TK75002DIMG/75002 データシートの表示（PDF） - Toko America Inc

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TK75002DIMG/75002

ERROR SIGNAL ISOLATOR

Toko America Inc  

TK75002

APPLICATION INFORMATION (CONT.)

TEST CIRCUIT EXAMPLE

This simple circuit shown in Figure 7 is designed to allow

the user to probe and observe the characteristic

performance and behavior of either a TK75001 or a

TK75003 operating with a TK75002. Also, either IC can be

characterized independently in the circuit. The TK75001/

TK75003 are pulse width modulated (PWM) controllers.

The TK75002 is a pulse-amplitude-modulated (PAM)

controller.

In all of the following text, the TK75003 can be substituted

for the TK75001, depending on which of those two ICs is

used in the characterization circuit. Ground is common to

both the TK75001 and the TK75002.

VCC1 provides power to the TK75001. VCC1 must be brought

up to around 15 V to turn on the TK75001. Turn-on can be

determined by any of the following events: a) current from

the VCC1 supply jumps from ~ 1 mA to ~ 20 mA as the

supply voltage is raised, b) a timing waveform appears at

TP5, or c) a drive signal appears at TP6 (assuming that TP3

or TP4 is held low). TP5 is the timing pin of the TK75001,

which has a sawtooth voltage waveform across the 1000

pF timing capacitor. TP4 is the feedback pin. The user can

force a voltage there directly (for example, to measure the

threshold voltage of the PWM, VCCD, which is approximately

0.92 V) or voltage can be applied at TP3. Applying the

voltage at TP3 allows a voltage ramp to form and the PWM

characteristic to be observed. The modulation range from

zero to maximum PWM is approximately 0 to 1 V of voltage

applied to TP3. The higher the applied voltage, the narrower

the pulse width. Finally, in order to see the TK75001

operating with the TK75002, the voltage at TP3 can be

applied by causing the TK75002 to operate, as described

next.

VCC2 provides power to the TK75002. The TK75002 is

configured with a resistor-feedback limited DC gain from

VCC2 so that a gradual PAM change can be easily observed

as VCC2 is changed. The modulation range from zero to

maximum PAM is approximately 5 to 6 V of applied VCC2.

The higher the VCC the higher the PAM signal magnitude.

The PAM signal can be observed by probing TP2, although

it is more easily understood when connecting the probe

ground to VCC2 since PAM is with respect to the supply

voltage in the TK75002. The peak-rectified transformer-

coupled output of the TK75002 can be observed at TP3.

Page 8

January 1999 TOKO, Inc.

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