ATSHA204A datasheet(27/93 Pages) MICROCHIP

27 / 93 page

Figure 5-1. 3-wire Configuration for Single-Wire Interface

VCC

SDA

GND

5.6.1

2-lead Configuration

There is an internal gated switch that is connected between the SDA and VCC pins which permits the

ATSHA204A to steal power from the SDA pin and store it on the bypass capacitor. In this case, the VCC

pin does not need to be connected to the Host’s power supply. This configuration permits the board

containing the ATSHA204A and a bypass capacitor to be connected to the Host’s microprocessor using

just two leads (that is, SDA and GND).

If the system supply voltage level is at least 3V, the pull-up resistor should be no greater than 1K and the

capacitor no less than 0.03 μF. The device operates properly keeping VCC at or above the specification

level of 2V. Contact Microchip for other configuration information.

In a 2-lead configuration, the SDA pin must be driven high to VCC using an active driver capable of

supplying ICC for the entire duration of any command execution and a totem pole driver should be used to

send data to the device. The SDA line should only be reliant on the pull-up resistor during transmission of

data from the ATSHA204A to the system

Figure 5-2. 2-lead Configuration for Single-Wire Interface

VCC

SDA

GND

ATSHA204A

Single-Wire Interface

DS40002025A-page 27

ATSHA204A Datasheet(PDF) 27 Page - Microchip Technology