MAX154 Datasheet, PDF (10/12 Pages) Maxim Integrated Products – CMOS High-Speed 8-Bit ADCs with Multiplexer and Reference

CMOS High-Speed 8-Bit ADCs with
Multiplexer and Reference
Bipolar Input Operation
The circuit in Figure 10a can be used for bipolar input
operation. The input voltage is scaled by an amplifier
so that only positive voltages appear at the ADC’s
inputs. The analog input range is ±4V and the output
code is complementary offset binary. The ideal
input/output characteristic is shown in Figure 10b.
RS _AIN1
VIN
RMUX
CS
12pF
CS
2pF
RON
1pF
TO LS
•
1pF
LADDER
•
•
15 LSB COMPARATORS
RON
1pF
TO MS
LADDER
• 1pF
•
•
16 MSB COMPARATORS
Figure 9a. Equivalent Input Circuit
R_{S AIN1}
B MUX
600Ω
R_ON
350Ω
V_IN
C_S1
2pF
C_S2
2pF
32pF
Figure 9b. RC Network Model
11.5Ω
V_IN
3.57k
10.0k
0.01µF
16.2k
+5V
0.1µF
0.01µF
47µF
AIN1
CS
MAX154 RDY
MAX158
RD
V_REF+
INT
REFOUT
V_DD
V_REF-
GND
DB0-DB7
11111111
11111110
11111101
10000010
10000001
10000000
01111111
01111110
00000010
00000001
00000000
-FS _{+ 1LSB}
2
FS = 8V
1LSB = FS / 256
+FS
2
0V
AIN INPUT VOLTAGE (LSBs)
Figure 10b. Transfer Function for ±4V Input Operation
A15
ADDRESS BUS
A0
MREQ
ZBO
WAIT
RD
ADDRESS
EN DECODE
5V
5k
D0-D7
DATA BUS
A0 A1 A2*
CS ^MAX154
MAX158
RDY
RD
DB0-DB7
*A2 ON MAX158.
ONLY CHANNEL 1 SHOWN
Figure 10a. Bipolar ±4V Input Operation
Figure 11. Simple Mode 0 Interface
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