SC4210AIMSTR Semtech, SC4210AIMSTR Datasheet - Page 9

• Manufacturer Part Number: SC4210AIMSTR
• Manufacturer: Semtech

Specifications of SC4210AIMSTR

• Lead Free Status / RoHS Status: Not Compliant

An output capacitor is not required for stability. If one is
used, compensation is required. Assuming there is no
output cap present, only Ccomp will be used. Under this
condition, the non-dominant pole and both zero’s are
pushed well above the unity gain frequency. Using only a
Ccomp = 100pF without an output capacitor, the system
yields a PM of 78.5º with a unity gain frequency of 387kHz;
see Figure 9.
POWER MANAGEMENT
Applications Information (Cont.)
2004 Semtech Corp.
Figure 8.
Figure 9.
9
The pass transistor does add an additional pole to the
transfer function. Generally speaking, this parasitic non-
dominant pole is at frequencies well above the unity gain
frequency but should be considered when various types
of N-MOSFETs are available.
The purpose of the R
response, reduce overshoot, and to remove an unwanted
output ripple voltage if no load is applied to the output.
In a practical sense, it is chosen to bleed (drain) about
100µA - 150µA. The optimum value depends on the
input/output voltage ratio and the constraints on the
output ripple voltage. Simulation analysis and real life
circuit testing have shown very close correlation.
Following the procedure described above yields a stable
operation and excellent transient response over a wide
range of output capacitors: extra low-ESR “ceramics” and
“organics”, mid-ESR “polymers” and “tantalums”, low-
cost aluminum capacitors. Below in Table 1 are the
summarized results of choosing R
for the typical application circuit shown on Page 1.
T
V
est Conditions:
V
IN
(
O
m
= 3.3V, V
U
T
V
4
4
4
3
5
5
4
5
5
_
5
6
6
R
- p
2
3
0
1
5
5
P I
) p
P
L
E
C
OUT
O
U
0
2
3
1
1
1
T
= 1.8V, I
0
0
1
1 .
0
0
0
2
3
µ (
) F
0
0
0
0
BLEED
0 .
0 .
0 .
0 .
E
OUT
Table 1
0
0
0
0
1
S
5
3
2
1
1
0
1
R
-
= 6A/0.12A, S
is to improve the transient
-
-
-
-
-
-
-
-
1
(
0
0
0
5
2
0
0
0 .
0 .
0 .
0 .
0
)
0
0
0
0
5
3
2
2
COMP
R
C
O
SC4210A
2
2
2
2
2
2
8
2
and C
M
0
7 .
7 .
P
4
4
4
4
2
4
www.semtech.com
(
r
) K
= 0.3A/µs.
COMP
C
C
O
1
1
1
1
1
1
1
1
M
values
3
5
0
0
P
0
0
5
0
0
3
0
0
0
0
0
0
0
0
p (
) F