MAX5420 MAXIM [Maxim Integrated Products], MAX5420 Datasheet - Page 7

• Manufacturer Part Number: MAX5420
• Description: Digitally Programmable Precision Voltage Divider for PGAs
• Manufacturer: MAXIM [Maxim Integrated Products]

Figure 1. Simplified Functional Diagram
Figure 2. Switching Time Test Circuit
GND
R3B
R3A
0.1 F
RATIO = 8
0.1 F
+5V
-5V
V
V
R3B
R3A
DD
SS
RATIO = 8
H
L
R2B
R2A
_______________________________________________________________________________________
RATIO = 4
GENERATOR
PULSE
H
L
R2A
R2B
RATIO = 4
R1A
R1B
RATIO =
MAX5421
RATIO = 2
RATIO = 1
D1
(
1+
R_B
R_A
R1A
R1B
RATIO =
D0
Digitally Programmable Precision
)
RATIO = 2
RATIO = 1
W
(
1+
R_B
R_A
OSCILLOSCOPE FET
)
TEKTRONIX P6245
C
PROBE
L
1M
< 1pF
W
Voltage Divider for PGAs
Figure 4. Programmable-Gain Amplifier
The switching time of the MAX5420/MAX5421 depends
on the capacitive loading at W. For best performance,
reduce parasitic board capacitance by minimizing the
circuit board trace from W to the op amp inverting input,
and choose an op amp with low input capacitance.
TRANSISTOR COUNT: 118
PROCESS: CMOS
Figure 3. Programmable-Gain Amplifier with Op Amp Bias-
Current Matching
V
IN
MATCH_H
Switching Time and Layout Concerns
V
SS
GND
+5V
L
V
DD
L
V
SS
+5V
MAX5421
V
W
DD
GND
W
V
MAX5420
IN
H
MATCH_L
Chip Information
MAX4237
H
+5V
MAX4493
+5V
V
OUT
V
OUT
7