May, 1997 TOKO, Inc.

Page 9

TK113xxB

DEFINITION AND EXPLANATION OF TECHNICAL TERMS (CONT.)

ON/OFF RESPONSE WITH CONTROL AND LOAD TRANSIENT RESPONSE

The turn on time depends upon the value of the output capacitor and the noise bypass capacitor. The turn on time will

increase with the value of either capacitor. The graph below shows the relationship between turn on time and load

capacitance. If the value of these capacitors is reduced, the load and line regulation will suffer and the noise voltage will

increase. If the value of these capacitors is increased, the turn on time will increase.

OUTPUT VOLTAGE RESPONSE

(OFF

→ON)

-5

5

15

35

ILOAD = 10 mA, CNP = 1000 pF

25

45

1.0 µF

1.5 µF

0.47 µF

CL = 0.33

LOAD CURRENT STEP

RESPONSE

-5

5

15

35

ILOAD

A = 0 to 30, B = 5 to 35, C = 30 to 60 mA

200 mV/DIV

25

45

B

C

A

CL = 0.33 µF

TIME (µS)

REDUCTION OF OUTPUT NOISE

Although the architecture of the Toko regulators is designed to minimize semiconductor noise, further reduction can be

achieved by the selection of external components. The obvious solution is to increase the size of the output capacitor.

A more effective solution would be to add a capacitor to the noise bypass terminal. The value of this capacitor should be

0.1

µf or higher (higher values provide greater noise reduction). Although stable operation is possible without the noise

bypass capacitor, this terminal has a high impedance and care should be taken to avoid a large circuit area on the printed

circuit board when the capacitor is not used. Please note that several parameters are affected by the value of the capacitors

and bench testing is recommended when deviating from standard values.

OUTPUT VOLTAGE RESPONSE

(OFF

→ON)

0

200

600

ILOAD = 30 mA, CL = 2.2 µF

400

800

CN = 0.1 µF

CN = 0.1 µF