MCP4812-E/MS Microchip Technology, MCP4812-E/MS Datasheet - Page 31

• Manufacturer Part Number: MCP4812-E/MS
• Description: DAC 10BIT DUAL SPI/VREF 8MSOP
• Manufacturer: Microchip Technology

Specifications of MCP4812-E/MS

• Number Of Converters: 2
• Settling Time: 4.5µs
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Number Of Bits: 10
• Data Interface: Serial, SPI™
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Number Of Dac Outputs: 2
• Resolution: 10 bit
• Interface Type: SPI
• Supply Voltage (max): 6.5 V
• Supply Voltage (min): 2.7 V
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 55 C
• Supply Current: 415 uA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power Dissipation (max): -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

6.9
Example 6-6
programmable current source using a voltage follower.
The current sensor (sensor resistor) is used to convert
the DAC voltage output into a digitally-selectable
current source.
Adding the resistor network from
be advantageous in this application. The smaller
R
EXAMPLE 6-6:
 2010 Microchip Technology Inc.
SENSE
I
where
I
L
b
=
=
-------------- -
R
V
Building Programmable Current
Source
is, the less power dissipated across it.
I
----

(a) Single Output DAC:
(b) Dual Output DAC:

L
sense
OUT
Common-Emitter Current Gain
shows an example of building a

------------ -

+

1
DIGITALLY-CONTROLLED CURRENT SOURCE
MCP4801
MCP4811
MCP4821
MCP4802
MCP4812
MCP4822
Example 6-2
SPI
would
3-wire
V
DAC
DD
D
G
N
n
=
=
=
=
=
Gain selection (1x or 2x)
Digital value of DAC (0-255) for MCP4801/MCP4802
Digital value of DAC (0-1023) for MCP4811/MCP4812
Digital value of DAC (0-4095) for MCP4821/MCP4822
DAC bit resolution
However, this also reduces the resolution that the
current can be controlled with. The voltage divider, or
“window”, DAC configuration would allow the range to
be reduced, thus increasing resolution around the
range of interest. When working with very small sensor
voltages, plan on eliminating the amplifier’s offset error
by storing the DAC’s setting under known sensor
conditions.
V
OUT
MCP4802/4812/4822
V
V
CC
CC
–
+
R
I
SENSE
b
V
DD
Load
or V
REF
I
L
DS22249A-page 31