19-4283; Rev 3; 3/11
Variable Reluctance Sensor Interfaces with
Differential Input and Adaptive Peak Threshold
General Description
The MAX9924–MAX9927 variable reluctance (VR or mag-
netic coil) sensor interface devices are ideal for position
and speed sensing for automotive crankshafts,
camshafts, transmission shafts, etc. These devices inte-
grate a precision amplifier and comparator with selectable
adaptive peak threshold and zero-crossing circuit blocks
that generate robust output pulses even in the presence
of substantial system noise or extremely weak VR signals.
The MAX9926/MAX9927 are dual versions of the
MAX9924/MAX9925, respectively. The MAX9924/
MAX9926 combine matched resistors with a CMOS input
precision operational amplifier to give high CMRR over a
wide range of input frequencies and temperatures. The
MAX9924/MAX9926 differential amplifiers provide a fixed
gain of 1V/V. The MAX9925/MAX9927 make all three ter-
minals of the internal operational amplifier available,
allowing greater flexibility for gain. The MAX9926 also
provides a direction output that is useful for quadrature-
connected VR sensors that are used in certain high-per-
formance engines. These devices interface with both
new-generation differential VR sensors as well as legacy
single-ended VR sensors.
The MAX9924/MAX9925 are available in the 10-pin
µMAX
®
package, while the MAX9926/MAX9927 are
available in the 16-pin QSOP package. All devices are
specified over the -40°C to +125°C automotive temper-
ature range.
Features
o
Differential Input Stage Provides Enhanced Noise
Immunity
o
Precision Amplifier and Comparator Allows
Small-Signal Detection
o
User-Enabled Internal Adaptive Peak Threshold or
Flexible External Threshold
o
Zero-Crossing Detection Provides Accurate
Phase Information
MAX9924–MAX9927
Ordering Information
PART
MAX9924UAUB+
MAX9925AUB+
MAX9926UAEE+
MAX9927AEE+
TEMP RANGE
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
PIN-PACKAGE
10 µMAX
10 µMAX
16 QSOP
16 QSOP
+Denotes
a lead(Pb)-free/RoHS-compliant package.
Selector Guide
PART
MAX9924UAUB
MAX9925AUB
MAX9926UAEE
MAX9927AEE
AMPLIFIER
1 x Differential
1 x Operational
2 x Differential
2 x Operational
GAIN
1V/V
Externally Set
1V/V
Externally Set
Applications
Camshaft VRS Interfaces
Crankshaft VRS Interfaces
Vehicle Speed VRS Interfaces
µMAX is a registered trademark of Maxim Integrated Products, Inc.
Simplified Block Diagram
ENGINE BLOCK
MAX9924
VR SENSOR
DIFFERENTIAL
AMPLIFIER
ADAPTIVE/MINIMUM
AND
ZERO-CROSSING
THRESHOLDS
INTERNAL/EXTERNAL
BIAS VOLTAGE
μC
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Variable Reluctance Sensor Interfaces with
Differential Input and Adaptive Peak Threshold
MAX9924–MAX9927
ABSOLUTE MAXIMUM RATINGS
V
CC
to GND .............................................................-0.3V to + 6V
All Other Pins..............................................-0.3V to (V
CC
+ 0.3V)
Current into IN+, IN-, IN_+, IN_-.......................................±40mA
Current into All Other Pins ................................................±20mA
Output Short-Circuit (OUT_, OUT) to GND.............................10s
Continuous Power Dissipation (T
A
= +70°C) (Note 1)
10-Pin µMAX (derate 8.8mW/°C above +70°C) ........707.3mW
16-Pin QSOP (derate 9.6mW/°C above +70°C)........771.5mW
Operating Temperature Range .........................-40°C to +125°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) .......................................+260°C
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.
PACKAGE THERMAL CHARACTERISTICS (Note 1)
µMAX
Junction-to-Ambient Thermal Resistance (θ
JA
) ......113.1°C/W
Junction-to-Case Thermal Resistance (θ
JC
) ................42°C/W
QSOP
Junction-to-Ambient Thermal Resistance (θ
JA
) ......103.7°C/W
Junction-to-Case Thermal Resistance (θ
JC
) ................37°C/W
Note 1:
Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to
www.maxim-ic.com/thermal-tutorial.
ELECTRICAL CHARACTERISTICS
(V
CC
= 5V, V
GND
= 0V, MAX9925/MAX9927 gain setting = 1V/V, Mode A1, V
BIAS
= 2.5V, V
PULLUP
= 5V, R
PULLUP
= 1kΩ, C
COUT
=
50pF. T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 2)
PARAMETER
POWER SUPPLY
Operating Supply Range
Supply Current
Power-On Time
V
CC
I
CC
P
ON
(Note 3)
MAX9924/MAX9925
MAX9926/MAX9927
V
CC
> V
UVLO
= 4.1V, step time for V
CC
~ 1µs
Guaranteed by CMRR
Temperature drift
0.5
(Note 4)
(Note 4)
From V
CM
= 0 to V
CC
MAX9925
MAX9927
Output Voltage Low
Output Voltage High
Recovery Time from Saturation
Gain-Bandwidth Product
Slew Rate
Charge-Pump Frequency
V
OL
V
OH
t
SAT
GBW
SR
f
CP
I
OL
= 1mA
I
OH
= -1mA
To 1% of the actual V
OUT
after output
saturates
V
CC
-
0.050
1.2
1.4
2.3
1.3
75
88
77
0.1
0.05
102
105
94
0.050
V
V
µs
MHz
V/µs
MHz
0
4.5
2.6
4.7
30
5.5
5
10
150
V
mA
µs
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
INPUT OPERATIONAL AMPLIFIER (MAX9925/MAX9927)
Input Voltage Range
Input Offset Voltage
Input Bias Current
Input Offset Current
Common-Mode Rejection Ratio
Power-Supply Rejection Ratio
IN+, IN-
V
OS-OA
I
BIAS
I
OFFSET
CMRR
PSRR
V
CC
5
3
6
2
V
µV/°C
mV
nA
nA
dB
dB
2
_______________________________________________________________________________________
Variable Reluctance Sensor Interfaces with
Differential Input and Adaptive Peak Threshold
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 5V, V
GND
= 0V, MAX9925/MAX9927 gain setting = 1V/V, Mode A1, V
BIAS
= 2.5V, V
PULLUP
= 5V, R
PULLUP
= 1kΩ, C
COUT
=
50pF. T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
V
CC
+
0.3
87
78
100
135
UNITS
MAX9924–MAX9927
INPUT DIFFERENTIAL AMPLIFIER (MAX9924/MAX9926)
Input Voltage Range
Differential Amplifier
Common-Mode Rejection Ratio
Input Resistance
ADAPTIVE PEAK DETECTION
Mode B
operation
(Notes 5, 6)
MAX9924/MAX9925
MAX9926/MAX9927
-6.5
-6.5
0
0
33
4
15
30
+6.5
mV
+10
%PK
IN+, IN-
CMRR
R
IN
Guaranteed by CMRR
MAX9924 (Note 5)
MAX9926 (Note 5)
(Note 5)
-0.3
60
55
65
V
dB
kΩ
Zero-Crossing Threshold
V
ZERO_THRESH
V
ADAPTIVE
Adaptive peak threshold
Minimum threshold of hysteresis
comparator MAX9924/MAX9926
(Notes 5, 6)
Minimum threshold of hysteresis
comparator MAX9925/MAX9927
(Notes 5, 6)
20
30
50
mV
Fixed and Adaptive Peak
Threshold
V
MIN-THRESH
V
MIN-THRESH
- V
ZERO-THRESH
for
MAX9924 (Notes 5, 6)
V
MIN-THRESH
- V
ZERO-THRESH
for
MAX9926 (Notes 5, 6)
V
MIN-THRESH
- V
ZERO-THRESH
for
MAX9925/MAX9927 (Notes 5, 6)
7
2
19
15
15
30
26
30
50
Watchdog Timeout for Adaptive
Peak Threshold
ENTIRE SYSTEM
Comparator Output Low Voltage
Propagation Delay
COUT Transition Time
Propagation Delay Jitter
t
WD
Timing window to reset the adaptive
peak threshold if not triggered (input
level below threshold)
45
85
140
ms
V
COUT_OL
t
PDZ
t
PDA
t
HL-LH
t
PD-JITTER
Includes noise of differential amplifier
and comparator, f = 10kHz,
V
IN
= 1V
P-P
sine wave
Overdrive = 2V to 3V, zero-crossing
Overdrive = 2V to 3V, adaptive peak
50
150
2
20
0.2
V
ns
ns
ns
_______________________________________________________________________________________
3
Variable Reluctance Sensor Interfaces with
Differential Input and Adaptive Peak Threshold
MAX9924–MAX9927
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 5V, V
GND
= 0V, MAX9925/MAX9927 gain setting = 1V/V, Mode A1, V
BIAS
= 2.5V, V
PULLUP
= 5V, R
PULLUP
= 1kΩ, C
COUT
=
50pF. T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 2)
PARAMETER
EXT
Mode B, T
A
= +125°C
EXT Voltage Range
V
EXT
Mode C, T
A
= +125°C
Input Current to EXT
DIRN (MAX9926 Only)
Output Low Voltage
INT_THRS, ZERO_EN
Low Input
High Input
Input Leakage
Input Current ZERO_EN
Switching Time Between Modes
A1, A2, and Modes B, C
BIAS
Input Current to BIAS
I
BIAS
Modes A1, A2, B, C
Modes A1, B, T
A
= +125°C
BIAS Voltage Range
V
BIAS
Mode C, T
A
= +125°C
Internal BIAS Reference Voltage
V
INT_BIAS
Mode A2 (MAX9924/MAX9926)
0.2
2.46
1.5
1
V
CC
- 1.1
V
CC
- 1.1
V
µA
V
IL
V
IH
I
LEAK
I
SINK
Pullup resistor = 10kΩ,
V
ZERO_EN
= V
GND
With INT_THRS = GND, auto peak-
detect is disabled, and EXT_THRS is
active
500
0.7 x
V
CC
1
800
0.3 x
V
CC
V
V
µA
µA
0.2
V
I
EXT
Mode B, V
EXT
> V
BIAS
; and Mode C
0.14
1.5
V
CC
- 1.1
V
V
CC
- 1.1
10
µA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
t
SW
3
µs
V
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Specifications are 100% tested at T
A
= +125°C, unless otherwise noted. All temperature limits are guaranteed by design.
Inferred from functional PSRR.
CMOS inputs.
Guaranteed by design.
Includes effect of V
OS
of internal op amp and comparator.
4
_______________________________________________________________________________________
Variable Reluctance Sensor Interfaces with
Differential Input and Adaptive Peak Threshold
Typical Operating Characteristics
(V
CC
= 5V, V
GND
= 0V, MAX9925/MAX9927 gain setting = 1V/V. All values are at T
A
= +25°C, unless otherwise noted.)
INPUT OFFSET VOLTAGE
vs. INPUT COMMON-MODE VOLTAGE
MAX9924 toc01
MAX9924 toc02
MAX9924–MAX9927
INPUT OFFSET VOLTAGE DISTRIBUTION
20
V
CM
= 0
BIN SIZE = 250
PERCENTAGE OF UNITS (%)
15
0.5
COMMON-MODE REJECTION RATIO
vs. FREQUENCY
MAX9924 toc03
120
100
80
CMRR (dB)
INPUT OFFSET VOLTAGE (mV)
0.4
0.3
10
60
40
0.2
5
0.1
V
OUT
= 2.5V
MAX9925
20
0
1
0
0
2000 3000
-2000 -1000
1000
-500
500
1500 2500
-1500
INPUT OFFSET VOLTAGE (μV)
0
-0.5
0.5
1.5
2.5
3.5
4.5
5.5
INPUT COMMON-MODE VOLTAGE (V)
V
BIAS
= V
OUT
= 2.5V
V
CM
= 2V
P-P
CMRR = 20log(A
DM
/A
CM
)
10
100
1k
10k
100k
FREQUENCY (Hz)
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX9924 toc04
OPEN LOOP FREQUENCY
RESPONSE
V
CC
= 5V
V
BIAS
= 2.5V
V
OUT
= 2V
P-P
MAX9925
MAX9924 toc05
V
OL
AND V
OH
vs. TEMPERATURE
35
30
V
OL
AND V
OH
(mV)
25
V
CC
- V
OH
20
15
10
V
OL
MAX9924 toc06
0
-10
-20
-30
PSSR (dB)
-40
-50
-60
-70
-80
-90
-100
-110
-120
1
V
RIPPLE
= 100mV
P-P
V
BIAS
= V
OUT
= 2.5V
INPUTS COUPLED TO GND
125
40
100
GAIN (dB)
75
50
25
5
10
100
1k
10k
100k
0
0.001
0
0.1
FREQUENCY (kHz)
10
-50
-25
0
25
50
75
100
125
TEMPERATURE (°C)
FREQUENCY (Hz)
INPUT OFFSET VOLTAGE
vs. TEMPERATURE
MAX9924 toc07
ADAPTIVE THRESHOLD AND RATIO
vs. SIGNAL LEVEL
MAX9924 toc08
ADAPTIVE THRESHOLD
vs. TEMPERATURE
350
300
THRESHOLD (mV)
250
200
150
100
V
IN
= 2V
P-P
f
IN
= 1kHz
MAX9924
-50
-25
0
25
50
75
100
125
MAX9924 toc09
0.6
0.5
0.4
0.3
V
CM
= 2.5V
0.2
0.1
0
-50
-25
0
25
50
ADAPTIVE THRESHOLD LEVEL (mV)
V
OUT
= 2.5V
MAX9925
900
800
700
600
500
400
300
200
100
0
f
IN
= 1kHz
MAX9924
0
0.5
1.0
1.5
2.0
400
INPUT OFFSET VOLTAGE (mV)
V
CM
= 0
50
0
2.5
TEMPERATURE (°C)
75
100
125
TEMPERATURE (°C)
SIGNAL LEVEL (V
P
)
_______________________________________________________________________________________
5
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