1.0A Step-Down Switching Regulator
TC2575
Procedure (Adjustable Output Version: TC2575-ADJ) (Continued)
Procedure
Example
5. Output Capacitor Selection (COUT
)
5. Output Capacitor Selection (COUT
)
A.
12
A. Since the TC2575 is a forward–mode switching regulator
with voltage mode control, its open loop 2–pole–1–zero
frequency characteristic has the dominant pole–pair
determined by the output capacitor and inductor values.
COUT ≥ 7.785
= 53µF
8 x 220
To achieve an acceptable ripple voltage, select
OUT 100µF electrolytic capacitor.
C
For stable operation, the capacitor must satisfy the
following requirement:
VIN(max)
C
OUT ≥ 7.785
[µF]
VOUT x L [µF]
B. Capacitor values between 10µF and 2000µF will satisfy
the loop requirements for stable operation. To achieve an
acceptable output ripple voltage and transient response,
the output capacitor may need to be several times larger
than the above formula yields.
C. Due to the fact that the higher voltage electrolytic capaci-
tors generally have lower ESR (Equivalent Series
Resistance) numbers, the output capacitor’s voltage
rating should be at least 1.5 times greater than the output
voltage. For a 5.0V regulator, a rating of at least 8.0V is
appropriate, and a 10V or 16V rating is recommended.
Table 1. Inductor Selection Guide
Inductor Code
L100
Inductor Value
100µH
Pulse Eng
PE–92108
PE–53113
PE–52626
PE–52627
PE–53114
PE–52629
PE–53115
PE–53116
PE–53117
PE–53118
PE–53119
PE–53120
PE–53121
PE–53122
Renco
RL2444
RL1954
RL1953
RL1952
RL1951
RL1950
RL2445
RL2446
RL2447
RL1961
RL1960
RL1959
RL1958
RL2448
AIE
Tech 39
77 308 BV
77 358 BV
77 408 BV
77 458 BV
–
415–0930
415–0953
415–0922
415–0926
415–0927
415–0928
415–0936
430–0636
430–0635
430–0634
415–0935
415–0934
415–0933
415–0945
L150
150µH
L220
220µH
L330
330µH
L470
470µH
L680
680µH
77 508 BV
77 368 BV
77 410 BV
77 460 BV
–
H150
150µH
H220
220µH
H330
330µH
H470
470µH
H680
680µH
77 510 BV
77 558 BV
–
H1000
H1500
H2200
1000µH
1500µH
2200µH
77 610 BV
Note: *Contact Manufacturer
TC2575-1 3/13/00
10
TELCOM [ TELCOM SEMICONDUCTOR, INC ]
