LP2989_15 Datasheet, PDF (20/34 Pages) Texas Instruments – LP2989 Micropower and Low-Noise, 500-mA Ultra Low-Dropout Regulator for Use With Ceramic Output Capacitors

LP2989
SNVS083O – FEBRUARY 2005 – REVISED MARCH 2015
www.ti.com
9 Power Supply Recommendations
The LP2989 is designed to operate from an input voltage supply range from 2.1 V to 16 V. The input voltage
range provides adequate headroom 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.
10 Layout
10.1 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.
10.2 Layout Example
Input
Capacitor
VIN
BYPASS
N/C
GROUND
IN
Ground
SHUTDOWN
ERROR
Error Pullup
Resistor
VOUT
SENSE
OUT
VOUT
Output
Capacitor
Figure 44. Layout Example
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