Datasheet

 2010 Microchip Technology Inc. DS22244B-page 15
MCP4801/4811/4821
3.0 PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 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 good DAC performance.
Using an appropriate bypass capacitor of about 0.1 µF
(ceramic) to ground is recommended. An additional
10 µF capacitor (tantalum) in parallel is also recom-
mended 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 register to the DAC register (out-
put latches, V
OUT
). When this pin is low, V
OUT
is
updated with input register content. 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 exter-
nal control device such as an MCU I/O pin.
3.6 Analog Output (V
OUT
)
V
OUT
is the DAC analog output pin. The DAC output
has an 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
).
3.7 Exposed Thermal Pad (EP)
There is an internal electrical connection between the
exposed thermal pad (EP) and the V
SS
pin. They must
be connected to the same potential on the PCB.
TABLE 3-1: PIN FUNCTION TABLE FOR MCP4801/4811/4821
MCP4801/4811/4821
Symbol Description
MSOP, PDIP,
SOIC, DFN
DFN
11V
DD
Supply Voltage Input (2.7V to 5.5V)
22CS
Chip Select Input
3 3 SCK Serial Clock Input
4 4 SDI Serial Data Input
55
LDAC
DAC Output Synchronization Input. This pin is used to transfer the input
register (DAC settings) to the output register (V
OUT
)
66
SHDN
Hardware Shutdown Input
77V
SS
Ground reference point for all circuitry on the device
88V
OUT
DAC Analog Output
— 9 EP Exposed thermal pad. This pad must be connected to V
SS
in application