MCP23009T-ESS 查看數據表（PDF） - Microchip Technology

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MCP23009T-ESS

8-Bit I/O Expander with Open-Drain Outputs

Microchip Technology 

MCP23009/MCP23S09

1.4 Multi-Bit Address Decoder

The ADDR pin is used to set the slave address of the

MCP23009 (I2C only) to allow up to eight devices on

the bus using only a single pin. Typically, this would

require three pins.

The multi-bit Address Decoder employs a basic FLASH

ADC architecture (Figure 1-4). The seven comparators

generate eight unique values based on the analog

input. This value is converted to a 3-bit code which

corresponds to the address bits (A2, A1, A0) in the

serial OPCODE.

Sequence of operation (see Figure 1-5 for

timings):

1. Upon power-up (after VDD stabilizes), the

module becomes active after time tADEN. Note

that the analog value on the ADDR pin must be

stable before this point to ensure accurate

address assignment.

2. The 3-bit address is latched after tADDRLAT.

3. The module powers down after the first rising

edge of the serial clock is detected (tADDIS).

Once the address bits are latched, the device will keep

the slave address until a POR or Reset condition

occurs.

FIGURE 1-2:

VOLTAGE DIVIDER EXAMPLE

1.4.1 CALCULATING VOLTAGE ON ADDR

When calculating the required voltage on the ADDR pin

(V2), the set point should be the mid point of the LSb of

the ADC.

The examples in Figures 1-2 and 1-3 show how to

determine the mid-point voltage (V2) and the range of

voltages based on a voltage divider circuit. The

maximum tolerance is 20%, however, it is

recommended to use 5% tolerance worst-case (10%

total tolerance).

VDD

ADDR

VDD

R1

V2

MCP23009 Only

A0

A1

A2

R2

VSS

VSS

 2009-2014 Microchip Technology Inc.

DS20002121C-page 9

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