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Design Revision History

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SPRUIM4B–December 2018–Revised May 2020

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xWR1843 Evaluation Module (xWR1843BOOST) Single-Chip mmWave

Sensing Solution

3.2.2 Power Supply Optimization

For best transient supply settling at the start of the chirp, the [idle time + TX start time] can be set to a

value < 10 µsec. In this configuration, the AWR firmware keeps some of the RF blocks ON between the

chirps. For idle time + Tx start time > 10 µsec, the blocks are turned off for power saving. In this case, TI

recommends adding an additional resistive load on the 1-V LDO oputput; the available R83 pad can be

used for this purpose. The value of the resistance can be between 10 to 30 Ω, depending on the idle time

setting. The other option is to disable the inter-chirp power save feature of the AWR device using the

AWR DYNAMICPOWERSAVE CONF SET SB API.

The LC filter on the 1-V and 1.8-V supplies is used to filter the 4-Mhz ripple from the switcher. There could

be small ringing behavior at the point of transient load change. If this is impacting the RX sampled data,

the ADC start time can be increased to a point where the supply is settled within 5%, or the inductance

value can be reduced to reduce the ringing (which may come at the expense or poorer 4-Mhz filtering).

4 Design Revision History

Table 6. Design Revision History

PCB Revision Change Description

Rev C Increased LDO output cap to 47 µF

Added two optional 100-µF LDO output caps

Added 10-µF cap to LDO output

Added test pad to LDO PG pin

Connected LDO DNC pads to GND for thermal performance

Added optional bleeed resistor on LDO output

Changed 1-V filtering to BLM18 inductor

Added 22-µF caps to 1-V, 1.24-C, and 1.8-V LC filters

Added 10-µF cpas to 3.3-V and 1.24-V LC filters

Added additional 10-µF caps to 1-V LC fitlers

5 Mechanical Mounting of PCB

The field of view of the radar sensor is orthogonal to the PCB. To enable easy measurements on the

sensing objects on the horizontal plane, the PCB can be mounted vertically. The L-brackets provided with

the xWR1843 EVM kit, along with the screws and nuts help in the vertical mounting of the EVM. Figure 23

shows how the L-brackets can be assembled.

Texas Instruments WR1843 Series User Manual

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