SC1104BISTR Semtech, SC1104BISTR Datasheet - Page 8
SC1104BISTR
Manufacturer Part Number
SC1104BISTR
Description
IC, VOLTAGE MODE PWM CTRL, 7V, 8-SOIC
Manufacturer
Semtech
Datasheet
1.SC1104AISTRT.pdf
(14 pages)
Specifications of SC1104BISTR
Input Voltage
7V
Output Current
600mA
Frequency
600kHz
Supply Voltage Range
4.5V To 7V
Digital Ic Case Style
SOIC
No. Of Pins
8
Operating Temperature Range
-40°C To +85°C
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
Value for the resistor R
divider upper resistor R
Example.
Switching frequency f
Output capacitance C
Output capacitor ESR = 45m
Output inductance L
Input voltage V
Output voltage V
Let’s choose crossover frequency
f
The compensation values used in this example are based
on the following criteria:
f
Therefore,
Since, the EA can sink/source about 1mA, let’s choose
Rc = 680 , then
Assuming the output divider lower resistor R
for V
At the closed-loop crossover frequency f
Theory of Operation (Cont.)
©
POWER MANAGEMENT
CO
Z
= f
2006 Semtech Corp.
= 1/20
OUT
LC
; f
= 3.3V the R
NET
f
f
LC
ESR
= 1/10
f
SW
C
C
2
C
IN
2
P
N
C
= 15kHz
OUT
= 12V
f
NET
2
2
= 3.3V
OUT
2
A
OUT
SW
. 0
4.7µ
= 2.32k.
f
LC
= 4.7
N
A
015
2
= 300kHz
.
= 3 x 330
; f
1
1
should be 1/10 of the output
1
Fp
f
1
1
NET
H
Fz
P
µH
/each
990
= 10
Rc
990
1
Ra
Rc
Ra
F
F
1500
µF
Cn
0
0
1 .
10
3 .
f
CO
. 2
pF
.
F
72
F
33
= 150kHz
CO
, the
kHz
kHz
B
= 1k, then
8
attenuation due to the L
resistor divider R
the PWM modulator and the gain of the
transconductance error amplifier (Gm
Shown below is a typical Bode plot of the open-loop
frequency response of SC1104 based buck converter.
-40.0
-80.0
80.0
40.0
0
-50.0
-150
-250
-350
-450
1
1
vdberr
2
vpherr
10
A
, R
B
is compensated by the gain of
100
O
, C
frequency in hertz
O
filter and the output
1k
SC1104A/B
EA
10k
www.semtech.com
Z
COMP
100k
).
1Meg
2
1