Datasheet

 2010 Microchip Technology Inc. DS22248A-page 17
MCP4901/4911/4921
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. It
is recommended to use an appropriate bypass capaci-
tor of about 0.1 µF (ceramic) to ground. 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, which requires an active-low
signal to enable serial clock and data functions.
3.3 Serial Clock Input (SCK)
SCK is the SPI compatible serial clock input.
3.4 Serial Data Input (SDI)
SDI is the SPI compatible serial data input.
3.5 Latch DAC Input (LDAC)
The LDAC (latch DAC synchronization input) pin is
used to transfer the input latch register to the DAC reg-
ister (output 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
external 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 Voltage Reference Input (V
REF
)
V
REF
is the voltage reference input for the device. The
reference on this pin is utilized to set the reference
voltage on the string DAC. The input voltage can range
from V
SS
to V
DD
. This pin can be tied to VDD.
3.8 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
PDIP, MSOP, SOIC DFN Symbol Description
11V
DD
Supply Voltage Input (2.7V to 5.5V)
22CSChip Select Input
3 3 SCK Serial Clock Input
4 4 SDI Serial Data Input
55LDAC
DAC Output Synchronization Input. This pin is used to transfer
the input register (DAC settings) to the output register (V
OUT
)
66V
REF
Voltage Reference 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