SC4501STDEVB Semtech, SC4501STDEVB Datasheet - Page 13

• Manufacturer Part Number: SC4501STDEVB
• Description: EVALUATION BOARD
• Manufacturer: Semtech

Specifications of SC4501STDEVB

• Silicon Manufacturer: Semtech
• Application Sub Type: Step Up Switching Regulator
• Kit Application Type: Power Management - Voltage Regulator
• Silicon Core Number: SC4501
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

with
Example: Increase the turn on voltage of a V
converter from 1.4V to 2.75V.
Using V
The resulting UVLO hysteresis is:
Application Information
POWER MANAGEMENT
2005 Semtech Corp.
R
V
HYS
3
V
L
Figure 7. Programmable Hysteretic UVLO Circuit
H
150
= 2.75V and R
I
1
HYS
4 .
R3
R4
K
R
V
3
.
.
4
SC4501
SHDN
6 .
3
A
4
1.1V
150
= 100K in (12),
6/8
IN
I HYS
4.6 A
K
+
-
SWITCH CLOSED
C6
Figure 8. Simplified Block Diagram of a Boost Converter
WHEN Y = “1”
V
IN
. 0
COMPARATOR
COMP
R3
69
C4
V
.
RO
IN
= 3.3V boost
Gm
Y
POWER
STAGE
REFERENCE
+
-
VOLTAGE
1.242V
FB
13
The turn off voltage is:
Frequency Compensation
Figure 8 shows the equivalent circuit of a boost converter
using the SC4501. The output filter capacitor and the load
form an output pole at frequency:
where C
equivalent load resistance.
The zero formed by C
(ESR) is neglected due to low ESR of the ceramic output
capacitor.
There is also a right half plane (RHP) zero at angular
frequency:
I
Figure 1(a) as an example,
OUT
z2
R
. Using the 5V to 12V boost regulator (1.35MHz) in
V
decreases with increasing duty cycle D and increasing
L
OUT
p
Z
C5
2
2
V
2
H
R
R1
R2
. 0
is the output capacitor and
OUT
V
I 2
5
OUT
74
V
V
HYS
OUT
1
ESR
L
C
I
C2
A
OUT
2
D
. 2
6
2
8 .
R OUT
75
2
R
and its equivalent series resistance
OUT
V OUT
2
. 0
C
2
69
. 2
06
V
R
1
OUT
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4 .
SC4501
V
.
V
I
OUT
OUT
is the
(13)
(14)