lm4510sdx National Semiconductor Corporation, lm4510sdx Datasheet - Page 13

• Manufacturer Part Number: lm4510sdx
• Description: Synchronous Step-up Dc/dc Converter With True Shutdown Isolation
• Manufacturer: National Semiconductor Corporation

The output capacitor should be capable of handling the RMS
current.
The ESR and ESL of the output capacitor directly control the
output ripple. Use capacitors with low ESR and ESL at the
SOFT-START FUNCTION AND SOFT-START
CAPACITOR SELECTION
The LM4510 has a soft-start pin that can be used to limit the
input inrush current. Connect a capacitor from SS pin to GND
to set the soft-start period. Figure 6 describes the soft start
process.
•
•
During the initial charging period, the required load current
must be smaller than the initial charge current to ensure
V
4.7 µF for C
10 µF for C
OUT
Initial charging period: When the device is turned on, the
control circuitry linearly regulating initial charge current
charges V
Soft-start period: After V
device starts switching and the C
current of 11 μA, ramping up to V
V
soft-start period ends after C
SS
reaches V
reaches V
C2012X5R0J475K
12103D106KAT2A
FIGURE 6. Soft Start Timing Diagram
GRM21BR60J475
TMK316BJ106KL
C2012X5R0J475
JMK212BJ475
OUT
IN
OUT
IN
Model
by limiting the inrush current.
FB
-0.7V (typ.).
. C
S
should be large enough to ensure
OUT
TABLE 3. Suggested C
reaches V
O
is fully charged.
IN
S
is charged at a constant
. This period ends when
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
IN
-0.7V (typ.), the
Type
30031023
IN
and C
Taiyo-Yuden
Taiyo-Yuden
OUT
Vendor
muRata
13
TDK
TDK
AVX
Capacitors and Their Suppliers
output for high efficiency and low ripple voltage. The output
capacitor also affects the soft-start time. See Soft-Start Func-
tion and Soft-Start Capacitor Selection. Table 3 shows sug-
gested input and output capacitors.
C
The soft-start time without load can be estimated as:
Where the I
on V
fuse current rating, make sure the value is higher than the
initial charging current.
COMPENSATION COMPONENT SELECTION
The LM4510 provides a compensation pin COMP to cus-
tomize the voltage loop feedback. It is recommended that a
series combination of R
sation network, as shown in the typical application circuit. In
addition, C
The series combination of R
pair according to the following equations:
In addition, C
equation:
Where R
proximately 1 MΩ, and amplifier voltage gain is typically 200
V/V depending on temperature and V
Refer to Table 4 for suggested soft start capacitor and com-
pensation components.
S
Selection
IN
and I
O
C2
Voltage Rating
is the output impedance of the error amplifier, ap-
SS_CHARGE
INIT_CHARGE
is used for compensating high frequency zeros.
C2
introduces a pole according to the following
6.3V
6.3V
6.3V
6.3V
25V
25V
(11 μA (typ.)). Also, when selecting the
is Initial Charging Current depending
C
and C
C
and C
C1
be used for the compen-
C1
IN
0805 (2012)
0805 (2012)
0805 (2012)
0603 (1608)
1206 (3216)
1210 (3225)
introduces a pole-zero
Inch (mm)
Case Size
.
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