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19-2229; Rev 1; 7/03
Digitally Programmable Precision Voltage Divider for PGAs
General Description
The MAX5420 and MAX5421 are digitally programmable precision voltage dividers optimized for use in digitally programmable gain amplifier configurations. The MAX5420/ MAX5421 operate from a single +5V supply or dual 5V supply, and consume only 3A supply current. These devices consist of a digitally selectable resistor array that provides four precision noninverting gains of 1, 2, 4, and 8 for PGAs. The MAX5420 and MAX5421 achieve a resistor ratio accuracy of 0.025% (MAX542_A), 0.09% (MAX542_B), and 0.5% (MAX542_C). The MAX5421 includes an on-chip matching resistor for op amp bias-current compensation. The MAX5420 and MAX5421 are available in 8-pin and 10-pin MAX packages. The devices are specified over the extended temperature range (-40C to +85C).
Features
o Four Precision Divider Ratios For Noninverting Gains of 1, 2, 4, and 8 in PGAs o 0.025%, 0.09%, or 0.5% Ratio Accuracy Guaranteed Over -40C to +85C o On-Chip Matching Resistor for Op Amp BiasCurrent Compensation (MAX5421) o 5V Single or 5V Dual Supply Operation o Low 3A Supply Current o CMOS/TTL Logic Compatible 2-Wire Parallel Interface o Small 8-Pin and 10-Pin MAX Packages
MAX5420/MAX5421
Applications
General-Purpose Programmable Noninverting Amplifiers Programmable Instrumentation Amplifiers
Ordering Information
PART TEMP RANGE -40C to +85C PINPACKAGE 8 MAX 8 MAX 8 MAX 10 MAX 10 MAX 10 MAX GAIN ACCURACY 0.025% 0.09% 0.5% 0.025% 0.09% 0.5%
MAX5420AEUA -40C to +85C MAX5420BEUA MAX5420CEUA -40C to +85C MAX5421AEUB -40C to +85C MAX5421BEUB -40C to +85C MAX5421CEUB -40C to +85C
Functional Diagram
TOP VIEW
VDD 1 2
Pin Configurations
8 7
H W L D1
VDD MAX5420 MAX5421 D0 DECODER D1 MATCH_H MATCH_L
H
VSS GND
MAX5420
3 6 5
W
D0 4
MAX-8
VDD 1
10 H 9 W L MATCH_H MATCH_L
VSS GND L MAX5421 ONLY
VSS GND D0 D1
2 3 4 5
MAX5421
8 7 6
MAX-10
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
Digitally Programmable Precision Voltage Divider for PGAs MAX5420/MAX5421
ABSOLUTE MAXIMUM RATINGS
VDD to GND ..............................................................-0.3V to +6V VSS to GND...............................................................+0.3V to -6V D0, D1 to GND ...........................................-0.3V to (VDD + 0.3V) H, L, W, MATCH_ to GND ................(VSS - 0.3V) to (VDD + 0.3V) Input and Output Latchup Immunity.................................50mA Continuous Power Dissipation (TA = +70C) 8-Pin MAX (derate 4.1mW/C above +70C) .............333mW 10-Pin MAX (derate 5.6mW/C above +70C) ...........444mW Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-60C to +150C Lead Temperature (soldering, 10s) .................................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VDD = +5V 5%, VSS = -5V 5% or VSS = GND, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER Divider Ratio Accuracy H-to-L Resistance Input Resistance at H Input Resistance at W Capacitance at H, L, W, MATCH_H, MATCH_L Matching Resistor DYNAMIC PERFORMANCE Switching Time DIGITAL INPUTS Input High Voltage Input Low Voltage Input Leakage Current Input Capacitance VIH VIL D1, D0 = VDD or GND 5 2.4 0.8 1 V A pF tS VDD = +5V, VSS = -5V, digital input 0 to +3V, VW settles to 0.02% of final value with 2pF capacitive load. Circuit of Figure 2. 0.5 s RHL RH RW Ratio = 1 Ratio = 2, 4, 8 CANALOG Ratio = 1 Ratio = 2, 4, 8 VSS = -5V VSS = 0 VSS = -5V VSS = 0 SYMBOL MAX542_A MAX542_B MAX542_C (Figure 1) 15 15 300 500 8 5 300 500 8 CONDITIONS MIN TYP MAX 0.025 0.09 0.5 k k k pF k % UNITS
MAX5421
2
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Digitally Programmable Precision Voltage Divider for PGAs
ELECTRICAL CHARACTERISTICS (continued)
(VDD = +5V 5%, VSS = -5V 5% or VSS = GND, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER POWER SUPPLIES Positive Supply Voltage Negative Supply Voltage Positive Supply Current Negative Supply Current W, H, L, MATCH_L, MATCH_H Voltage Range VDD VSS IDD ISS D1, D0 = VDD or GND D1, D0 = 3V D1, D0 = VDD or GND D1, D0 = 3V VSS 4.75 0 3 15 3 15 5.25 -5.25 7 25 7 25 VDD V A A V SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX5420/MAX5421
Typical Operating Characteristics
(VDD = +5V, VSS = -5V, or VSS = GND, TA = +25C, unless otherwise noted.) (Note 1)
MAX542_A DIVIDER RATIO ACCURACY vs. TEMPERATURE
MAX5420/21 toc01
MAX542_A DIVIDER RATIO ACCURACY vs. TEMPERATURE
MAX5420/21 toc02
MAX542_A DIVIDER RATIO ACCURACY vs. TEMPERATURE
VH = +5V VL = -5V RATIO = 4
MAX5420/21 toc03
0.0010 VH = +5V VL = -5V RATIO = 1 RATIO ACCURACY (%) 0.0007
0.0050 VH = +5V VL = -5V RATIO = 2
0.005
0.0046 RATIO ACCURACY (%)
0.004 RATIO ACCURACY (%)
0.0042
0.003
0.0038
0.002
0.0004
0.0034
0.001
0.0001 -40 -15 10 35 60 85 TEMPERATURE (C)
0.0030 -40 -15 10 35 60 85 TEMPERATURE (C)
0 -40 -15 10 35 60 85 TEMPERATURE (C)
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3
Digitally Programmable Precision Voltage Divider for PGAs MAX5420/MAX5421
Typical Operating Characteristics (continued)
(VDD = +5V, VSS = -5V, or VSS = GND, TA = +25C, unless otherwise noted.) (Note 1)
MAX542_A DIVIDER RATIO ACCURACY vs. TEMPERATURE
MAX5420/21 toc04
MAX542_B DIVIDER RATIO ACCURACY vs. TEMPERATURE
MAX5420/21 toc05
MAX542_B DIVIDER RATIO ACCURACY vs. TEMPERATURE
VH = +5V VL = -5V RATIO = 2 RATIO ACCURACY (%) -0.0225
MAX5420/21 toc06
0.007 0.006 RATIO ACCURACY (%) 0.005 0.004 0.003 0.002 0.001 0 -40 -15 10 35 60 VH = +5V VL = -5V RATIO = 8
0.0020 VH = +5V VL = -5V RATIO = 1 RATIO ACCURACY (%) 0.0015
-0.0200
0.0010
-0.0250
0.0005
-0.0275
0 85 -40 -15 10 35 60 85 TEMPERATURE (C) TEMPERATURE (C)
-0.0300 -40
-15
10
35
60
85
TEMPERATURE (C)
MAX542_B DIVIDER RATIO ACCURACY vs. TEMPERATURE
MAX5420/21 toc07
MAX542_B DIVIDER RATIO ACCURACY vs. TEMPERATURE
VH = +5V VL = -5V RATIO = 8 RATIO ACCURACY (%) -0.055
MAX5420/21 toc08
MAX542_A RATIO ACCURACY vs. POSITIVE SUPPLY VOLTAGE
RATIO = 4 RATIO ACCURACY (%)
MAX5420/21 toc09
-0.030 VH = +5V VL = -5V RATIO = 4 RATIO ACCURACY (%) -0.035
-0.050
0.01
RATIO = 2 0.001
RATIO = 8
-0.040
-0.060
-0.045
-0.065 RATIO = 1 VH = +3V, VL = 0
-0.050 -40 -15 10 35 60 85 TEMPERATURE (C)
-0.070 -40 -15 10 35 60 85 TEMPERATURE (C)
0.0001 4.75 5.00 POSITIVE SUPPLY VOLTAGE (V) 5.25
MAX542_B RATIO ACCURACY vs. POSITIVE SUPPLY VOLTAGE
MAX5420/21 toc10
MAX542_A RATIO ACCURACY vs. NEGATIVE SUPPLY VOLTAGE
MAX5420/21 toc11
MAX542_B RATIO ACCURACY vs. NEGATIVE SUPPLY VOLTAGE
RATIO = 4
MAX5420/21 toc12
0.1
RATIO = 4
0.01
RATIO = 8
0.1
RATIO ACCURACY (%)
RATIO ACCURACY (%)
0.01 RATIO = 8 0.001
RATIO = 2
RATIO ACCURACY (%)
RATIO = 2 0.01 RATIO = 8 VH = 5V, VL = 0 0.001
RATIO = 4 0.001
RATIO = 2
RATIO = 1 0.0001 VH = +3V, VL = 0 4.75 5.00 POSITIVE SUPPLY VOLTAGE (V) RATIO = 1 5.25 VH = 5V, VL = 0 0.0001 -5.25 -4.00 -2.75 -1.50 -0.25 0.0001 -5.25 -4.00 RATIO = 1 -2.75 -1.50 -0.25
NEGATIVE SUPPLY VOLTAGE (V)
NEGATIVE SUPPLY VOLTAGE (V)
4
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Digitally Programmable Precision Voltage Divider for PGAs MAX5420/MAX5421
Typical Operating Characteristics (continued)
(VDD = +5V, VSS = -5V, or VSS = GND, TA = +25C, unless otherwise noted.) (Note 1)
SWITCHING TIME (RATIO 1-TO-2)
MAX5420/21 toc13
SWITCHING TIME (RATIO 2-TO-4)
MAX5420/21 toc14
D0, 5V/div 0
D1, 5V/div 0
VW 2V/div
VW 1V/div
100ns/div VH = +5V, VL = -5V
100ns/div VH = +5V, VL = -5V
SWITCHING TIME (RATIO 4-TO-8)
MAX5420/21 toc15
SUPPLY CURRENT vs. TEMPERATURE
D1, D0 = GND or VDD 5V D0, 5V/div 0 4 SUPPLY CURRENT (A)
MAX5420/21 toc16
5
3
VW 500mV/div
2
1
0 100ns/div VH = +5V, VL = -5V -40 -15 10 35 60 85 TEMPERATURE (C)
Note 1: For MAX542_C accuracy Typical Operating Characteristics, refer to MAX542_B accuracy Typical Operating Characteristics.
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5
Digitally Programmable Precision Voltage Divider for PGAs MAX5420/MAX5421
Pin Description
PIN MAX5420 1 2 3 4, 5 6 7 8 -- -- MAX5421 1 2 3 4, 5 8 9 10 6 7 VDD VSS GND D0, D1 L W H MATCH_L MATCH_H Positive Supply Voltage Negative Supply Voltage Ground Digital Control Inputs. Drive D0 and D1 logic high or logic low to set the divider ratio. See Logic Control Truth Table. Low Terminal of Resistor-Divider Resistor-Divider Output High Terminal of Resistor-Divider Matching Resistor Low Terminal Matching Resistor High Terminal NAME FUNCTION
Detailed Description
The MAX5420/MAX5421 are digitally programmable precision voltage dividers for programmable-gain amplifiers. Operationally, these devices consist of digitally selectable precision resistor-dividers providing noninverting gains of 1, 2, 4, and 8 for PGA applications (see Functional Diagram and Figure 1). Ratio = 1 + R_B R_ A
Table 1. Logic Control Truth Table
DIGITAL INPUTS D1 0 0 1 1 D0 0 1 0 1 DIVIDER RATIO 1 2 4 8
Digital Interface Operation
The MAX5420/MAX5421 feature a simple two-bit parallel programming interface. D1 and D0 program the divider ratio setting according to the Logic Control Truth Table (Table 1). The digital interface is CMOS/TTL logic compatible.
The MAX5420/MAX5421 achieve divider ratio accuracy of 0.025% (MAX5420A/MAX5421A), 0.09% (MAX5420B/ MAX5421B) or 0.5% (MAX5420C/MAX5421C). The end-to-end resistance from H to L is 15k. The impedance seen at W is designed to be the same 8k for divider ratios 2, 4, and 8, ensuring excellent impedance matching and constant switching times. In gain of +1 configuration, H is internally connected to W with a typical resistance of 500.
Applications Information
Programmable-Gain Amplifier
The MAX5420/MAX5421 are ideally suited for high-precision PGA applications. The typical application circuit of Figure 3 uses the MAX5421 with matching resistor to compensate for voltage offset due to op amp input bias currents. Use the MAX5420 with an ultra-low input bias current op amp such as the MAX4237 (Figure 4).
Matching Resistor (MAX5421)
The MAX5421 includes a matching resistor to compensate for offset voltage due to input bias current of the op amp. The resistance from MATCH_H to MATCH_L, equals the resistance seen at W for gains of 2, 4, and 8. In the gain of +1, an internal switch connects MATCH_H and MATCH_L. This internal switch matches the impedance of the switch between H and W.
Power Supplies and Bypassing
The MAX5420/MAX5421 operate from dual 5V supplies, or a single +5V supply. For dual supplies, bypass VDD and VSS with 0.1F ceramic capacitors to GND. For single supply, connect VSS to GND and bypass VDD with a 0.1F ceramic capacitor to GND.
6
_______________________________________________________________________________________
Digitally Programmable Precision Voltage Divider for PGAs MAX5420/MAX5421
H RATIO = 1
+5V VDD MATCH_H VIN MAX5421 L H
MAX4493
+5V MATCH_L VOUT
R3B
R2B
R1B RATIO = 2
GND VSS W
RATIO = 4 RATIO = 8 W
Figure 3. Programmable-Gain Amplifier with Op Amp BiasCurrent Matching
R3A
R2A
R1A
+5V VIN
MAX4237
RATIO = 1+
(
R_B R_A
)
+5V
VOUT
L
Figure 1. Simplified Functional Diagram
VDD
+5V
W H
0.1F
MAX5420
VDD H RATIO = 1
VSS
L
GND
R3B
R2B
R1B RATIO = 2
Figure 4. Programmable-Gain Amplifier
RATIO = 4 RATIO = 8 W RATIO = 1+ R3A R2A R1A TEKTRONIX P6245 OSCILLOSCOPE FET PROBE CL < 1pF 1M
Switching Time and Layout Concerns
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.
(
R_B R_A
)
MAX5421
VSS 0.1F -5V GND PULSE GENERATOR L D1 D0
Chip Information
TRANSISTOR COUNT: 118 PROCESS: CMOS
Figure 2. Switching Time Test Circuit
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7
Digitally Programmable Precision Voltage Divider for PGAs MAX5420/MAX5421
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
8LUMAXD.EPS
4X S
8
8
INCHES DIM A A1 A2 b MIN 0.002 0.030 MAX 0.043 0.006 0.037
MILLIMETERS MAX MIN 0.05 0.75 1.10 0.15 0.95
y 0.500.1
E
H
0.60.1
c D e E H L
1
1
0.60.1
S
D
BOTTOM VIEW
0.014 0.010 0.007 0.005 0.120 0.116 0.0256 BSC 0.120 0.116 0.198 0.188 0.026 0.016 6 0 0.0207 BSC
0.25 0.36 0.13 0.18 2.95 3.05 0.65 BSC 2.95 3.05 4.78 5.03 0.41 0.66 0 6 0.5250 BSC
TOP VIEW
A2
A1
A
c e b L
SIDE VIEW
FRONT VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, 8L uMAX/uSOP
APPROVAL DOCUMENT CONTROL NO. REV.
21-0036
1 1
J
8
_______________________________________________________________________________________
Digitally Programmable Precision Voltage Divider for PGAs
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
10LUMAX.EPS
MAX5420/MAX5421
e
10
4X S
10
INCHES MAX DIM MIN 0.043 A 0.006 A1 0.002 A2 0.030 0.037 D1 0.116 0.120 0.114 0.118 D2 0.116 E1 0.120 E2 0.114 0.118 H 0.187 0.199 L 0.0157 0.0275 L1 0.037 REF b 0.007 0.0106 e 0.0197 BSC c 0.0035 0.0078 0.0196 REF S 0 6
MILLIMETERS MAX MIN 1.10 0.15 0.05 0.75 0.95 3.05 2.95 3.00 2.89 3.05 2.95 2.89 3.00 4.75 5.05 0.40 0.70 0.940 REF 0.177 0.270 0.500 BSC 0.090 0.200 0.498 REF 0 6
H y 0.500.1 0.60.1
1
1
0.60.1
TOP VIEW
BOTTOM VIEW
D2 GAGE PLANE A2 A b A1 D1
E2
c
E1 L1
L
FRONT VIEW
SIDE VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, 10L uMAX/uSOP
APPROVAL DOCUMENT CONTROL NO. REV.
21-0061
1 1
I
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 9 (c) 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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