P21XXCSR-EVB 데이터 시트보기 (PDF) - Unspecified

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P21XXCSR-EVB

Powerharvester® Chipset Reference Design Evaluation Board

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P21XXCSR-EVB

P21XX Powerharvester® Chipset Reference Design

Evaluation Board

Selecting/Setting Output Voltage

S1 is used to select between three output voltage options for VOUT. Selecting DEFAULT sets VOUT to

3.3V. Selecting 4.1V or 4.2V changes VOUT to the labeled voltage. The DEFAULT setting can also be

adjusted to any voltage between 2.0V and 5.5V simply by changing the resistors R1 and R2 and using

the DEFAULT switch postion. The equation for determining R1 and R2 is as follows:

It is recommended that a 1MΩ be used for R1, which is connected between VOUT and VSET. With this in

mind, some common values for VOUT would result in the following R2 values:

For VOUT = 3.3V, R2 = 578.9kΩ (576kΩ std)

For VOUT = 4.1V, R2 = 418.7kΩ (417kΩ std)

For VOUT = 4.2V, R2 = 404.7kΩ (407kΩ std)

It should be noted that changing R1 or R2 will change the voltage set by switch S1. Care should be

taken to ensure the absolute maximum voltage is not exceeded.

Selecting DSET

S2 is used to select how DSET and DOUT function on the board. Selecting OFF will allow the P21XXCSR-

EVB to operate normally. If it is desired to monitor DOUT, selecting VOUT will tie DSET to VOUT through a

resistor, R6. In this mode, when VOUT is on, DSET will be pulled high and DOUT can be used to measure

RSSI or to retrieve data from the RF field. Selecting DSET EXT will allow DSET to be controlled externally

using the DSET EXT test point.

LED, Prototyping, and Measuring Current

S3 is used to control flow of current from VOUT. Selecting LED will tie VOUT to the on-board LED, D3, to

be a visual indicator that the system working. Selecting VCC will tie VOUT to the prototype area and

output switch. NOTE: VOUT is routed to the header P1 in parallel with S3, so VOUT is present on the

header pins regardless of S3 position. If using the P1 header, S3 should be in the MEAS position, as the

other positions could use more power, resulting in longer charging periods on the storage cap.

Selecting MEAS allows for current to be measure by connected a current probe between test points

VOUT and LED or VOUT and VCC. Current should be measured using an oscilloscope, as the time period of

VOUT being on is generally too short to be seen on a multi-meter.

Output Switch and Batteries

With S3 in the VCC position, the output switch is activated. The output switch includes C4, Q5, Q6, R17

and R18, and is necessary when using the P21XXCSR-EVB to charge a battery. The switch limits the

current draw on the battery from the P21XXCSR-EVB to 10-20nA. This ensures the P21XXCSR-EVB does

not discharge the battery during periods of non-harvesting.

P21XXCSR-EVB v1.0 – 2014/7

© 2014 Powercast Corporation, All rights reserved.

www.powercastco.com / contact@powercastco.com

+1 412-455-5800

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