MCP3903-I/SS Microchip Technology, MCP3903-I/SS Datasheet - Page 27

• Manufacturer Part Number: MCP3903-I/SS
• Description: IC AFE 24BIT 64KSPS 28SSOP
• Manufacturer: Microchip Technology
• Series: -r

Specifications of MCP3903-I/SS

• Featured Product: MCP3903 Six Channel ΔΣ A/D Converter
• Number Of Bits: 24
• Number Of Channels: 6
• Power (watts): -
• Voltage - Supply, Analog: 4.5 V ~ 5.5 V
• Voltage - Supply, Digital: 2.7 V ~ 3.6 V
• Package / Case: 28-SSOP (0.209", 5.30mm Width)
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

TABLE 5-5:
TABLE 5-6:
5.6
5.6.1
The MCP3903 contains an internal voltage reference
source specially designed to minimize drift over
temperature. In order to enable the internal voltage
reference, the VREFEXT bit in the configuration
register must be set to 0 (default mode). This internal
V
typical value of this voltage reference is 2.35V ±2%.
The internal reference has a very low typical
temperature coefficient of ±5 ppm/°C, allowing the out-
put codes to have minimal variation with respect to
temperature since they are proportional to (1/V
The noise of the internal voltage reference is low
enough not to significantly degrade the SNR of the
ADC if compared to a precision external low-noise
voltage reference.
The output pin for the internal voltage reference is
REFIN+/OUT.
When the internal voltage reference is enabled,
REFIN- pin should always be connected to AGND.
For optimal ADC accuracy, appropriate bypass
capacitors should be placed between REFIN+/OUT
and AGND. De-coupling at the sampling frequency,
around 1 MHz, is important for any noise around this
frequency will be aliased back into the conversion data.
0.1 µF ceramic and 10 µF tantalum capacitors are
recommended.
© 2011 Microchip Technology Inc.
0 1 1 1
0 1 1 1
0 0 0 0
1 1 1 1
1 0 0 0
1 0 0 0
0 1 1 1
0 1 1 1
0 0 0 0
1 1 1 1
1 0 0 0
1 0 0 0
REF
supplies reference voltage to both channels. The
Voltage Reference
INTERNAL VOLTAGE REFERENCE
1 1 1 1
1 1 1 1
0 0 0 0
1 1 1 1
0 0 0 0
0 0 0 0
1 1 1 1
1 1 1 1
0 0 0 0
1 1 1 1
0 0 0 0
0 0 0 0
OSR = 64 OUTPUT CODE EXAMPLES
OSR = 32 OUTPUT CODE EXAMPLES
ADC Output code (MSB First)
ADC Output code (MSB First)
1 1 1 1
1 1 1 1
0 0 0 0
1 1 1 1
0 0 0 0
0 0 0 0
1 1 1 1
1 1 1 1
0 0 0 0
1 1 1 1
0 0 0 0
0 0 0 0
1 1 1 1
1 1 1 1
0 0 0 0
1 1 1 1
0 0 0 0
0 0 0 0
1 1 1 1
1 1 1 1
0 0 0 0
1 1 1 1
0 0 0 0
0 0 0 0
REF
).
1 1 1 1
1 1 1 0
0 0 0 0
1 1 1 1
0 0 0 1
0 0 0 0
1 0 0 0
0 0 0 0
0 0 0 0
1 0 0 0
1 0 0 0
0 0 0 0
These bypass capacitors are not mandatory for correct
ADC operation, but removing these capacitors may
degrade accuracy of the ADC. The bypass capacitors
also help for applications where the voltage reference
output is connected to other circuits. In this case,
additional buffering may be needed as the output drive
capability of this output is low.
5.6.2
When the VREFEXT bit is high, the two reference pins
(REFIN+/OUT, REFIN-) become a differential voltage
reference input. The voltage at the REFIN+/OUT is
noted V
V
the following equation:
EQUATION 5-4:
The specified V
REFIN- pin voltage (V
Typically, for single-ended reference applications, the
REFIN- pin should be directly connected to AGND.
REF
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
-. The differential voltage input value is shown in
REF
+ and the voltage at the REFIN- pin is noted
DIFFERENTIAL EXTERNAL
VOLTAGE INPUTS
Hexadecimal
Hexadecimal
0x7FFFE0
0xFFFFF0
0x7FFFF0
0x800010
0x800000
REF
0x000000
0x7FFF80
0x7FFF00
0xFFFF80
0x800080
0x800000
V
0x000000
REF
range is from 2.2V to 2.6V. The
=V
REF
REF
-) should be limited to ±0.3V.
+ - V
MCP3903
REF
20-bit resolution
17-bit resolution
DS25048B-page 27
-
+ 524, 287
+ 524, 286
- 524, 288
- 524,287
+ 65, 535
+ 65, 534
Decimal
- 65, 536
Decimal
- 65,535
-1
-1
0
0