Texas Instruments LP2951EVM User Manual
User's Guide
SLVUAS6A–March 2017–Revised January 2018
LP2951EVM
Contents
1 Introduction ................................................................................................................... 2
2 HW Description .............................................................................................................. 2
3 Setup .......................................................................................................................... 6
4 Thermal Guidelines and Layout Recommendations .................................................................... 8
5 Board Layout ................................................................................................................. 9
6 EVM Schematic............................................................................................................. 10
7 Bill of Materials ............................................................................................................. 11
List of Figures
1 EVM With SON Package and SOIC Pads ............................................................................... 2
2 Input Capacitors C1-C
3 Output Capacitors C4-C
4 Location for Bypass Capacitor C
5 R1and R
6 Resistors R3-R
Used to Set Fixed Voltage Mode on EVM................................................................... 4
2
6
7 LP2951 Adjustable Output Voltage Block Diagram ..................................................................... 7
8 EVM With Adjustable Mode Resistors Populated ....................................................................... 8
9 LP2951EVM Board Layout................................................................................................. 9
10 LP2951EVM Schematic ................................................................................................... 10
...................................................................................................... 3
3
.................................................................................................... 3
7
......................................................................................... 4
8
Used to Set Output Voltage in Adjustable Voltage Mode ........................................... 5
1 Compatible Parts and Packages for LP2951EVM....................................................................... 2
2 Shutdown Jumper Position Versus Output............................................................................... 6
3 Bill of Materials ............................................................................................................. 11
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List of Tables
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LP2951EVM
1
Introduction
1 Introduction
The Texas Instruments LP2951EVM helps evaluate the operation and performance of the LP2951 family
of LDOs. The LP2951 family can accommodate a wide input supply-voltage range of up to 30 V.
2 HW Description
This section describes the hardware of the LP2951EVM.
2.1 LP2951 Device
The LP2951EVM comes populated with LP2951-50-Q1 in the SON package. However, this EVM can be
used to evaluate the SOIC package LP2951 device as well. Figure 1 shows the EVM populated with the
SON package and the pads for the SOIC package on the board. Table 1 shows all LP2951 part numbers
and packages that are compatible with the LP2951EVM.
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Figure 1. EVM With SON Package and SOIC Pads
Table 1. Compatible Parts and Packages for LP2951EVM
Part Number Packages
LP2951 SOIC (D)
LP2951-30 SOIC (D)
LP2951-33 SOIC (D), SON (DRG)
LP2951-33-Q1 SON (DRG)
LP2951-50 SOIC (D), SON (DRG)
LP2951-50-Q1 SOIC (D), SON (DRG)
LP2951-N SOIC (D)
2
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2.2 Input Capacitors
Capacitors C1-C3are all capacitors routed to the input of the LP2951 device to ground. C2comes
populated on the board, and has a value of 1 µF. C1and C3are pads that allow for additional input
capacitors to be put on the board and can accommodate different capacitor sizes.
HW Description
2.3 Output Capacitors
Capacitors C4-C7are all capacitors routed to the Output pin. C4-C6are ceramic caps routed in series with
a 1-Ω resistor, R7, from the output to ground. This series resistance helps stabilize the internal amplifier of
the LP2951 device. See the LP2951 or LP2951-N data sheet for the recommended series resistance
when using a ceramic output capacitor. C5comes populated on the board and has a value of 2.2 µF. C
and C6are pads that allow for additional output capacitors to be put on the board and can accommodate
different capacitor sizes. C7is meant for an electrolytic capacitor. It is routed directly from the output to
ground with no series resistance, but still functionally the same as C4-C6. Electrolytic Capacitors do not
require an external series resistance as the internal ESR of an electrolytic is typically enough to keep the
device stable.
Figure 2. Input Capacitors C1-C
3
4
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Figure 3. Output Capacitors C4-C
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LP2951EVM
3
HW Description
2.4 Bypass Capacitor
Capacitor C8is meant to give additional stability to the internal amplifier of the LP2951 device by placing
additional capacitance between the Output and the Feedback pins. Stray capacitance to the LP2951
Feedback pin can cause instability. This may especially be a problem when using high value external
resistors to set the output voltage. To fix this problem, populate C8with a 100-pF capacitor and increase
the output capacitor to at least 3.3 µF. See the LP2951 and LP2951-N data sheets for more information
regarding the Cbypass.
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Figure 4. Location for Bypass Capacitor C
2.5 Fixed Output Voltage Resistors
Resistors R1and R2are 0-Ω resistors that keep the output in the fixed output voltage mode when
populated. R1connects the Feedback pin to the V
pin.
Figure 5. R1and R2Used to Set Fixed Voltage Mode on EVM
8
pin, while R2connects the Sense pin and the Output
TAP
4
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2.6 Adjustable Output Voltage Resistors
Resistors R3-R6can be populated to set a desired output voltage. To do so, resistors R1and R2must first
be removed. Resistors R4-R6form a voltage divider and can be populated with values based on the
desired output voltage by following the equation on the EVM. R3must be populated with a 0-Ω resistor to
short the Feedback pin of the device to the voltage divider of R4-R6. See Section 3.2.2 for additional
information regarding setting an adjustable output voltage.
Figure 6. Resistors R3-R6Used to Set Output Voltage in Adjustable Voltage Mode
HW Description
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LP2951EVM
5
Setup
3 Setup
These sections describe the jumpers and connectors on the EVM as well as how to properly connect,
setup, and use the LP2951EVM.
3.1 Input/Output Connectors and Jumper Description
NOTE: Connectors J1-J3 and J12-J14 are blank SMB connectors. These can be populated, or wires
can be soldered directly to them. The middle connection of the connector is the signal, while
the four edge connections are all ground.
3.1.1 J5 - Input
Input for power. Connect supply to this connector.
3.1.2 J6- Feedback
Determines the output voltage. Connected to V
3.1.3 J7 - ERROR
Error output connector. This active low output determines if the output voltage is within 6% of its expected
value.
through R1with standard setup.
TAP
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3.1.4 J4/J8 - GND
Return path connectors.
3.1.5 J9 - Output
Regulated output voltage connectors.
3.1.6 J10 - Sense
Output voltage sensing connectors.
3.1.7 J11 - Shutdown
Device shutdown connectors. By shorting the middle pin of J11 to the pin labeled as N, the device
remains active. If the middle pin of J11 is shorted to the pin labeled Y, the device will shutdown. See
Table 2 for shutdown jumper position connection.
Table 2. Shutdown Jumper Position Versus Output
Jumper Position Output
N Enabled
Y Disabled
6
LP2951EVM
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