Datasheet

 2010 Microchip Technology Inc. DS22249A-page 15
MCP4802/4812/4822
3.0 PIN DESCRIPTIONS
The descriptions of the pins are listed in Tab l e 3-1.
3.1 Supply Voltage Pins (V
DD,
V
SS
)
V
DD
is the positive supply voltage input pin. The input
supply voltage is relative to V
SS
and can range from
2.7V to 5.5V. The power supply at the V
DD
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.
V
SS
is the analog ground pin and the current return path
of the device. The user must connect the V
SS
pin to a
ground plane through a low-impedance connection. If
an analog ground path is available in the application
Printed Circuit Board (PCB), it is highly recommended
that the V
SS
pin be tied to the analog ground path or
isolated within an analog ground plane of the circuit
board.
3.2 Chip Select (CS)
CS is the Chip Select input pin, which requires an
active-low to enable serial clock and data functions.
3.3 Serial Clock Input (SCK)
SCK is the SPI compatible serial clock input pin.
3.4 Serial Data Input (SDI)
SDI is the SPI compatible serial data input pin.
3.5 Latch DAC Input (LDAC)
LDAC (latch DAC synchronization input) pin is used to
transfer the input latch registers to their corresponding
DAC registers (output latches, V
OUT
). When this pin is
low, both V
OUTA
and V
OUTB
are updated at the same
time with their input register contents. This pin can be
tied to low (V
SS
) if the V
OUT
update is desired at the
rising edge of the CS
pin. This pin can be driven by an
external control device such as an MCU I/O pin.
3.6 Analog Outputs (V
OUTA
, V
OUTB
)
V
OUTA
is the DAC A output pin, and V
OUTB
is the DAC
B output pin. Each output has its own output amplifier.
The full-scale range of the DAC output is from
V
SS
to G* V
REF
, where G is the gain selection option
(1x or 2x). The DAC analog output cannot go higher
than the supply voltage (V
DD
).
TABLE 3-1: PIN FUNCTION TABLE FOR MCP4802/4812/4822
MCP4802/4812/4822
Symbol Description
MSOP, PDIP, SOIC
1V
DD
Supply Voltage Input (2.7V to 5.5V)
2CSChip Select Input
3 SCK Serial Clock Input
4 SDI Serial Data Input
5LDAC
Synchronization Input. This pin is used to transfer DAC settings
(Input Registers) to the output registers (V
OUT
)
6V
OUTB
DAC
B
Output
7V
SS
Ground reference point for all circuitry on the device
8V
OUTA
DAC
A
Output