MAX1213_09 Datasheet, PDF (13/19 Pages) Maxim Integrated Products – 1.8V, 12-Bit, 170Msps ADC for Broadband Applications

1.8V, 12-Bit, 170Msps ADC for
Broadband Applications
Table 1. MAX1213 Digital Output Coding
INP ANALOG
INPUT VOLTAGE
LEVEL
> V_CM + V_FS / 4
V_CM + V_FS / 4
V_CM
V_CM - V_FS / 4
< V_CM + V_FS / 4
INN ANALOG
INPUT VOLTAGE
LEVEL
< V_CM - V_FS / 4
V_CM - V_FS / 4
V_CM
V_CM + V_FS / 4
> V_CM - V_FS / 4
OUT-OF-RANGE
ORP (ORN)
BINARY DIGITAL OUTPUT
CODE (D11P/N–D0P/N)
1 (0)
0 (1)
0 (1)
0 (1)
1 (0)
1111 1111 1111
(exceeds +FS, OR set)
1111 1111 1111 (+FS)
1000 0000 0000 or
0111 1111 1111 (FS/2)
0000 0000 0000 (-FS)
00 0000 0000
(exceeds -FS, OR set)
TWO’S COMPLEMENT DIGITAL
OUTPUT CODE (D11P/N–D0P/N)
0111 1111 1111
(exceeds +FS, OR set)
0111 1111 1111 (+FS)
0000 0000 0000 or
1111 1111 1111 (FS/2)
1000 0000 0000 (-FS)
10 0000 0000
(exceeds -FS, OR set)
OV_CC
V_OP
2.2kΩ
V_ON
2.2kΩ
ADC FULL SCALE = REFT-REFB
REFT
G
REFERENCE
SCALING
AMPLIFIER
REFERENCE ^REFB
BUFFER
1V
REFIO
CONTROL LINE
TO DISABLE
REFERENCE BUFFER
REFADJ
0.1μF
13kΩ TO
1MΩ
13kΩ TO
1MΩ
OGND
Figure 5. Simplified LVDS Output Architecture
Applications Information
FSR Adjustments Using the Internal
Bandgap Reference
The MAX1213 supports a full-scale adjustment range of
10% (±5%). To decrease the full-scale signal range, an
external resistor value ranging from 13kΩ to 1MΩ may
be added between REFADJ and AGND. A similar
approach can be taken to increase the ADC’s full-scale
range (FSR). Adding a variable resistor, potentiometer,
or predetermined resistor value between REFADJ and
REFIO increases the FSR of the data converter. Figure
6a shows the two possible configurations and their
impact on the overall full-scale range adjustment of the
MAX1213. Do not use resistor values of less than 13kΩ
to avoid instability of the internal gain regulation loop
for the bandgap reference. See Figure 6b for the
results of the adjustment range for a selection of resis-
tors used to trim the full-scale range of the MAX1213.
MAX1213
AV_CC
REFT: TOP OF REFERENCE LADDER.
REFB: BOTTOM OF REFERENCE LADDER.
AV_CC/2
Figure 6a: Circuit Suggestions to Adjust the ADC’s Full-Scale
Range
FS VOLTAGE vs. FS ADJUST RESISTOR
1.57
1.55
1.53
RESISTOR VALUE APPLIED BETWEEN
1.51
REFADJ AND REFIO INCREASES V_FS
1.49
1.47
1.45
1.43
RESISTOR VALUE APPLIED BETWEEN
1.41
REFADJ AND AGND DECREASES V_FS
1.39
1.37
0
125 250 375 500 625 750 875 1000
FS ADJUST RESISTOR (kΩ)
Figure 6b: FS Adjustment Range vs. FS Adjustment Resistor
______________________________________________________________________________________ 13