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MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
General Description
Benefits and Features
The MAX40056 is a bidirectional current-sense amplifier
with an input common-mode range that extends from
-0.1V to +65V together with protection against negative inductive kickback voltages to -5V. This CSA is well-suited
for phase current monitoring of inductive loads, such as
motors and solenoids, where pulse width modulation is
used to control the drive voltage and current. The
MAX40056 uses an improved technique to help reject
common-mode input PWM edges with slew rates up to
and beyond ±500V/µs. Common mode rejection ratio
(CMRR) is typically 60dB (50V, ±500V/µs input) and
140dB DC, typical.
● AEC-Q100
● Fast, 500ns PWM Edge Recovery from 500V/μs PWM
Edges
● 60dB AC CMRR Rejection at 50V, ±500V/μs PWM
Edges
● 140dB DC CMRR Rejection
● -0.1V to +65V Input Voltage Range
● -5V to +70V Protective Immunity
● 300kHz, -3dB Bandwidth
● Multiple Gain Options; 10V/V, 20V/V, 50V/V
● Internal, 1% Reference for Bidirectional Offset
● 5μV (Typ) Input Offset Voltage
● Rail-to-Rail Output
● 2.02mm x 1.4mm, 8-bump WLP and 8-pin μMAX
● -40°C to +125°C Temperature Range
The MAX40056 has an internal +1.5V reference for use
with a nominal +3.3V power supply. The reference can also be used to drive an adjoining differential ADC. The reference is used to offset the output to indicate the direction of the input sensed current. The REF pin can source
current into external loads and helps to avoid the performance compromises resulting from routing reference voltages across noisy PCBs. Alternatively, for higher supply
voltages and higher full-scale output swings, the internal
reference can be overridden by a higher voltage, external
reference.
The internal or external reference can be used to define
the trip threshold for the integrated overcurrent comparator. This can provide immediate indication of an overcurrent fault condition.
The MAX40056 operates over the full -40°C to +125°C
temperature range and runs from a supply voltage of
+2.7V to +5.5V. It is offered in a 2.02mm x 1.4mm 8-pin
wafer-level package (WLP) and 8-pin μMAX packages.
Applications
● PWM H-Bridge Motor In-line/In-phase/Winding
Current Sensing
● Solenoid Current Sensing
● Current Monitoring of Inductive Loads
● Battery Stack Monitors
● Automotive
19-100394; Rev 8; 2/21
Ordering Information appears at end of data sheet.
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
Typical Operating Characteristic
and Simplified Block Diagram
COMMON MODE REJ ECTION TO STEP INPUT
(STEP INPUT RISE/ FA L L TIMES AT 500V/μ s )toc17
VRS+=VRSVSTEP
AT
10V/div
RS+,RSINPUT
100mV/div
AC
COUPLED
VOUT
CLOAD= 0= 0
CLOAD
1μs/div
VDD
RY
RS+
RF
RX
RSPWM
REJECT
OUT
RP
RX
MAX40056
RP
RY
RF
REF
INTERNAL
1.5V
REFERENCE
COP
R
R
CIP
GND
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Maxim Integrated | 2
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
TABLE OF CONTENTS
General Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Benefits and Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Typical Operating Characteristic and Simplified Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Absolute Maximum Ratings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Package Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
8 µMAX. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
8 WLP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Typical Operating Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Pin Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Detailed Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
PWM Rejection Input Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Low Input Offset Voltage and Low Gain Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
CSA Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Voltage Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Window Comparator and Hysteresis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Applications Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Input Sense Voltage Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Choice of Reference Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Important Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Kelvin Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Stray Inductance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Current Sensing in a 3-Phase Servo Motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
www.maximintegrated.com
Maxim Integrated | 3
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
LIST OF FIGURES
Figure 1. Internal ESD Clamping Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Figure 2. Internal Window Comparator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Figure 3. Window Comparator Hysteresis Waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Figure 4. Kelvin Sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Figure 5. In-Line Current Sensing in Motor Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Figure 6. Current Sensing in a 3-Phase Servo Motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
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Maxim Integrated | 4
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
LIST OF TABLES
Table 1. Examples of VDD, VREF, and Sense Voltage Ranges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
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Maxim Integrated | 5
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
Absolute Maximum Ratings
RS+ and RS- to GND ................................................ -5V to +70V
RS+ to RS- ............................................................................. ±2V
VDD to GND.............................................................. -0.3V to +6V
REF, CIP, OUT, COP To GND..................... -0.3V to VDD + 0.3V
Continuous Current in REF, CIP ........................................... 5mA
Continuous Current in OUT and COP ................................. 10mA
Continuous Current in RS+ and RS-....................................10mA
Continuous Power Dissipation (Multi Layer Board) (TA = +70°C,
derate 4.8mW/°C above +70°C) .......................................390mW
Operating Temperature Range ...........................-40°C to +125°C
Storage Temperature Range ..............................-65°C to +150°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 Information
8 µMAX
Package Code
U8+4
Outline Number
21-0036
Land Pattern Number
90-0092
Thermal Resistance, Four-Layer Board:
Junction-to-Ambient (θJA)
206°C/W
Junction-to-Case Thermal Resistance (θJC)
42°C/W
8 WLP
Package Code
W81B2+1
Outline Number
21-100255
Land Pattern Number
Refer to Application Note 1891
Thermal Resistance, Four-Layer Board:
Junction-to-Ambient (θJA)
74.65°C/W
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages.
Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different
suffix character, but the drawing pertains to the package regardless of RoHS status.
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.maximintegrated.com/
thermal-tutorial.
Electrical Characteristics
(VDD = 3.3V, VCM = 48V, VSENSE = 20mV, OUT loading = 10kΩ and 20pF to GND, COP loading = 5kΩ and 10pF to GND, TMIN =
-40°C, TMAX = 125°C, (Note 1))
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
5.5
V
9
mA
POWER SUPPLY CHARACTERISTICS
Supply Voltage
VDD
Supply Current
IDD
Power-Up Time
tPWR_UP
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Guaranteed by PSRR
2.7
6
Out settle within 1%
400
µs
Maxim Integrated | 6
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
Electrical Characteristics (continued)
(VDD = 3.3V, VCM = 48V, VSENSE = 20mV, OUT loading = 10kΩ and 20pF to GND, COP loading = 5kΩ and 10pF to GND, TMIN =
-40°C, TMAX = 125°C, (Note 1))
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
-5
+70
V
-40°C ≤ TA ≤ +85°C
-0.3
+65
-40°C ≤ TA ≤ +125°C
-0.1
+65
CURRENT SENSE AMPLIFIER / DC CHARACTERISTICS
Input Protected CM
Range
Input Common Mode
Range
Input Bias Current
Input Leakage Current
Input Offset Voltage
VCM_P
VCM
IRS+ , IRSILKG
VOS
Input Offset Drift
TCVOS
Power Supply Rejection
Ratio
PSRR
Common Mode
Rejection Ratio
CMRR
Input Capacitance
Nominal Gain
Gain Error
VSENSE = 0V (Note 2)
3
200
nA
VSENSE = 20mV
20
30
µA
VDD = 0V, 0V ≤ VRS± ≤ 65V (Note 2)
3
200
nA
TA = +25°C
5
20
-40°C ≤ TA ≤ +125°C
300
μV
0.5
µV/°C
dB
2.7V ≤ VDD ≤ 5.5V
90
110
-0.3V ≤ VCM ≤ +65V; -40°C ≤ TA ≤ +85°C
100
140
-0.1V ≤ VCM ≤ +65V; -40°C ≤ TA ≤
+125°C
120
140
CIN
RS+ and RS- input
3
GU
MAX40056U
10
GT
MAX40056T
20
GF
MAX40056F
50
GE
V
pF
V/V
VCM = -0.3V, -40°C ≤ TA ≤ +85°C, -16mV
≤ VSENSE ≤ +16mV
0.05
1.5
VCM = 48V, -40°C ≤ TA ≤ +125°C, -16mV
≤ VSENSE ≤ +16mV
0.05
0.5
%
Output Voltage Swing
High
VOH
Sourcing 5mA; VOH = VDD - VOUT
45
100
mV
Output Voltage Swing
Low
VOL
Sinking 5mA; VOL = VOUT - GND
35
70
mV
Output Short-Circuit
Current
ISC
Shorted to either VDD or GND
20
mA
50% of full-scale range
300
kHz
1.5
V/µs
CURRENT SENSE AMPLIFIER / AC CHARACTERISTICS
Signal Bandwidth
BW-3dB
Output Slew Rate
SR
2VPP output square wave, centered at
1.5V
Amplifier Small-Signal
Settling Time (1%)
tS
±200mV output step
2.5
µs
PWM Edge Recovery
Settling Time
tS_PWM
0V to 50V edges: 500V/μs rise/fall times,
VSENSE = 0mV (VRS+ = VRS-)
500
ns
100mVAC Sine, f = 100kHz
70
dB
AC Common Mode
Rejection Ratio
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AC CMRR
Maxim Integrated | 7
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
Electrical Characteristics (continued)
(VDD = 3.3V, VCM = 48V, VSENSE = 20mV, OUT loading = 10kΩ and 20pF to GND, COP loading = 5kΩ and 10pF to GND, TMIN =
-40°C, TMAX = 125°C, (Note 1))
PARAMETER
SYMBOL
AC Power Supply
Rejection Ratio
AC PSRR
Voltage Noise Density
en
CONDITIONS
MIN
TYP
MAX
UNITS
100mVAC Sine, f = 100kHz
53
dB
At 10kHz
150
nV/√Hz
INTERNAL REFERENCE
REF Output Voltage
VREF
REF Thermal Drift
No load; -40°C ≤ TA ≤ +125°C
1.485
TCVREF
1.5
1.515
30
V
ppm/°C
REF Load Regulation
ΔVREF/ΔIREF
0µA ≤ external load ≤ 500µA
30
70
µV/µA
REF Line Regulation
ΔVREF/ΔVDD
2.7V ≤ VDD ≤ 5.5V
0.1
0.5
mV/V
REF Cap Loading
Internal\External
Reference Switching
Threshold Voltage
No sustained oscillation
VREF_TH
1
External reference is enabled by
overdriving
1.65
µF
1.75
V
INTERNAL COMPARATOR
CIP Input Resistance
RCIP
CIP Input Common
Mode Range
VCIP_IN
Input Offset Voltage
VOS_CMP
Hysteresis
VHYS
Resistance appears to be to VREF
10
MIN
(VREF 0.08,
VDD 1.25)
0.08
80mV ≤ VCIP ≤ min
(VREF - 80mV, VDD - 1.25V)
80mV ≤ VCIP ≤ min
(VREF - 80mV, VDD - 1.25V)
GΩ
V
10
mV
40
mV
COP Output Voltage
Swing High
VOH_CMP
Sourcing 2mA; VOH_CMP = VDD - VCOP
0.12
0.3
V
COP Output Voltage
Swing Low
VOL-CMP
Sinking 4mA; VOL_CMP = VCOP - GND
0.12
0.3
V
Propagation Delay
tPDL->H
200mV overdrive, low-to-high
14
tPDH->L
200mV overdrive, high-to-low
12
µs
Note 1: Limits are 100% tested at TA = +25°C. Limits over the operating temperature range and relevant supply voltage range are
guaranteed by design and characterization.
Note 2: Guaranteed by design and bench characterization.
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Maxim Integrated | 8
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
Typical Operating Characteristics
(VDD = 3.3V, VSENSE = 20mV, VCM = 48V, OUT LOAD = 10kΩ and 20pF to GND, COP LOAD = 5kΩ and 10pF to GND, TA = +25°C,
unless otherwise noted.)
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Maxim Integrated | 9
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
Typical Operating Characteristics (continued)
(VDD = 3.3V, VSENSE = 20mV, VCM = 48V, OUT LOAD = 10kΩ and 20pF to GND, COP LOAD = 5kΩ and 10pF to GND, TA = +25°C,
unless otherwise noted.)
www.maximintegrated.com
Maxim Integrated | 10
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
Typical Operating Characteristics (continued)
(VDD = 3.3V, VSENSE = 20mV, VCM = 48V, OUT LOAD = 10kΩ and 20pF to GND, COP LOAD = 5kΩ and 10pF to GND, TA = +25°C,
unless otherwise noted.)
www.maximintegrated.com
Maxim Integrated | 11
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
Typical Operating Characteristics (continued)
(VDD = 3.3V, VSENSE = 20mV, VCM = 48V, OUT LOAD = 10kΩ and 20pF to GND, COP LOAD = 5kΩ and 10pF to GND, TA = +25°C,
unless otherwise noted.)
www.maximintegrated.com
Maxim Integrated | 12
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
Typical Operating Characteristics (continued)
(VDD = 3.3V, VSENSE = 20mV, VCM = 48V, OUT LOAD = 10kΩ and 20pF to GND, COP LOAD = 5kΩ and 10pF to GND, TA = +25°C,
unless otherwise noted.)
www.maximintegrated.com
Maxim Integrated | 13
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
Typical Operating Characteristics (continued)
(VDD = 3.3V, VSENSE = 20mV, VCM = 48V, OUT LOAD = 10kΩ and 20pF to GND, COP LOAD = 5kΩ and 10pF to GND, TA = +25°C,
unless otherwise noted.)
Pin Configuration
TOP VIEW
1
COP
+
8
RS-
2
7
CIP
VDD
3
6
GND
OUT
4
5
REF
µMAX
www.maximintegrated.com
2
3
4
A
RS+
COP
VDD
OUT
B
RS-
CIP
GND
REF
+
RS+
1
WLP
Maxim Integrated | 14
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
Pin Description
PIN
NAME
FUNCTION
1
RS+
External Resistor Power-Side Connection Input
2
COP
Active-Low Comparator Push-Pull Output. Output low indicates fault condition.
3
VDD
Supply Voltage Input. +2.7V to +5.5V. Bypass to ground with a 10nF COG\NPO and 1µF X5R.
4
OUT
Current-Sense Output. Output has its common mode point at VREF.
8
RS-
External Resistor Load-Side Connection Input
7
CIP
Comparator Input/Overcurrent Threshold Input
6
GND
Ground. Signal and power return.
Internal 1.5V Reference Output. Intended to be used with OUT to indicate the current's direction.
Bypass to GND with a 10nF and a 1µF capacitors.
5
REF
Connect external reference greater than 1.5V to override internal reference and change output
common mode voltage.
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Maxim Integrated | 15
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
Detailed Description
VDD
MAX40056
RS-
VDD
OUT
RS+
GND
GND
VDD
REF
GND
VDD
INTERNAL/
EXTERNAL
REF
SELECT
VDD
COP
R
CIP
R
GND
GND
GND
Figure 1. Internal ESD Clamping Structure
Overview
The MAX40056 is a single-supply, high-accuracy, bidirectional current sense amplifier with a high common-mode input
range extending from -0.1V to +65V. The input stage provides protection against voltage spikes and inductive kickbacks
from -5V up to +70V. The ±5μV (typ) input offset voltage and 0.05% (typ) gain error help to ensure low system errors.
The input stage is specifically designed to suppress the disturbance of fast PWM signals, which are common in motor
control applications. The MAX40056 is, therefore, well-suited for in-phase current monitoring of inductive loads, such as
motor windings and solenoids that are driven by PWM signals. The MAX40056 operates over the full -40°C to +125°C
temperature range and from a supply voltage of +2.7V to +5.5V.
Figure 1 shows the internal clamping/protection structure.
PWM Rejection Input Stage
The proprietary input architecture is immune to the large PWM disturbances present in a typical motor control application.
The input stage is designed to withstand -5V to +70V common-mode input voltage without damage. The MAX40056
output recovers within 500ns from PWM edges with slew rates up to and beyond ±500V/µs.
Low Input Offset Voltage and Low Gain Error
The MAX40056 utilizes chopper-stabilized architecture to achieve a low input offset voltage less than ±20µV. This
technique also enables extremely low input offset voltage drift over time and temperature to 500nV/°C. The precision
input VOS specification allows accurate current measurements with low value current-sense resistors, thus reducing
voltage drop and power dissipation on sense resistors. The optimized gain architecture achieves a gain error of less than
0.5% over the entire temperature range of -40°C to +125°C.
CSA Output
From the functional block diagram shown, the MAX40056 CSA output is given by the following equation
{
}
VOUT= {ISENSE × RSENSE} × GAIN +VREF...(1)
Where, ISENSE is the current to be measured, RSENSE is the sense resistor value, GAIN is the voltage gain of the CSA.
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Maxim Integrated | 16
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
The gain is 50V/V for the MAX40056F, 20V/V for the MAX40056T, and 10V/V for the MAX40056U respectively. VREF
is the reference voltage. This is either the internal integrated reference voltage (1.5V) or an external voltage reference
connected to the REF input. When the sense current is positive (the current flows from the RS+ input to the RS- input
through the sense resistor), the output voltage is greater than VREF (V), when the sense current is negative, the output
voltage is less than VREF (V) indicating negative currents flowing with respect to RS+ and RS- inputs.
Voltage Reference
The voltage reference offsets the amplifier output to VREF when the sensed current is 0A. From Equation (1), the direction
of the sensed current can be easily determined by comparing VOUT with VREF.
The MAX40056 has an internal 1.5V voltage reference for use with a nominal 3.3V supply. The internal VREF output can
source a small amount current for external loads. The load regulation of the internal reference is 30μV/μA, so care must
be taken to ensure that the accuracy of the reference is maintained when the reference is sourcing current.
When operating from higher supply voltages, a higher full-scale output swing is often desired. In this case, the internal
reference can be overridden by a higher-voltage external reference. The integrated comparator constantly compares
the internal reference voltage and the voltage on the REF input/output so that the higher reference voltage is always
selected.
Window Comparator and Hysteresis
The MAX40056 features an integrated internal window comparator to detect both positive and negative over current
conditions. The window comparator (shown in Figure 2) compares the current sense amplifier output VOUT with a low
threshold (VCIP) and a high threshold (VA). VCIP is generated by an external resistor divider connected to the REF
output, and the VCIP input range should be within 80mV to MIN ((VREF - 80mV), (VDD - 1.25V)) for proper operation.
VA is internally generated from VREF and VCIP : VA = (2 × VREF) − VCIP, with a range from (VREF + 80mV) to (2xVREF
– 80mV). Either the internal or an external reference can be used to define the thresholds for the integrated window
comparators.
VOUT
VREF
R
CIP
COMP_HI
VA
COP
R
COMP_LO
Figure 2. Internal Window Comparator
When VOUT is greater than VA or when VOUT is less than VCIP , the comparator output is low, indicating a fault condition.
The hysteresis direction is shown in Figure 3. COMP_HI and COMP_LO have the same hysteresis direction. When V+
rises across V-, both comparators have no hysteresis voltage; when V+ falls across V-, both comparators have a similar
hysteresis voltage, thereby providing equivalent noise immunity.
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Maxim Integrated | 17
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
VA = (2xVREF) - VCIP
VREF - VCIP
VREF
VREF - VCIP
VCIP = 50mV TO (VREF – 50mV)
VOUT = 0mV TO VDD
VCOP
Hysteresis in rising
lower threshold
Hysteresis in falling
upper threshold
Figure 3. Window Comparator Hysteresis Waveform
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Maxim Integrated | 18
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
Applications Information
Input Sense Voltage Range
The maximum input differential voltage range is given by the following relation:
VSENSE =
{
{GND − VREF} TO {VDD − VREF}
GAIN
GAIN
}
If VDD = +3.3V and the MAX40056T (Gain = 20V/V) is used with the 1.5V internal reference, the above equation would
provide:
VSENSE =
{{
}
0V − 1.5V} {3.3V − 1.5V}
,
= − 75mVTO + 90mV
20V / V
20V / V
For further information on input differential voltage range for different VDD and choice of reference, please refer to Table
1. Refer to the Electrical Characteristics for the Gain Error specifications. The typical gain error performance for input
differential sense range beyond the specified conditions, as shown below.
Choice of Reference Voltage
As the input full scale range is proportional to the VREF and VDD, the input differential sense range can be extended
by using an external voltage reference and a higher supply voltage. To achieve the maximum possible input and output
range, it is recommended to choose a reference votlage that is half of the supply voltage (VDD). As an example,
when VDD = 5.0V, select VREF = 2.5V. Note that the internal reference may be used with higher supply voltage. The
low-side output swing will be the same as for low supply voltages, and the high side swing it is recommended to have the
reference voltage to the MAX40056 to be half of the supply voltage. For example, when VDD = 5.0V, select VREF = 2.5V.
Table 1 lists the examples of VDD, VREF, GAIN, and sense voltage combinations.
Table 1. Examples of VDD, VREF, and Sense Voltage Ranges
DEVICE
GAIN
(V/V)
MAX40056F
50
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SUPPLY
VOLTAGE (V)
INTERNAL
REFERENCE (V)
EXTERNAL
REFERENCE (V)
INPUT DIFFERENTIAL SENSE RANGE
VSENSE_FS (mV)
3.3
1.5
–
-30 to +36
5.0
–
2.5
-50 to +50
Maxim Integrated | 19
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
Table 1. Examples of VDD, VREF, and Sense Voltage Ranges (continued)
DEVICE
GAIN
(V/V)
MAX40056T
20
MAX40056U
10
SUPPLY
VOLTAGE (V)
INTERNAL
REFERENCE (V)
EXTERNAL
REFERENCE (V)
INPUT DIFFERENTIAL SENSE RANGE
VSENSE_FS (mV)
3.3
1.5
–
-75 to +90
5.0
–
2.5
-125 to +125
3.3
1.5
–
-150 to +180
5.0
–
2.5
-250 to +250
The internal 1.5V integrated reference can be used as a reference for higher supply voltages (VDD). The range of input
range is extended only on the positive direction.
Important Considerations
Kelvin Connections
Due to the high currents that may flow through RSENSE, take care to eliminate solder and parasitic trace resistance from
causing errors in the sense voltage. Either use a four-terminal current sense resistor or use Kelvin (force and sense) PCB
layout techniques.
Figure 4 shows a typical routing of Kelvin-sensed traces to the inputs of the MAX40056. The Kelvin-sense traces should
be as close as possible to the current-sense resistor's solder contact pads. If the Kelvin-sensing contact pads are spaced
wider relative to the sense resistor, error is introduced from the additional trace resistance.
VDD
PCB Trace
RSENSE
ILOAD
RSOUT
RS+
MAX40056
Figure 4. Kelvin Sensing
Stray Inductance
The stray inductance due to package parasitics in the current sense resistor should be kept minimum. The unwanted
voltage error produced of the stray inductance is proportional to the magnitude of the load current. Wire-wound resistors
have the highest inductance, while metal film is comparably better.
Low-inductance, metal-film resistors are also available. Instead of being spiral wrapped around a core, as in metal-film
or wire wound resistors, they are straight bands of metal and are available in values under 100mΩ.
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Maxim Integrated | 20
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
VPOWER = 9V TO 48V
RSENSE_POWER
Φ2
RS+
Φ3
RS-
VDD
MAX40056
REF
GND
OUT
CIP COP
TO µC
R1
RSENSEΦ1
R2
RSENSEΦ2
RSENSEΦ3
RS+
RS-
VDD
MAX40056
REF
GND
Φ2
OUT
CIP COP
TO µC
R1
Φ3
R2
VDD
RSENSE_PGND
RS+
RSGND
MAX40056
REF
OUT
CIP COP
TO µC
R1
R2
Figure 5. In-Line Current Sensing in Motor Control
Figure 5 shows a typical 3-Phase motor control application. The MAX40056s are connected across the RSENSE resistors
to determine the instantaneous in-line phase currents going into the motor.
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Maxim Integrated | 21
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
VPOWER = 9V TO 48V
RSENSE_POWER
Φ1
Φ2
Φ3
VDD
R
MAX40056
RSENSEΦ1
OUT(Φ1)
REF
VDD
R
VDD
R
OUT(Φ2)
RSENSEΦ2
OUT(Φ3)
MAX44290
REF
MAX40056
200kΩ
100kΩ
Φ1
Φ2
Φ3
RSENSE_PGND
R = 5kΩ
OUT(Φ3)(V) = VREF(V) – (OUT(Φ1) +OUT(Φ2))(V)
Figure 6. Current Sensing in a 3-Phase Servo Motor
Current Sensing in a 3-Phase Servo Motor
The outputs of two current sense amplifiers can be summed, as shown in Figure 6, to generate a voltage representing
the third winding's current.
By Kirchhoff’s Law, the third winding current equals the sum of the other two windings, so a simple op-amp summing
circuit with three equal-valued resistors is sufficient to produce a voltage proportional to third winding current. Select a
large enough resistor value to avoid excessively loading the op-Amp or the CSA outputs. All three amplifiers share the
system reference voltage, allowing ratio-metric measurements. If the three amplifiers drive ADC inputs, they will typically
share the ADC’s supply voltage.
This circuit provides instantaneous winding currents of all three phases without any further computation or knowledge of
the PWM pulse phases or duty cycles. Note that the supply bypass capacitors, transient suppressors and catch diodes
were omitted for clarity.
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Maxim Integrated | 22
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
Ordering Information
PART NUMBER
TEMP RANGE
PIN-PACKAGE
TOP MARK
GAIN
MAX40056FAUA+
-40°C to +125°C
8 μMAX
+FAUA
50V/V
MAX40056FAUA/V+
-40°C to +125°C
8 μMAX
+FA/V
50V/V
MAX40056FAWA+
-40°C to +125°C
8 WLP
—
50V/V
MAX40056TAUA+
-40°C to +125°C
8 μMAX
—
20V/V
MAX40056TAUA/V+*
-40°C to +125°C
8 μMAX
+TA/V
20V/V
MAX40056TAWA+*
-40°C to +125°C
8 WLP
+AAP
20V/V
MAX40056UAUA+
-40°C to +125°C
8 μMAX
—
10V/V
MAX40056UAUA/V+
-40°C to +125°C
8 μMAX
+UA/V
10V/V
MAX40056UAWA+
-40°C to +125°C
8 WLP
+AAQ
10V/V
+Denotes a lead(Pb)-free/RoHS-compliant package.
*Future product—contact factory for availability.
/V denotes an automotive qualified part.
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Maxim Integrated | 23
MAX40056F/MAX40056T/
MAX40056U
Bidirectional Current Sense
Amplifier with PWM-Rejection
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
0
8/18
Initial release
1
1/19
Updated Ordering Information and Applications
2
5/19
Updated Benefits and Features, Electrical Characteristics, and Detailed Description
3
6/19
Updated Ordering Information
4
8/19
Updated Input Common Mode specification in Electrical Characteristics table
3
5
11/19
Updated Ordering Information
20
6
1/20
Updated Ordering Information
20
7
1/21
Updated Benefits and Features and Ordering Information
8
2/21
Updated Ordering Information
DESCRIPTION
—
1, 21
1, 4, 12
20
1, 20
22
For pricing, delivery, and ordering information, please visit Maxim Integrated’s online storefront at https://www.maximintegrated.com/en/storefront/storefront.html.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent
licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max
limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
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