MAX1316 Datasheet, PDF (20/27 Pages) Maxim Integrated Products – 8-/4-/2-Channel, 14-Bit, Simultaneous-Sampling ADCs with 10V, 5V, and 0 to +5V Analog Input Ranges

8-/4-/2-Channel, 14-Bit, Simultaneous-Sampling ADCs
with ±10V, ±5V, and 0 to +5V Analog Input Ranges
No other digital system ground should be connected to
this single-point analog ground. The ground return to
the power supply for this ground should be low imped-
ance and as short as possible for noise-free operation.
High-frequency noise in the V_DD power supply may
affect the high-speed comparator in the ADC. Bypass
these supplies to the single-point analog ground with
0.1µF and 2.2µF bypass capacitors close to the device.
If the +5V power supply is very noisy, a ferrite bead can
be connected as a lowpass filter, as shown in Figure 8.
Transfer Functions
Bipolar ±10V Devices
Table 5 and Figure 9 show the two’s complement trans-
fer function for the MAX1324/MAX1325/MAX1326 with a
±10V input range. The full-scale input range (FSR) is
eight times the voltage at REF. The internal +2.500V ref-
erence gives a +20V FSR, while an external +2V to +3V
reference allows an FSR of +16V to +24V, respectively.
Calculate the LSB size using the following equation:
LSB
=
8 × V_REF
2¹⁴
This equals 1.2207mV with a +2.5V internal reference.
Table 5. ±10V Bipolar Code Table
The input range is centered about V_MSV. Normally,
MSV = AGND, and the input is symmetrical about zero.
For a custom midscale voltage, drive MSV with an
external voltage source. Noise present on MSV directly
couples into the ADC result. Use a precision, low-drift
voltage reference with adequate bypassing to prevent
MSV from degrading ADC performance. For maximum
FSR, be careful not to violate the absolute maximum
voltage ratings of the analog inputs when choosing
V_MSV.
Determine the input voltage as a function of V_REF,
V_MSV, and the output code in decimal using the follow-
ing equation:
V_{CH_} = LSB × CODE₁₀ + V_MSV
Bipolar ±5V Devices
Table 6 and Figure 10 show the two’s complement
transfer function for the MAX1320/MAX1321/MAX1322
with a ±5V input range. The FSR is four times the volt-
age at REF. The internal +2.500V reference gives a
+10V FSR, while an external +2V to +3V reference
allows an FSR of +8V to +12V, respectively. Calculate
the LSB size using the following equation:
LSB
=
4 × V_REF
2¹⁴
This equals 0.6104mV when using the internal reference.
TWO’S COMPLEMENT
BINARY OUTPUT CODE
01 1111 1111 1111
0x1FFF
01 1111 1111 1110
0x1FFE
00 0000 0000 0001
0x0001
00 0000 0000 0000
0x0000
11 1111 1111 1111
0x3FFF
10 0000 0000 0001
0x2001
10 0000 0000 0000
0x2000
DECIMAL
EQUIVALENT
OUTPUT
(CODE₁₀)
INPUT
VOLTAGE (V)
(V_REF = 2.5V,
V_MSV = 0V)
8191
9.9994
±0.5 LSB
8190
9.9982
±0.5 LSB
1
0.0018
±0.5 LSB
0
0.0006
±0.5 LSB
-1
-0.0006
±0.5 LSB
-8191
-9.9982
±0.5 LSB
-8192
-9.9994
±0.5 LSB
0x1FFF
0x1FFE
0x1FFD
0x1FFC
0x0001
0x0000
0x3FFF
8 x V_REF
8 x V_REF
0x2003
0x2002
0x2001
0x2000
1 LSB = ^{8 x VREF}
2¹⁴
-8192 -8190
-1 0 +1
(MSV)
+8189 +8191
INPUT VOLTAGE (V_{CH_} - V_MSV IN LSBs)
Figure 9. ±10V Bipolar Transfer Function
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