MAX11044_11 Datasheet, PDF (20/27 Pages) Maxim Integrated Products – 4-/6-/8-Channel, 16-/14-Bit, Simultaneous-Sampling ADCs

4-/6-/8-Channel, 16-/14-Bit,
Simultaneous-Sampling ADCs
Reference Buffer
The MAX11044/MAX11045/MAX11046 and MAX11054/
MAX11055/MAX11056 have a built-in reference buffer
to provide a low-impedance reference source to the
SAR converters. This buffer is used in both internal and
external reference mode. The reference buffer output
feeds five RDC pins. The RDC pins should be all con-
nected together on the PCB. The reference buffer is
externally compensated and requires at least 10µF on
the RDC node. For best performance, provide a total of
at least 80µF on the RDC outputs.
Transfer Functions
Figures 8 and 9 show the transfer functions for all the
formats and devices. Code transitions occur halfway
between successive-integer LSB values.
V_LSB = (10/4.096) x (V_REF/65,536)
7FFF +FS = 32,767 x V_LSB
7FFE
FULL-SCALE
TRANSITION
-FS = -32,768 x V_LSB
0001 OUTPUT CODE = ^VIN _{+ 32,768}
V_LSB
0000
FFFF
FFFE
8001
8000
-FS
0
+FS
-32,767.5 x V_LSB
+32,766.5 x V_LSB
INPUT VOLTAGE (LSB)
Figure 8. Two’s Complement Transfer Function for 16-Bit Devices
V_LSB = (10/4.096) x (V_REF/65,536)
FFFF ^{+FS = 32,767 x V}LSB
FFFE
FULL-SCALE
TRANSITION
-FS = -32,768 x V_LSB
8001
OUTPUT CODE =
V_IN
V_LSB
8000
7FFF
7FFE
0001
0000
-FS
0
+FS
-32,767.5 x V_LSB
+32,766.5 x V_LSB
INPUT VOLTAGE (LSB)
Figure 9. Offset-Binary Transfer Function for 16-Bit Devices
V_LSB = (10/4.096) x (V_REF/16,384)
1FFF +FS = 8191 x V_LSB
1FFE
FULL-SCALE
TRANSITION
-FS = -8192 x V_LSB
0001 OUTPUT CODE = ^VIN _{+ 8192}
V_LSB
0000
3FFF
3FFE
2001
2000
-FS
0
+FS
-8191.5 x V_LSB
+8190.5 x V_LSB
INPUT VOLTAGE (LSB)
Figure 8b. Two’s Complement Transfer Function for 14-Bit Devices
V_LSB = (10/4.096) x (V_REF/16,384)
3FFF +FS = 8191 x VLSB
3FFE
FULL-SCALE
TRANSITION
-FS = -8192 x V_LSB
2001 OUTPUT CODE = ^VIN
V_LSB
2000
1FFF
1FFE
0001
0000
-FS
0
+FS
-8191.5 x V_LSB
+8190.5 x V_LSB
INPUT VOLTAGE (LSB)
Figure 9b. Offset-Binary Transfer Function for 14-Bit Devices
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