TK112xxB
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 graphs below show 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
OUTPUT VOLTAGE RESPONSE
LOAD CURRENT STEP RESPONSE
(OFF→ON)
(OFF→ON)
C = 2.2 µF
L
I
= 5 to 35 mA
30 to 60 mA
I
= 10 mA, C = 1000 pF
N
LOAD
LOAD
C
= 0.01 µF
C
L
= 0.33 µF
N
0 to 30 mA
C
= 0.33 µF
L
C
= 1.0 µF
L
C
= 1.5 µF
L
C
= 0.1 µF
N
C
= 0.47 µF
L
I
= 30 mA
LOAD
400 600
TIME (µs)
-5
5
15
25
35
45
0
200
800
-5
5
15
25
35
45
TIME (µs)
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.
October 1999 TOKO, Inc.
Page 15
TOKO [ TOKO, INC ]
