User's Guide
SNVA095B – February 2005 – Revised April 2013
AN-1343 LM2852 Evaluation Board (500kHz version)
1
Introduction
In this evaluation board for the LM2852Y, three output voltage options are available and all three come
with the same bill of materials. The board may be configured in multiple ways providing various enabling
schemes, split-rail operation and filtering options. The LM2852 is a 2A step-down buck converter
belonging to TI’s SIMPLE SYNCHRONOUS® family. The LM2852 input voltage can range from 2.85V to
5.5V. Output voltages are factory set from 0.8V to 3.3V in 100mV increments. On-chip type-three
compensation facilitates low component count power supply design. This evaluation board enables the
power supply designer to investigate various functional configurations.
2
PVIN and AVIN
The input voltage to the LM2852 is connected to two PVIN pins and an AVIN pin. PVIN is the supply
connected to the output power switches; AVIN powers the controller logic of the switcher. Since PVIN and
AVIN are dedicated pins on the chip, split rail operation is possible. For example, AVIN can be set to 5V
and PVIN to 3.3V. Jumper J1 on the evaluation board is used to short together the AVIN and PVIN board
inputs.
3
Enable (EN)
The LM2852 enable pin is internally pulled up so that the part is enabled anytime the input voltage
exceeds the UVLO threshold. The evaluation board includes an input for enable so the user may set the
voltage on the enable pin. Jumper J2 also may be used to short the enable pin to AVin. Resistor, Rp may
be used as a pull down resistor to set the enable input to low.
4
Cf and Rf
Components Cf and Rf may be used to low-pass-filter the AVIN input. Filtering AVIN may improve line and
load regulation by reducing interfering signals on AVIN. 10 Ω and 1 µF are typical filter components for
AVIN.
5
CIN and CINX
This evaluation board provides two capacitor footprints for the CIN function. The larger footprint holds the
bulk of the CIN capacitor, for example 47 µF. Additional high frequency filtering may also be accomplished
by adding a smaller capacitor – CINX. A 1 µF or 100 nF capacitor is commonly used for high frequency
filtering.
6
CSS
The soft-start capacitor is used to control the start up behavior of the switching regulator. A 2.7 nF
capacitor yields approximately a 3 ms start up time.
7
Output Filter - L1, CO1 and CO2
Since the LM2852 uses on-chip compensation, the output filter component values must be restricted to a
certain range. The data sheet includes a table and information on component selection. Generally, the
output capacitors must have ESR values commonly found in Tantalum and non-Tantalum solution,
Niobium Oxide capacitors.
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SNVA095B – February 2005 – Revised April 2013
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AN-1343 LM2852 Evaluation Board (500kHz version)
Copyright © 2005–2013, Texas Instruments Incorporated
1
Board Schematic
8
www.ti.com
Board Schematic
U1
Cf
Rf
AVIN
1
2
J2
EN
J1
3
4
RP
CSS
5
6
PVIN
CIN
7
CINX
AVIN
SNS
EN
NC
SGND
NC
SS
PGND
NC
PGND
PVIN
PVIN
SW
14
13
12
11
10
9
SW
L1
8
VOUT
C
+ O2
C
+ O1
GND
Table 1. Bill of Materials
2
ID
Part Number
Type
Size
U1
LM2852, LM2852 or LM2852
2A Buck
HTSSOP-14
L1
DO3316P-153
Inductor
CO1
NOSD107M006R0100
Capacitor
Parameters
Qty
Vendor
1
TI
15 µH
1
Coilcraft
100 µF
1
AVX
CO2
Not Populated
CIN
GRM32ER60J476ME20B
Capacitor
1210
47µF/X5R/6.3V
0
1
Murata
CINX
GRM21BR71C105KA01B
Capacitor
0805
1µF/X7R/16V
1
Murata
CSS
VJ0805Y272KXXA
Capacitor
0805
2.7nF/X7R/25V
1
Vishay-Vitramon
Rf
CRCW060310R0F
Resistor
0603
10Ω ±10%
1
Vishay-Dale
Cf
GRM21BR71C105KA01B
Capacitor
0805
1µF/X7R/16V
1
Murata
J1
CRCW06030R0F
Resistor
0603
0Ω
1
Vishay-Dale
J2
Not Populated
0
RP
Not Populated
0
AN-1343 LM2852 Evaluation Board (500kHz version)
SNVA095B – February 2005 – Revised April 2013
Submit Documentation Feedback
Copyright © 2005–2013, Texas Instruments Incorporated
PCB Layouts
www.ti.com
9
PCB Layouts
Figure 1. Top Layer
Figure 2. Bottom Layer
96
PVIN = 3.3V
EFFICIENCY (%)
94
92
90
PVIN = 5.0V
88
86
84
0.1
1.0
10
ILOAD (A)
Figure 3. Typical Efficiency for 2.5V Output
SNVA095B – February 2005 – Revised April 2013
Submit Documentation Feedback
AN-1343 LM2852 Evaluation Board (500kHz version)
Copyright © 2005–2013, Texas Instruments Incorporated
3
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