT

SYNC

IN+

IN–

CT

RT

DISCH

SOFT

+

–

1000pF

MET

0 to 1k

MET

.1

µf

V011

16V

GND

GND

TYPICAL CHARACTERISTICS

0

5

10

15

20

25

30

35

40

1

0.8

0.6

0.4

0.2

0

Supply Current

vs. Frequency

CL = 2200pF

CL = 1000pF

CL = 470pF

CL = 10pF

VDD = 16V, TA +25°C

FREQUENCY (MHz)

Oscillator Frequency

vs. Ct and Rt

0

100

200

300

400

500

600

700

800

900

1000

800

600

400

200

Ct (pF)

Rt = 1k

Rt = 2k

Rt = 5k

Rt = 10k

Rt = 20k

VDD = VIN = 16V, TA +25°C

0

200

400

600

800

1000

3000

2500

2000

1500

1000

500

0

Dead Time

vs. Ct and Discharge Resistor

DISCHARGE RESISTOR (

Ω)

Ct = 1000pF

Ct = 500pF

Ct = 330pF

Ct = 100pF

VDD = 16V, TA +25°C, Rt = 10k