MCP3004-I/SL Microchip Technology, MCP3004-I/SL Datasheet - Page 17

• Manufacturer Part Number: MCP3004-I/SL
• Description: IC ADC 10BIT 2.7V 4CH SPI 14SOIC
• Manufacturer: Microchip Technology

Specifications of MCP3004-I/SL

• Data Interface: Serial, SPI™
• Number Of Bits: 10
• Sampling Rate (per Second): 200k
• Number Of Converters: 1
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 14-SOIC (0.154", 3.90mm Width)
• Resolution (bits): 10bit
• Sampling Rate: 200kSPS
• Input Channel Type: Pseudo Differential, Single Ended
• Supply Voltage Range - Analog: 2.7V To 5.5V
• Supply Current: 425µA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

4.0
The MCP3004/3008 A/D converters
conventional SAR architecture. With this architecture,
a sample is acquired on an internal sample/hold
capacitor for 1.5 clock cycles starting on the first rising
edge of the serial clock once CS has been pulled low.
Following this sample time, 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 100 ksps are possible on the
MCP3004/3008. See Section 6.2 “Maintaining Mini-
mum Clock Speed”, “Maintaining Minimum Clock
Speed”, for information on minimum clock rates.
Communication with the device is accomplished using
a 4-wire SPI-compatible interface.
4.1
The MCP3004/3008 devices offer the choice of using
the analog input channels configured as single-ended
inputs or pseudo-differential pairs. The MCP3004 can
be configured to provide two pseudo-differential input
pairs or four single-ended inputs. The MCP3008 can be
configured to provide four pseudo-differential input
pairs or eight single-ended inputs. Configuration is
done as part of the serial command before each
conversion begins. When used in the pseudo-
differential mode, each channel pair (i.e., CH0 and
CH1, CH2 and CH3 etc.) are programmed as the IN+
and IN- inputs as part of the command string transmit-
ted to the device. The IN+ input can range from IN- to
(V
the V
signal common-mode noise, which is present on both
the IN+ and IN- inputs.
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
the output code will be 3FFh. If the voltage level at IN-
is more than 1 LSB below V
IN+ input will have to go below V
output code. Conversely, if IN- is more than 1 LSB
above V
IN+ input level goes above V
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
This diagram illustrates that the source impedance (R
adds to the internal sampling switch (R
directly affecting the time that is required to charge the
capacitor (C
impedances increase the offset, gain and integral
linearity errors of the conversion (see
© 2008 Microchip Technology Inc.
REF
SS
+ IN-). The IN- input is limited to ±100 mV from
rail. The IN- input can be used to cancel small
SS
DEVICE OPERATION
Analog Inputs
, the 3FFh code will not be seen unless the
SAMPLE
Figure
). Consequently, larger source
SAMPLE
4-1.
REF
SS
) must be given enough
REF
, the voltage level at the
+ (IN-)] - 1 LSB}, then
level.
SS
Figure
to see the 000h
SS
) impedance,
employ a
4-2).
S
)
4.2
For each device in the family, the reference input
(V
the reference input is reduced, the LSB size is reduced
accordingly.
EQUATION 4-1:
The theoretical digital output code produced by the A/D
converter is a function of the analog input signal and
the reference input, as shown below.
EQUATION 4-2:
When using an external voltage reference device, the
system
manufacturer’s recommendations for circuit layout.
Any instability in the operation of the reference device
will have a direct effect on the operation of the A/D
converter.
REF
Where:
) determines the analog input voltage range. As
V
REF
Reference Input
V
designer
Digital Output Code
IN
MCP3004/3008
=
=
LSB Size
should
analog input voltage
analog input voltage
LSB SIZE CALCULATION
DIGITAL OUTPUT CODE
CALCULATION
=
=
always
V
------------ -
1024
REF
1024 V
-------------------------- -
V
REF
DS21295D-page 17
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refer
IN
to
the