LP2951-N_15_15 Datasheet, PDF (31/50 Pages) Texas Instruments – LP295x-N Series of Adjustable Micropower Voltage Regulators

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LP2950-N, LP2951-N
SNVS764O – JANUARY 2000 – REVISED DECEMBER 2014
10 Power Supply Recommendations
The LP2950-N and LP2951-N are designed to operate from an input voltage supply range between 2.3 V and 30
V. The input voltage range provides adequate headroom in order for the device to have a regulated output. This
input supply must be well regulated. If the input supply is noisy, additional input capacitors with low ESR can help
improve the output noise performance.
11 Layout
11.1 Layout Guidelines
For best overall performance, place all circuit components on the same side of the circuit board and as near as
practical to the respective LDO pin connections. Place ground return connections to the input and output
capacitor, and to the LDO ground pin as close to each other as possible, connected by a wide, component-side,
copper surface. The use of vias and long traces to create LDO circuit connections is strongly discouraged and
negatively affects system performance. This grounding and layout scheme minimizes inductive parasitics, and
thereby reduces load-current transients, minimizes noise, and increases circuit stability.
A ground reference plane is also recommended and is either embedded in the PCB itself or located on the
bottom side of the PCB opposite the components. This reference plane serves to assure accuracy of the output
voltage, shield noise, and behaves similar to a thermal plane to spread (or sink) heat from the LDO device. In
most applications, this ground plane is necessary to meet thermal requirements.
11.2 Layout Example
Ground
1
2
3
VOUT
Output
Capacitor
OUT
SENSE
SHUTDOWN
GND
Ground
Input
Capacitor
IN
VIN
FEEDBACK
VTAP
ERROR
Error Pullup
Resistor
VOUT
Input
Output
Capacitor Capacitor
VIN
VOUT
Figure 56. LP2950 Board Layout
Figure 57. LP2951 Board Layout
11.3 WSON Mounting
The NGT (No Pullback) 8-Lead WSON package requires specific mounting techniques which are detailed in TI
Application Note 1187, Leadless Leadframe Package (LLP) (SNOA401). Referring to the PCB Design
Recommendations section, it should be noted that the pad style which should be used with the WSON package
is the NSMD (non-solder mask defined) type. Additionally, it is recommended the PCB terminal pads to be 0.2
mm longer than the package pads to create a solder fillet to improve reliability and inspection.
The thermal dissipation of the WSON package is directly related to the printed circuit board construction and the
amount of additional copper area connected to the DAP.
For the LP2951-N in the NGT 8-Lead WSON package, the junction-to-case thermal rating, R_θJC, is 35°C/W,
where the case is the bottom of the package at the center of the DAP.
Copyright © 2000–2014, Texas Instruments Incorporated
Product Folder Links: LP2950-N LP2951-N
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