lm4510sdx National Semiconductor Corporation, lm4510sdx Datasheet - Page 14

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

www.national.com
LAYOUT CONSIDERATIONS AND THERMAL
MANAGEMENT
High frequency switching regulators require very careful lay-
out of components in order to get stable operation and low
noise. All components must be as close as possible to the
LM4510 device. Refer to Figure 7 as an example. Some ad-
ditional guidelines to be observed:
1. C
rectly from VIN to PGND pins. This reduces copper trace
resistance, which affects the input voltage ripple of the device.
For additional input voltage filtering, typically a 0.1 uF bypass
capacitor can be placed between VIN and AGND. This by-
pass capacitor should be placed near the device closer than
C
2. C
ed directly from VOUT to PGND pins. Any copper trace
connections for the C
IN
.
OUT
IN
(R
(C
(C
must be placed close to the device and connected di-
C
must also be placed close to the device and connect-
) 9t06031A4642FBHFT
1
S
)TMK107SD222JA-T
) C1608C0G1E103J
FIGURE 7. Evaluation Board Layout
Model
OUT
capacitor can increase the series
TABLE 4. Suggested C
Ceramic, X5R
Ceramic, X5R
Resistor
Type
30031096
S
and Compensation Components
Yageo Corporation
Taiyo Yuden
14
Vendor
TDK
resistance, which directly affects output voltage ripple and
makes noise during output voltage sensing.
3. All voltage-sensing resistors (R
close to the FB pin to minimize copper trace connections that
can inject noise into the system. The ground connection for
the voltage-sensing resistor should be connected directly to
the AGND pin.
4. Trace connections made to the inductor should be mini-
mized to reduce power dissipation, EMI radiation and in-
crease overall efficiency. Also poor trace connection increas-
es the ripple of SW.
5. C
connected to AGND.
6. The AGND pin should connect directly to the ground. Not
connecting the AGND pin directly, as close to the chip as
possible, may affect the performance of the LM4510 and limit
its current driving capability. AGND and PGND should be
separate planes and should be connected at a single point.
7. For better thermal performance, DAP should be connected
to ground, but cannot be used as the primary ground con-
nection. The PC board land may be modified to a "dog bone"
shape to reduce LLP thermal impedance. For detail informa-
tion, refer to Application Note AN-1187.
FLASH/TORCH APPLICATION
LM4510 can be configured to drive white LEDs for the flash
and torch functions. The flash/torch can be set up with the
circuit shown in Figure 8 by using the resistor R
the current in Torch Mode and R
Flash Mode. The amount of current can be estimated using
the following equations:
S
, C
C1
, C
C2
, R
Voltage Rating
C
must be placed close to the device and
1/10W
6.3V
25V
F
to determine the current in
F1
, R
F2
) should be kept
603 (1608)
603 (1608)
603 (1608)
Case Size
Inch (mm)
T
to determine