MCP3002-I/P Microchip Technology, MCP3002-I/P Datasheet - Page 15

• Manufacturer Part Number: MCP3002-I/P
• Description: IC ADC 10BIT 2.7V 2CH SPI 8-DIP
• Manufacturer: Microchip Technology

Specifications of MCP3002-I/P

• Package / Case: 8-DIP (0.300", 7.62mm)
• Number Of Bits: 10
• Sampling Rate (per Second): 200k
• Data Interface: Serial, SPI™
• Number Of Converters: 1
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Through Hole
• Architecture: SAR
• Conversion Rate: 200 KSPs
• Input Type: Voltage
• Maximum Operating Temperature: + 85 C
• Mounting Style: Through Hole
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

4.0
The MCP3002 A/D converter employs a conventional
SAR architecture. With this architecture, a sample is
acquired on an internal sample/hold capacitor for
1.5 clock cycles starting on the second rising edge of
the serial clock after the start bit has been received.
Following this sample time, the input switch of the
converter opens and the device uses the collected
charge on the internal sample and hold capacitor to
produce a serial 10-bit digital output code. Conversion
rates of 200 ksps are possible on the MCP3002. See
Section 6.2 “Maintaining Minimum Clock Speed” for
information on minimum clock rates. Communication with
the device is done using a 3-wire SPI compatible interface.
4.1
The MCP3002 device offers the choice of using the
analog input channels configured as two single-ended
inputs that are referenced to V
differential input. The configuration setup is done as part
of the serial command before each conversion begins.
When used in the psuedo-differential mode, CH0 and
CH1 are programmed as the IN+ and IN- inputs as part
of the command string transmitted to the device. The
IN+ input can range from IN- to the reference voltage,
V
rail. The IN- input can be used to cancel small signal
common-mode noise which is present on both the IN+
and IN- inputs.
For the A/D converter to meet specification, the charge
holding capacitor (C
time to acquire a 10-bit accurate voltage level during
the 1.5 clock cycle sampling period. The analog input
model is shown in
In this diagram, it is shown that the source impedance
(R
impedance, directly affecting the time that is required to
charge the capacitor, C
source impedances increase the offset, gain, and
integral linearity errors of the conversion.
Ideally, the impedance of the signal source should be
near zero. This is achievable with an operational
amplifier such as the MCP601 which has a closed loop
output impedance of tens of ohms. The adverse affects
of higher source impedances are shown in
When operating in the pseudo-differential mode, if the
voltage level of IN+ is equal to or less than IN-, the
resultant code will be 000h. If the voltage at IN+ is equal
to or greater than {[V
put code will be 3FFh. If the voltage level at IN- is more
than 1 LSB below V
input will have to go below V
code. Conversely, if IN- is more than 1 LSB aboveV
then the 3FFh code will not be seen unless the IN+
input level goes above V
is equal to or greater than {[V
the output code will be 3FFh.
© 2008 Microchip Technology Inc.
DD
S
) adds to the internal sampling switch (R
. The IN- input is limited to ±100 mV from the V
DEVICE OPERATION
Analog Inputs
Figure
SS
DD
SAMPLE
, then the voltage level at the IN+
+ (IN-)] - 1 LSB}, then the out-
DD
SAMPLE
4-1.
level. If the voltage at IN+
) must be given enough
SS
DD
. Consequently, larger
SS
to see the 000h output
+ (IN-)] - 1 LSB}, then
or a single pseudo-
Figure
4-2.
SS
SS
SS
)
,
4.2
The digital output code produced by an A/D Converter
is a function of the input signal and the reference
voltage. For the MCP3002, V
reference voltage.
As the V
accordingly. The theoretical digital output code
produced by the A/D Converter is shown below.
Where:
V
V
DD
IN
DD
Digital Output Code
Digital Output Code
level is reduced, the LSB size is reduced
=
=
analog input voltage
supply voltage
LSB Size
=
MCP3002
V
------------- -
1024
=
REF
DD
1024*V
------------------------ -
DS21294D-page 15
V
is used as the
DD
IN