TL284x, TL384x

CURRENT-MODE PWM CONTROLLERS

SLVS038E – JANUARY 1989 – REVISED DECEMBER 1999

10

POST OFFICE BOX 655303

APPLICATION INFORMATION

DEAD TIME

vs

TIMING CAPACITANCE

Figure 4

100

40

10

4

0

CT – Timing Capacitance – nF

100

40

10

4

1

0.4

0.1

VCC = 15 V

RT ≥ 5 kΩ

TA = 25°C

TIMING RESISTANCE

vs

FREQUENCY

Figure 5

100

1 k

10 k

100 k

1 M

f - Frequency - Hz

100

40

10

4

1

VCC = 15 V

TA = 25°C

CT = 22 nF

CT = 47 nF

CT = 100 nF

CT = 10 nF

CT = 4.7 nF

CT = 22 nF

CT = 1 nF

open-loop laboratory test fixture

In the open-loop laboratory test fixture shown in Figure 6, high peak currents associated with loads necessitate

careful grounding techniques. Timing and bypass capacitors should be connected close to the GND terminal

in a single-point ground. The transistor and 5-k

Ω potentiometer sample the oscillator waveform and apply an

adjustable ramp to the ISENSE terminal.

2N2222

4.7 k

Ω

1 k

Ω

Error Amplifier

Adjust

4.7 k

Ω

5 k

Ω

ISENSE

Adjust

RT

100 k

Ω

COMP

VFB

ISENSE

RT/CT

REF

OUTPUT

GND

VCC

0.1

µF

0.1

µF

REF

VCC

OUTPUT

GND

1 k

Ω, 1 W

A

CT

TL284x

TL384x

DUT

Figure 6. Open-Loop Laboratory Test Fixture