MCP4728 datasheet(21/66 Pages) MICROCHIP

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DS22187C-page 21

MCP4728

3.0

PIN DESCRIPTIONS

The descriptions of the pins are listed in Table 3-1.

3.1

Analog Output Voltage Pins (V

OUTA,

OUTB, V

OUTC, VOUTD)

The device has four analog voltage output (VOUT) pins.

Each output is driven by its own output buffer with a

gain of 1 or 2 depending on the gain and VREF selection

bit settings. In normal mode, the DC impedance of the

output pin is about 1

Ω. In Power-Down mode, the

output pin is internally connected to 1 k

Ω, 100 kΩ, or

500 k

Ω, depending on the Power-Down selection bit

settings.

The VOUT pin can drive up to 1000 pF of capacitive

load. It is recommended to use a load with RL greater

than 5 k

Ω.

3.2

Supply Voltage Pins (V

DD, VSS)

VDD is the power supply pin for the device. The voltage

at the VDD pin is used as the power supply input as well

as the DAC external reference. The power supply at

the VDD pin should be as clean as possible for a good

DAC performance.

It is recommended to use an appropriate bypass

capacitor of about 0.1 µF (ceramic) to ground. An

additional 10 µF capacitor (tantalum) in parallel is also

recommended to further attenuate high frequency

noise present in application boards. The supply voltage

(VDD) must be maintained in the 2.7V to 5.5V range for

specified operation.

VSS is the ground pin and the current return path of the

device. The user must connect the VSS pin to a ground

plane through a low impedance connection. If an

analog ground path is available in the application PCB

(printed circuit board), it is highly recommended that

the VSS pin be tied to the analog ground path or

isolated within an analog ground plane of the circuit

board.

TABLE 3-1:

PIN FUNCTION TABLE

Pin No.

Name

Pin Type

Function

VDD

Supply Voltage

2SCL

I2C Serial Clock Input.

(Note 1)

SDA

OI/OO

I2C Serial Data Input and Output.

(Note 1)

4LDAC

This pin is used for two purposes:

(a) Synchronization Input. It is used to transfer the contents of the DAC input

registers to the output registers (VOUT).

(b) Select the device for reading and writing I2C address bits.

(Note 2)

RDY/BSY

This pin is a status indicator of EEPROM programming activity. An external pull-up

resistor (about 100 k

Ω) is needed from RDY/BSY pin to V

DD line. (Note 1)

6VOUT A

Buffered analog voltage output of channel A. The output amplifier has rail-to-rail

operation.

7VOUT B

Buffered analog voltage output of channel B. The output amplifier has rail-to-rail

operation.

8VOUT C

Buffered analog voltage output of channel C. The output amplifier has rail-to-rail

operation.

9VOUT D

Buffered analog voltage output of channel D. The output amplifier has rail-to-rail

operation.

VSS

Ground reference.

Legend: P = Power, OI = Open-Drain Input, OO = Open-Drain Output, ST = Schmitt Trigger Input Buffer,

AO = Analog Output

Note 1: This pin needs an external pull-up resistor from V

DD line. Leave this pin float if it is not used.

2: This pin can be driven by MCU.

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