SC1104BISTRT Semtech, SC1104BISTRT Datasheet - Page 8

• Manufacturer Part Number: SC1104BISTRT
• Description: IC, VOLTAGE MODE PWM CTRL, 7V, 8-SOIC
• Manufacturer: Semtech

Specifications of SC1104BISTRT

• 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: Lead free / RoHS 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