TK111xxM
APPLICATION INFORMATION
INPUT-OUTPUT CAPACITORS
Linear regulators require an output capacitor in order to maintain regulator loop stability. This capacitor should be selected
to ensure stable operation over the desired temperature and load range. The graphs below show the effects of
capacitance value and Equivalent Series Resistance (ESR) on the stable operation area.
111xx
CL
ESR
C
L
= 1
µF
C
L
= 2.2
µF
C
L
= 3.3
µF
C
L
= 10
µF
1000
1000
1000
1000
100
100
100
100
ESR (Ω)
ESR (Ω)
ESR (Ω)
10
STABLE
OPERATION
AREA
1
STABLE
OPERATION
AREA
1
STABLE
OPERATION
AREA
1
ESR (Ω)
10
10
10
STABLE
OPERATION
AREA
1
0.1
0.1
0.1
0.1
0 .01
1
50
IOUT (mA)
100
130
0 .01
1
50
IOUT (mA)
100
130
0 .01
1
50
IOUT (mA)
100
130
0 .01
1
50
IOUT (mA)
100
130
In general, the capacitor should be at least 1
µF
(aluminum electrolytic) and be rated for the actual ambient operating
temperature range. The table below shows typical characteristics for several types and values of capacitance. Please
note that the ESR varies widely depending upon manufacturer, type, size, and material.
ESR
Capacitance
1.0
µF
2.2
µF
3.3
µF
10
µF
Aluminum
Capacitor
2.4
Ω
2.0
Ω
4.6
Ω
1.4
Ω
Tantalum
Capacitor
2.3
Ω
1.9
Ω
1.0
Ω
0.5
Ω
Ceramic
Capacitor
0.140
Ω
0.059
Ω
0.049
Ω
0.025
Ω
Note: ESR is measured at 10 kHz.
Page 12
March 1999 TOKO, Inc.
TOKO [ TOKO, INC ]
