MCP48CMB21 datasheet(41/106 Pages) MICROCHIP

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 2019 Microchip Technology Inc.

DS20006160A-page 41

MCP48CXBXX

3.1

Positive Power Supply Input (VDD)

VDD is the positive supply voltage input pin. The input

supply voltage is relative to VSS.

The power supply at the VDD pin should be as clean as

possible

for

good

DAC

performance.

recommended to use an appropriate bypass capacitor

of about 0.1 µF (ceramic) to ground as close as

possible to the pin. An additional 10 µF capacitor

(tantalum) in parallel is also recommended to further

attenuate noise present in application boards.

3.2

Ground (VSS)

The VSS pin is the device ground reference.

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.

3.3

Voltage Reference Pin (VREF)

The VREF pin is either an input or an output. When the

DAC’s voltage reference is configured as the VREF pin,

the pin is an input. When the DAC’s voltage reference is

configured as the internal band gap, the pin is an output.

When the DAC’s voltage reference is configured as the

VREF pin, there are two options for this voltage input:

VREF pin voltage is buffered or unbuffered. The

buffered option is offered in cases where the external

reference voltage does not have sufficient current

capability to not drop its voltage when connected to the

internal resistor ladder circuit.

When the DAC’s voltage reference is configured as the

device VDD, the VREF pin is disconnected from the

internal circuit.

When the DAC’s voltage reference is configured as the

internal band gap, the VREF pin’s drive capability is

minimal, so the output signal should be buffered.

See Section 5.2 “Voltage Reference Selection” and

3.4

No Connect (NC)

The NC pin is not internally connected to the device.

3.5

Analog Output Voltage Pins

(VOUT0, VOUT1)

VOUT0 and VOUT1 are the DAC analog voltage output

pins. Each DAC output has an output amplifier. The DAC

output range depends on the selection of the voltage

reference source (and potential Output Gain selection).

These are:

• Device VDD - The full-scale range of the DAC

output is from VSS to approximately VDD.

•VREF pin - The full-scale range of the DAC output

is from VSS to G x VRL, where G is the gain

selection option (1X or 2X).

• Internal Band Gap - The full-scale range of the

DAC output is from VSS to G X VBG, where G is

the gain selection option (1X or 2X).

In Normal mode, the DC impedance of the output pin is

about 1

. In Power-Down mode, the output pin is

internally connected to a known pull-down resistor of

, 100 k, or open. The Power-Down selection bits

settings are shown in Register 4-3 (Table 5-5).

3.6

Latch/High-Voltage Command Pin

(LAT/HVC)

The DAC output value update event can be controlled

and synchronized using the LAT pin, for one or both

channels, on a single or different devices.

The LAT pin controls the effect of the volatile wiper

registers, VRxB:VRxA, PDxB:PDxA and Gx bits on the

DAC output.

If the LAT pin is held at VIH, the values sent to the

volatile wiper registers and configuration bits have no

effect on the DAC outputs.

Once voltage on the pin transitions to VIL, the values in

the volatile wiper registers and configuration bits are

transferred to the DAC outputs.

The pin is level-sensitive, so writing to the volatile wiper

registers and configuration bits, while it is being held at

VIL, will trigger an immediate change in the outputs.

For dual output devices in MSOP and DFN packages,

the LAT pin controls both channels at the same time.

The HVC pin allows the device’s MTP memory to be

programmed for the MCP48CMBXX devices. The

programming voltage supply should provide 7.5V and

at least 6.4 mA.

Note:

The HVC pin should have voltages

greater than 5.5V present only during the

MTP

programming

operation.

Using

voltages greater than 5.5V for an

extended time on the pin may cause

device reliability issues.

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