LDC1101_15 Datasheet, PDF (44/54 Pages) Texas Instruments – LDC1101 1.8 V High-Resolution, High-Speed Inductance-to-Digital Converter

LDC1101
SNOSD01B – MAY 2015 – REVISED JULY 2015
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10 Power Supply Recommendations
A parallel set of 1 µF and 0.1 µF capacitors should be used to bypass V_DD, although it may be necessary to
include a larger capacitor with systems which have a larger amount of supply variation. The smallest value
capacitor should be placed as close as possible to the VDD pin. A ground plane is recommended to connect
both the ground and the Die Attach Pad (DAP).
C_LDO capacitor should be nonpolarized and have an equivalent series resistance (ESR) less than 1 Ω, with a
SRF of at least 24 MHz.
11 Layout
11.1 Layout Guidelines
The LDC1101 requires minimal external components for effective operation. Following good layout techniques -
providing good grounding and clean supplies are critical for optimum operation. Due to the small physical size of
the LDC1101, use of surface mount 0402 or smaller components can ease routing.
11.1.1 Ground and Power Planes
Ground and power planes are helpful for maintaining a clean supply to the LDC1101. In the layout shown in
Figure 61, a top-layer ground fill is also used for improved grounding.
11.1.2 CLKIN Routing
The CLKIN pin routing should maintain consistent impedance; typically this is 50Ω, but can be adjusted based on
board geometries. If a parallel termination resistor is used, it should be placed as close as possible to the CLKIN
pin. Minimize layer changes and routing through vias for the CLKIN signal. Maintain an uninterrupted ground
plane under the trace.
11.1.3 Capacitor Placement
The capacitor C_LDO should be placed as close as possible to the CLDO pin.
Place the bypass capacitors as close as possible to the VDD pin, with the smaller valued capacitor placed closer.
11.1.4 Sensor Connections
The sensor capacitor should be as close as possible to the sensor inductor. The INA and INB traces should be
routed in parallel and as close as possible to each other to minimize coupling of noise. If cable is to be used,
then INA and INB should be a twisted pair or in coaxial cable. The distance between the INA/INB pins and the
sensor will affect the maximum possible sensor frequency. For some applications, it may be helpful to place
small value capacitor (for example, 10 pF) from INA to ground and INB to ground; these capacitors should be
located close to the INA and INB pins.
Refer to Application Note LDC Sensor Design (SNOA930) for additional information on sensor design.
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