General Description
The MAX9634 high-side current-sense amplifier offers
precision accuracy specifications of V
OS
less than
250µV (max) and gain error less than 0.5% (max).
Quiescent supply current is an ultra-low 1µA. The
MAX9634 fits in a tiny, 1mm x 1mm UCSP™ package
size or a 5-pin SOT23 package, making the part ideal for
applications in notebook computers, cell phones, PDAs,
and all battery-operated portable devices where accuracy, low quiescent current, and small size are critical.
The MAX9634 features an input common-mode voltage
range from 1.6V to 28V. These current-sense amplifiers
have a voltage output and are offered in four gain versions:
25V/V (MAX9634T), 50V/V (MAX9634F), 100V/V
(MAX9634H), and 200V/V (MAX9634W).
The four gain selections offer flexibility in the choice of
the external current-sense resistor. The very low 250µV
(max) input offset voltage allows small 25mV to 50mV
full-scale V
SENSE
voltage for very low voltage drop at
full-current measurement.
The MAX9634 is offered in tiny 4-bump UCSP (1mm x
1mm x 0.6mm footprint) and 5-pin SOT23 packages
specified for operation over the -40°C to +85°C extended temperature range.
Applications
Cell Phones
PDAs
Power-Management Systems
Portable/Battery-Powered Systems
Notebook Computers
Features
o Ultra-Low Supply Current of 1µA (max)
o Low 250µV (max) Input Offset Voltage
o Low < 0.5% (max) Gain Error
o Input Common Mode: +1.6V to +28V
o Voltage Output
o Four Gain Versions Available
25V/V (MAX9634T)
50V/V (MAX9634F)
100V/V (MAX9634H)
200V/V (MAX9634W)
o Tiny 1mm x 1mm x 0.6mm, 4-Bump UCSP or
5-Pin SOT23 Packages
MAX9634
1µA, 4-Bump UCSP/SOT23,
Precision Current-Sense Amplifier
________________________________________________________________
Maxim Integrated Products
1
Pin Configurations
19-5021; Rev 1; 2/10
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.
EVALUATION KIT
AVAILABLE
UCSP is a trademark of Maxim Integrated Products, Inc.
Ordering Information
+
Denotes a lead(Pb)-free/RoHS-compliant package.
Note: All devices are specified over the -40°C to +85°C
extended temperature range.
PART
PIN-
GAIN
(V/V)
TOP
MARK
MAX9634TERS+ 4 UCSP 25 +ABX
MAX9634FERS+ 4 UCSP 50 +ABY
MAX9634HERS+ 4 UCSP 100 +ABZ
MAX9634WERS+ 4 UCSP 200 +ACA
MAX9634TEUK+ 5 SOT23 25
+AFHG
MAX9634FEUK+ 5 SOT23 50
+AFHH
MAX9634HEUK+ 5 SOT23 100 +AFHI
MAX9634WEUK+ 5 SOT23 200 +AFHJ
PACKAGE
TOP VIEW
(BUMPS ON BOTTOM)
A1
RS+
MAX9634T/F/H/W
B1 B2
GND
DRAWINGS NOT TO SCALE
UCSP
RS-A2
OUT
RS+ RS-
54
MAX9634T/F/H/W
132
GND OUTGND
SOT23
MAX9634
1µA, 4-Bump UCSP/SOT23,
Precision Current-Sense Amplifier
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V
RS+
= V
RS-
= 3.6V, V
SENSE
= (V
RS+
- V
RS-
) = 0V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
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.
RS+, RS- to GND....................................................-0.3V to +30V
OUT to GND .............................................................-0.3V to +6V
RS+ to RS- ...........................................................................±30V
Short-Circuit Duration: OUT to GND ..........................Continuous
Continuous Input Current (any pin) ..................................±20mA
Continuous Power Dissipation (T
A
= +70°C)
4-Bump UCSP (derate 3.0mW/°C above +70°C).........238mW
5-Pin SOT23 (derate 3.9mW/°C above +70°C)............312mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range ............................-65°C to +150°C
Bump Temperature (soldering) Reflow............................+260°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) .......................................+260°C
Supply Current (Note 2) I
Common-Mode Input Range V
Common-Mode Rejection Ratio CMRR 1.6V < V
Input Offset Voltage (Note 3) V
Gain G
Gain Error (Note 4) GE
Output Resistance (Note 5) R
OUT Low Voltage V
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
V
= 5V, TA = +25°C 0.5 0.85
RS+
V
= 5V, -40°C < TA < +85°C 1.1
CC
CM
OS
OUT
OL
RS+
V
= 28V, TA = +25°C 1.1 1.8
RS+
V
= 28V, -40°C < TA < +85°C 2.5
RS+
Guaranteed by CMRR, -40°C < TA < +85°C 1.6 28 V
RS+
MAX9634T/MAX9634F/
MAX9634H
MAX9634W
MAX9634T 25
MAX9634F 50
MAX9634H 100
MAX9634W 200
MAX9634T/MAX9634F/
MAX9634H
MAX9634W
MAX9634T/MAX9634F/MAX9634H 7.0 10 13.2
MAX9634W 14.0 20 26.4
Gain = 25 1.5 7.5
Gain = 50 3 15
Gain = 100 6 30
Gain = 200 12 85
< 28V, -40°C < TA < +85°C 94 130 dB
TA = +25°C 100 250
-40°C < T
TA = +25°C 100 250
-40°C < T
TA = +25°C ±0.1 ±0.5
-40°C < T
TA = +25°C ±0.1 ±0.7
-40°C < T
< +85°C 300
A
< +85°C 425
A
< +85°C ±0.6
A
< +85°C ±0.8
A
µA
µV
V/V
%
kΩ
mV
MAX9634
1µA, 4-Bump UCSP/SOT23,
Precision Current-Sense Amplifier
_______________________________________________________________________________________ 3
Note 1: All devices are 100% production tested at TA= +25°C. All temperature limits are guaranteed by design.
Note 2: V
OUT
= 0. ICCis the total current into RS+ plus RS- pins.
Note 3: V
OS
is extrapolated from measurements for the gain-error test.
Note 4: Gain error is calculated by applying two values of V
SENSE
and calculating the error of the slope vs. the ideal:
Gain = 25, V
SENSE
is 20mV and 120mV.
Gain = 50, V
SENSE
is 10mV and 60mV.
Gain = 100, V
SENSE
is 5mV and 30mV.
Gain = 200, V
SENSE
is 2.5mV and 15mV.
Note 5: The device is stable for any external capacitance value.
Note 6: V
OH
is the voltage from V
RS-
to V
OUT
with V
SENSE
= 3.6V/gain.
ELECTRICAL CHARACTERISTICS (continued)
(V
RS+
= V
RS-
= 3.6V, V
SENSE
= (V
RS+
- V
RS-
) = 0V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
Typical Operating Characteristics
(V
RS+
= V
RS-
= 3.6V, TA= +25°C, unless otherwise noted.)
0
10
5
20
15
25
30
-0.4 -0.3 -0.2 -0.1 0 0.2 0.30.1 0.4
INPUT OFFSET VOLTAGE HISTOGRAM
MAX9634 toc01
INPUT OFFSET VOLTAGE (mV)
N (%)
0
10
5
20
15
25
30
-0.4 -0.3 -0.2 -0.1 0 0.2 0.30.1 0.4
GAIN ERROR HISTOGRAM
MAX9634 toc02
GAIN ERROR (%)
N (%)
SUPPLY CURRENT
vs. TEMPERATURE
MAX9634 toc03
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
10-15 35 60
0.4
0.2
0.6
0.8
1.0
1.2
1.4
28V
3.6V
1.8V
0
-40 85
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
OUT High Voltage V
Small-Signal Bandwidth
(Note 5)
Output Settling Time t
Power-Up Time t
V
= V
- V
OH
BW
ON
V
V
V
V
1% final value, V
S
1% final value, V
OH
RS-
= 50mV, gain = 25 125
SENSE
= 50mV, gain = 50 60
SENSE
= 50mV, gain = 100 30
SENSE
= 50mV, gain = 200 15
SENSE
(Note 6) 0.1 0.2 V
OUT
= 50mV 100 µs
SENSE
= 50mV 200 µs
SENSE
kHz
MAX9634
1µA, 4-Bump UCSP/SOT23,
Precision Current-Sense Amplifier
4 _______________________________________________________________________________________
GAIN
ERROR
(%)
Typical Operating Characteristics (continued)
(V
RS+
= V
RS-
= 3.6V, TA= +25°C, unless otherwise noted.)
INPUT OFFSET
vs. COMMON-MODE VOLTAGE
-30
-35
-40
-45
INPUT OFFSET (µV)
-50
-55
030
COMMON-MODE VOLTAGE (V)
GAIN ERROR
vs. COMMON-MODE VOLTAGE
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5
010155 202530
VOLTAGE (V)
INPUT OFFSET
vs. TEMPERATURE
MAX9634 toc05
1.4
1.2
1.0
0.8
0.6
SUPPLY CURRENT (µA)
0.4
0.2
0
0
60
MAX9634 toc04
252010515
50
40
30
INPUT OFFSET (µV)
20
10
0
10-15 35 60-40 85
TEMPERATURE (°C)
GAIN ERROR
vs. TEMPERATURE
MAX9634 toc07
0.08
0.07
0.06
0.05
0.04
0.03
GAIN ERROR (%)
0.02
0.01
0
-40
10 60 8535-15
TEMPERATURE (°C)
MAX9634 toc08
4.0
3.5
3.0
2.5
(V)
2.0
OUT
V
1.5
1.0
0.5
0
0150
SUPPLY CURRENT
vs. COMMON-MODE VOLTAGE
15 2010 30525
COMMON-MODE VOLTAGE (V)
V
vs. V
OUT
SENSE
(SUPPLY = 3.6V)
G = 100
G = 50
G = 25
10050
V
(mV)
SENSE
MAX9634 toc06
MAX9634 toc09
V
vs. V
OUT
SENSE
(SUPPLY = 1.6V)
1.8
1.6
1.4
1.2
V
G = 50
SENSE
G = 100
G = 25
80604020
(mV)
1.0
(V)
OUT
V
0.8
0.6
0.4
0.2
0
0100
MAX9634 toc10
5
0
-5
-10
GAIN (dB)
-15
-20
-25
-30
1
SMALL-SIGNAL GAIN
vs. FREQUENCY
AV = 25V/V
AV = 100V/V
AV = 50V/V
FREQUENCY (Hz)
0
vs. FREQUENCY
-20
MAX9634 toc11
-40
-60
-80
GAIN (dB)
-100
-120
-140
100k10 1M100 10k1k
-160
G = 25
1
CMRR
MAX9634 toc12
G = 50
G = 100
100k10 1M100 10k1k
FREQUENCY (Hz)
MAX9634
1µA, 4-Bump UCSP/SOT23,
Precision Current-Sense Amplifier
_______________________________________________________________________________________ 5
Typical Operating Characteristics (continued)
(V
RS+
= V
RS-
= 3.6V, TA= +25°C, unless otherwise noted.)
Pin Description
V
V
SMALL-SIGNAL PULSE RESPONSE
(GAIN = 100)
SENSE
V
OUT
20µs/div
LARGE-SIGNAL PULSE RESPONSE
(GAIN = 100)
SENSE
V
OUT
MAX9634 toc13a
MAX9634 toc14a
15mV
10mV
1.5V
1V
30mV
10mV
3V
1V
V
V
SMALL-SIGNAL PULSE RESPONSE
(GAIN = 50)
SENSE
V
OUT
25µs/div
LARGE-SIGNAL PULSE RESPONSE
(GAIN = 50)
SENSE
V
OUT
MAX9634 toc13b
MAX9634 toc14b
30mV
20mV
1.5V
1V
60mV
10mV
3V
0.5V
V
V
SMALL-SIGNAL PULSE RESPONSE
(GAIN = 25)
SENSE
V
OUT
25µs/div
LARGE-SIGNAL PULSE RESPONSE
(GAIN = 25)
SENSE
V
OUT
MAX9634 toc13c
MAX9634 toc14c
60mV
40mV
1.5V
1V
120mV
20mV
3V
0.5V
20µs/div
25µs/div
PIN
UCSP SOT23
A1 5 RS+ External Sense Resistor Power-Side Connection
A2 4 RS- External Sense Resistor Load-Side Connection
B1 1, 2 GND Ground
B2 3 OUT Output Voltage. V
NAME FUNCTION
is proportional to V
OUT
SENSE
25µs/div
= V
RS+
- V
RS-
.
MAX9634
1µA, 4-Bump UCSP/SOT23,
Precision Current-Sense Amplifier
6 _______________________________________________________________________________________
Detailed Description
The MAX9634 unidirectional high-side, current-sense
amplifier features a 1.6V to 28V input common-mode
range. This feature allows the monitoring of current out
of a battery with a voltage as low as 1.6V. The
MAX9634 monitors current through a current-sense
resistor and amplifies the voltage across that resistor.
The MAX9634 is a unidirectional current-sense amplifier
that has a well-established history. An op amp is used
to force the current through an internal gain resistor at
RS+, which has a value of R1, such that its voltage drop
equals the voltage drop across an external sense resistor, R
SENSE
. There is an internal resistor at RS- with the
same value as R
1
to minimize offset voltage. The current through R1is sourced by a high-voltage p-channel
FET. Its source current is the same as its drain current,
which flows through a second gain resistor, R
OUT
. This
produces an output voltage, V
OUT
, whose magnitude is
I
LOAD
x R
SENSE
x R
OUT/R1
. The gain accuracy is
based on the matching of the two gain resistors R1and
R
OUT
(see Table 1). Total gain = 25V/V for the
MAX9634T, 50V/V for the MAX9634F, 100V/V for the
MAX9634H, and 200V/V for the MAX9634W. The output
is protected from input overdrive by use of an output
current-limiting circuit of 7mA (typical) and a 6V clamp
protection circuit.
Applications Information
Choosing the Sense Resistor
Choose R
SENSE
based on the following criteria:
Voltage Loss
A high R
SENSE
value causes the power-source voltage
to drop due to IR loss. For minimal voltage loss, use the
lowest R
SENSE
value.
Table 1. Internal Gain-Setting Resistors
(Typical Values)
Typical Operating Circuit
I
V
= 1.6V TO 28V
BATT
LOAD
R
SENSE
RS+ RS-
R
R
OUT
1
P
10kΩ
GND
GAIN
(V/V)
200 100 20
100 100 10
50 200 10
25 400 10
R
(Ω)
1
R
(kΩ)
OUT
R
1
MAX9634
OUT
VDD = 3.3V
µC
ADC
LOAD
MAX9634
1µA, 4-Bump UCSP/SOT23,
Precision Current-Sense Amplifier
_______________________________________________________________________________________ 7
OUT Swing vs. V
RS+
and V
SENSE
The MAX9634 is unique because the supply voltage is
the input common-mode voltage (the average voltage
at RS+ and RS-). There is no separate VCCsupply voltage pin. Therefore, the OUT voltage swing is limited by
the minimum voltage at RS+.
V
OUT
(max) = V
RS+
(min) - V
SENSE
(max) - V
OH
and:
V
SENSE
full scale should be less than V
OUT
/GAIN at the
minimum RS+ voltage. For best performance with a
3.6V supply voltage, select R
SENSE
to provide approximately 120mV (gain of 25V/V), 60mV (gain of 50V/V),
30mV (gain of 100V/V), or 15mV (gain of 200V/V) of
sense voltage for the full-scale current in each application. These can be increased by use of a higher minimum input voltage.
Accuracy
In the linear region (V
OUT
< V
OUT
(max)), there are two
components to accuracy: input offset voltage (VOS) and
gain error (GE). For the MAX9634, VOS= 250µV (max)
and gain error is 0.5% (max). Use the linear equation:
V
OUT
= (gain ± GE) x V
SENSE
± (gain x VOS)
to calculate total error. A high R
SENSE
value allows lower
currents to be measured more accurately because offsets are less significant when the sense voltage is larger.
Efficiency and Power Dissipation
At high current levels, the I2R losses in R
SENSE
can be
significant. Take this into consideration when choosing
the resistor value and its power dissipation (wattage)
rating. Also, the sense resistor’s value might drift if it is
allowed to heat up excessively. The precision V
OS
of
the MAX9634 allows the use of small sense resistors to
reduce power dissipation and reduce hot spots.
Kelvin Connections
Because of the high currents that flow through R
SENSE
,
take care to eliminate parasitic trace resistance from
causing errors in the sense voltage. Either use a fourterminal current-sense resistor or use Kelvin (force and
sense) PCB layout techniques.
Optional Output Filter Capacitor
When designing a system that uses a sample-and-hold
stage in the ADC, the sampling capacitor momentarily
loads OUT and causes a drop in the output voltage. If
sampling time is very short (less than a microsecond),
consider using a ceramic capacitor across OUT and
GND to hold V
OUT
constant during sampling. This also
decreases the small-signal bandwidth of the currentsense amplifier and reduces noise at OUT.
R
SENSE
V
OUT
=
GI
×
LOAD
(max)
(max)
MAX9634
1µA, 4-Bump UCSP/SOT23,
Precision Current-Sense Amplifier
8 _______________________________________________________________________________________
Bidirectional Application
Battery-powered systems may require a precise bidirectional current-sense amplifier to accurately monitor
the battery’s charge and discharge currents.
Measurements of the two separate outputs with respect
to GND yields an accurate measure of the charge and
discharge currents, respectively (Figure 1).
UCSP Applications Information
For the latest application details on UCSP construction,
dimensions, tape carrier information, PCB techniques,
bump-pad layout, and recommended reflow temperature profile, as well as the latest information on reliability
testing results, refer to Application Note 1891:
Wafer-
Level Packaging (WLP) and Its Applications
.
.
Chip Information
PROCESS: BiCMOS
Figure 1. Bidirectional Application
I
V
= 1.6V TO 28V
BATT
LOAD
R
SENSE
RS+ RS-RS- RS+
R
1
R
1
R
1
R
1
LOAD
TO WALL-CUBE/
CHARGER
P
R
OUT
MAX9634
GND
OUT OUT
P
MAX9634
R
10kΩ10kΩ
OUT
GND
VDD = 3.3V
µC
ADC
ADC
MAX9634
1µA, 4-Bump UCSP/SOT23,
Precision Current-Sense Amplifier
_______________________________________________________________________________________ 9
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.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 TYPE PACKAGE CODE DOCUMENT NO.
2 x 2 UCSP R41A1+1
21-0242
5 SOT23 U5-2
21-0057
2x2 UCSP.EPS
MAX9634
1µA, 4-Bump UCSP/SOT23,
Precision Current-Sense Amplifier
10 ______________________________________________________________________________________
Package Information (continued)
For the latest package outline information and land patterns, go to www.maxim-ic.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.
SOT-23 5L .EPS
MAX9634
1µA, 4-Bump UCSP/SOT23,
Precision Current-Sense Amplifier
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 ____________________
11
© 2010 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
Revision History
REVISION
NUMBER
0 10/09 Initial release —
1 2/10 Corrected gain error limits in Electrical Characteristics table 2
REVISION
DATE
DESCRIPTION
PAGES
CHANGED
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