SEMTECH SC310

SC310
High-Side Current-Sense Amplifier
with Low Impedance Voltage Output
POWER MANAGEMENT
Description
Features
The SC310 is a high-side current sense amplifier ideal for
any application where precision current monitoring is
needed. Possible uses include battery-powered products
such as cellphones and notebooks, as well as industrial
and data acquisition applications. The wide 2.7V to 25V
common mode input range is independent of supply range,
providing complete flexibility in battery sensing applications.
Three gain versions (20V/V, 50V/V, 100V/V)
available
2.7V to 25V input common mode range
3V to 25V supply voltage range
270 μA supply current
1% typical accuracy
Buffered low impedance voltage output
Industrial temperature range (-40°C to +125°C)
Small, lead-free SOT23-6 Package
The Current-Sense Amplifier offers three gain versions,
SC310A (gain 20 V/V), SC310B (gain 50 V/V) and
SC310C (gain 100 V/V). An external shutdown pin
(SHDN) enables turn off for the IC. A buffered output
with low impedance renders the overall gain immune to
load resistance. Output range is from 0V to Vcc - 1.7V.
Applications
Notebook and Tablet PCs
Data Acquisition
Battery Packs
Charging Applications
Industrial and Embedded Applications
Other features include tiny SOT-23-6 packaging, very low
supply current, and wide supply voltage range (3V to 25V).
The SC310 is rated for operation over the Industrial Temperature range (-40°C to +125°C).
Typical Application Circuit
R SENSE
ILOAD
CS+
CS-
VCC
OUT
SHDN
GND
2.7V to 25V
3V - 25V
0.1uF
June 4, 2007
V OUT
Load/
Battery
0.1uF
www.semtech.com
1
SC310
POWER MANAGEMENT
Absolute Maximum Ratings
Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters
specified in the Electrical Characteristics section is not implied.
Parameter
Symbol
Min
Max
Units
VCC
-0.3
28
V
VCS+ - VCS-
0.5
V
Thermal Resistance Junction
θJA
230
°C/W
Thermal Resistance Junction to Case
θJC
81
°C/W
Operating Temperature Range
TA
-40
+125
°C
Storage Temperature Range
TSTG
-65
+150
°C
Junction Temperature Range
TJ
-65
+150
°C
260
°C
Supply Voltage
Differential Input Voltage
Lead Temperature (Soldering) 10s
TLEAD
CS+ Voltage
VCS+
-0.3
VCC + 0.3
V
CS- Voltage
VCS-
-0.3
VCC + 0.3
V
SHDN Voltage
VSHDN
-0.3
VCC + 0.3
V
ESD Rating (Human Body Model)
VESD
2
kV
Electrical Characteristics
VCS+ = 2.7V to 25V, VCC = 3V to 25V, VSENSE = 0, TA = TJ = -40°C to +125°C , unless otherwise specified
P a r a met er
Symb ol
Operating Voltage Range
VCC
Common-Mode Input Range
VCMR
Common-Mode Rejection
C on d i t i on s
Mi n
Ma x
Un i ts
3
25
V
0°C ≤ TA ≤ +125°C
2.7
25
V
-40°C ≤ TA < 0°C
3
25
CMR
Ty p
90
Supply Current
ICC
VCS+ > 2.7V, VCC = 12V
0.27
Input Bias Current
ICS+
VCS+ > +2.7V
150
ICS-
VCS+ > +2.7V
VSENSE
VSENSE = VCS+ - VCS-
Full-Scale Sense Voltage
Total OUT Voltage Error
0
dB
1
mA
μA
1
150
mV
%
VSENSE= +100mV, VCC = 12V,
VCS+ = 12V, -40°C ≤ TA ≤ 85°C
1
4.25
VSENSE= +100mV, VCC = 12V,
VCS+ = 12V, TA = 125°C
1
4.5
VSENSE= +100mV, VCC = 12V,
VCS+ = +12V, TA = +25º
1
3 .2 5
VSENSE= +100mV, VCC = 25V,
VCS+ = 25V, -40°C ≤ TA ≤ 85°C
1
4.5
© 2005 Semtech Corp.
www.semtech.com
2
SC310
POWER MANAGEMENT
Electrical Characteristics (Cont.)
VCS+ = 2.7V to 25V, VCC = 3V to 25V, VSENSE = 0, TA = TJ = -40°C to +125°C , unless otherwise specified
P a r a met er
Symb ol
Total OUT Voltage Error
OUT High Voltage
3dB Bandwidth
G A IN
C on d i t i on s
Ty p
Ma x
Un i ts
VSENSE= +100mV, VCC = 25V,
VCS+ = 25V, TA = 125°C
1
4.75
%
VSENSE= +6.25mV, VCC =
12V, VCS+ = 12V, -40°C ≤
TA ≤ 125°C
+/- 7.5
1.7
V
VCC - VOH
-5°C ≤ TA ≤ +125°C
BW
SC310A, VSENSE = +100mV
2
SC310B, VSENSE = +100mV
1.4
SC310C, VSENSE = +100mV
0.9
SC310A
20
SC310B
50
SC310C
100
AV
Gain Accuracy
OUT Output Resistance (1)
Power-Supply Rejection
Mi n
VSENSE = +100mV,
SC310A/B/C
ROUT
VSENSE = +16mV
PSRR
VSENSE= 16mV
VCS+ > +2.7V
VCC = +12V
VCS+ = +12V
C L O A D= 5 p F
OUT Settling Time to 1% of
the Final Value
Power-Up Time to 1% of the
Final Value (2)
C
MHz
V/V
4.0
%
60
Ω
70
dB
VSENSE=
+6.25mV
to
+100mV
2
μS
VSENSE=
+100mV
to
+6.25mV
2
60
50
VSENSE= +100 mV,
= 5pF,VCC = +12V
LO A D
VCS+ = +12V
μS
Input bias current for SHDN
ISHDN
VSHDN = +5V
7
μA
VSHDN Threshold (device on)
VSHDN_TH_ON
3V ≤ Vcc ≤ 25V
350
mV
VSHDN Threshold (device of f)
VSHDN_TH_OFF
3V ≤ Vcc ≤ 25V
ICC
Vcc = 12V, VSHDN = +5V
Supply Current for SHDN
2
V
11
μA
Note (1): SC310 has a low impedence output. However the maximum output drive capability is limited to 500uA
Note (2): Defined with respect to Shutdown signal. Time taken for output to go high as VSHDN switches from 5V to 0V
© 2005 Semtech Corp.
www.semtech.com
3
SC310
POWER MANAGEMENT
Pin Configuration
Ordering Information
TOP VIEW
SHDN
1 6
OUT
GND
2 5
CS-
VCC
3 4
CS+
Device (1) (2) (3)
P ackag e
SC310XSKTRT
SOT-23-6
S C 310X E V B
Evaluation Board
Notes:
(1) Where X denotes Gain options. Available Gains are:
20 V/V (A), 50 V/V (B), 100 V/V (C). Contact factory for
additional voltage options.
(2) Only available in tape and reel packaging. A reel
contains 3000 devices.
(3) This lead-free device is fully RoHS and WEEE compliant.
(SOT-23 6L)
Pin Descriptions
SC310A, gain = 20 V/V
SC310B, gain = 50 V/V
SC310C, gain = 100 V/V
Pin
Name
Function
1
SHDN
Connect to GND to enable the IC
2
GND
Ground
3
VC C
Supply Voltage Input, bypass to ground with a 0.1µF capacitor
4
C S+
Power side connection to external sense resistor
5
C S-
Load side connection for the external sense resistor
6
OUT
Voltage output, VOUT is proportional to VSENSE (VCS+ - VCS-)
 2005 Semtech Corp.
www.semtech.com
4
SC310
POWER MANAGEMENT
Electrical Characteristics
VCS+ = 12V, VCC = 12V, VSENSE = 100mV, TA = 25°C, unless otherwise specified
Supply Current
T
v/s Supply Voltage
Bias Current v/s
Common-Mode Voltage
150
140
SC310C
0.3
SC310B
SC310A
0.2
Bias Current (uA)
Supply Current (mA)
0.4
0.1
130
SC310A
120
SC310B
110
SC310C
100
0
0
5
10
15
20
0
25
5
10
Supply Voltage (V)
Total Output Voltage Error
v/s Supply Voltage
20
25
Total Output Voltage Error
v/s Common-Mode Voltage
1
1.00
Total Output Error (%)
SC310C
Total Output Error (%)
15
Common-Mode Voltage (V)
0.8
0.6
SC310B
SC310A
0.4
0.2
0.60
5
10
15
20
SC310B
0.40
SC310C
0.20
0
0
SC310A
0.80
0.00
25
0
5
10
Supply Voltage (V)
15
20
25
Common-Mode Voltage (V)
SC310A Gain Accuracy
with Temperature
SC310B Gain Accuracy
with Temperature
1.6
1.2
1
1.2
-40 deg. C
Gain Accuracy (%)
Gain Accuracy (%)
1.4
1
0.8
Room Temp.
0.6
0.4
+85 deg. C
0.8
Room Temp
-40 deg. C
0.6
+85 deg. C
0.4
0.2
0.2
0
0
0
40
80
Sense Voltage (mV)
120
0
160
 2005 Semtech Corp.
40
80
Sense Voltage (mV)
120
160
www.semtech.com
5
SC310
POWER MANAGEMENT
Electrical Characteristics
VCS+ = 12V, VCC = 12V, VSENSE = 100mV, TA = 25°C, unless otherwise specified
SC310C Gain Accuracy
with Temperature
Bias Current v/s
Common-Mode Voltage in Shutdown
VSHDN = 5V
1
4
0.6
Bias Current (uA)
Gain Accuracy (%)
0.8
+85 deg. C
0.4
Room Temp.
0.2
-40 deg. C
0
3
2
1
-0.2
-0.4
0
0
-0.6
0
40
80
Sense Voltage (mV)
120
10
15
20
25
Common-Mode Voltage (V)
160
SC310B
SC310A
SC310C
Gain v/s Frequency
Supply Current
v/s Supply Voltage in Shutdown
VSHDN = 5V
6.00E+01
25
4.00E+01
20
Gain (dB)
Supply Current (uA)
5
15
2.00E+01
0.00E+00
10
-2.00E+01
5
-4.00E+01
1.00E+ 1.00E+ 1.00E+ 1.00E+ 1.00E+ 1.00E+ 1.00E+ 1.00E+
01
02
03
04
05
06
07
08
Frequency (Hz)
0
0
5
10
15
20
25
Supply Voltage (V)
SC310B
SC310A
SC310B
SC310C
SC310A
SC310C
PSRR v/s Frequency
1.0E+01
PSRR (dB)
-1.0E+01
-3.0E+01
-5.0E+01
-7.0E+01
-9.0E+01
1.0E+0 1.0E+0 1.0E+0 1.0E+0 1.0E+0 1.0E+0 1.0E+0 1.0E+0
1
2
3
4
5
6
7
8
Frequency
SC310B
SC310A
SC310C
 2005 Semtech Corp.
www.semtech.com
6
SC310
POWER MANAGEMENT
Electrical Characteristics (Cont.)
VCS+ = 12V, VCC = 12V, VSENSE = 100mV, TA = 25°C, unless otherwise specified
 2005 Semtech Corp.
www.semtech.com
7
SC310
POWER MANAGEMENT
Block Diagram
VCC
CS+
1k
CS-
Gain = A1
Gain = A2
Gain = A3
R4
R5
+
Q1
A
-
OUT
B
1k
-
R3
10k
SHDN
Gain = B
+
R1
20k
R2
5k
GND
Disable
Detailed Description
The SC310 has three gain versions as follows:
SC310 is a unidirectional high-side current sense amplifier for precision current monitoring. It has a wide common-mode range of 2.7 to 25V and allows high-side current-sensing at voltages greater than supply voltage (VCC).
The SC310 operates as follows: Current from source (as
shown in the typical applications circuit on page. 1), flows
through RSENSE to the load. Since the inverting input of
amplifier A has a high input impedance, negligible current flows through R5 (neglecting the input bias current).
Amplifier A has an inverting input voltage which equals
V(CS+) - ILOAD*RSENSE. The amplifier’s high open-loop gain
forces the non-inverting input voltage to the same voltage as the inverting input. The drop across R4 equals
I LOAD *R SENSE . Since I R4 flows through R4, IR4 =
(ILOAD*RSENSE)/R4. Resistor R3 then sets the overall gain
for amplifier A, A1, A2 or A3 (neglecting the input bias
currents for non-inverting inputs for amplifiers A and B).
The second amplifier, B, is a fixed gain stage (gain = B)
and the final output includes the gain obtained from this
stage.
 2005 Semtech Corp.
Version
Gain Exp ression
Gain Value
SC310A
A1*B
20
SC310B
A2*B
50
SC310C
A3*B
100
www.semtech.com
8
SC310
POWER MANAGEMENT
Application Information
Choosing R sense
Common Mode Input
Full scale sense voltage for the amplifier is 150mV max.
The resistor (Rsense) is selected depending on the load of
the system. For light loads a bigger value of Rsense is selected to minimize the error in the proportional output
voltage. Higher resistor value improves the strength of
the signal at the current-sense amplifier input and hence
gives an accurate output.
The sense voltage is limited at low values of common mode
input voltage (VCMR ). The figure below specifies the desired sense voltage for low common mode input voltage. In the figure below we see that SC310A can be operated over full-scale sense voltage at Vcs+ = 2.7V,
whereas the voltage is limited for SC310B and SC310C.
The voltage at the OUT pin of the amplifier is given as:
28V
Vout = (Gain) * (Iload) * (Rsense)
VCS+
Similarly, for heavy loads, a smaller value of Rsense resistor is used not to exceed the max “Sense Voltage” rating
of the IC. Also at high loads, a power rating of Rsense resistor is used and must be acceptable (greater than I2R
power dissipation in the resistor).
SC310C
SC310B
SC310A
5V
3.5V
PCB trace can also be used as the sense resistor. This
has the drawback of significant error at the output over
temperature. The trade-off, despite the error in the output voltage, provides for a cost-effective solution.
2.7V
0
35mV
70mV
150mV
V sense
SHDN FFunction
unction
Not drawn to scale
Layout Guidelines
The SHDN pin should not be kept floating and must be
tied to either ground or be held high. Connecting the pin
to ground is needed for normal operation. The voltage
level at the SHDN pin is independent of the functioning
of the IC.
1. Place the SC310 between the pins and external circuitry to reduce the trace length.
2. Place the decoupling capacitor at the input (VCC) as
close as possible to the pin.
3. An R-C filter at the input will help achieve the highest
noise rejection.
4. Run the traces from RSENSE as close as possible. Use
minimum width traces to reduce capacitive coupling.
Typical V
alues ffor
or Sense R
esist
or
Values
Resist
esistor
orss
Table 1. lists the common resistor values for typical operation of the SC310. SC310 is capable of sensing wide
ranges of currents providing proper sense resistors are
used.
Output Impedance
The output impedance of the SC310 is very low. Typical
value is 60Ω. Connecting the OUT pin to a high-impedance input stage is recommended. Resistive loading on
the OUT pin will not affect the gain of the SC310.
 2005 Semtech Corp.
www.semtech.com
9
SC310
POWER MANAGEMENT
Table 1. Recommended Component Values
Full-Scale Load Current
ILOAD (A)
0.1
1
2
5
10
Current Sense Resistor Rsense
(m
(mΩ)
1000
100
50
20
10
 2005 Semtech Corp.
Gain
Full-Scale Output Voltage
(Full-Scale V sense = 100mV)
V out (V)
20
2.0
50
5.0
100
10.0
20
2.0
50
5.0
100
10.0
20
2.0
50
5.0
100
10.0
20
2.0
50
5.0
100
10.0
20
2.0
50
5.0
100
10.0
www.semtech.com
10
SC310
POWER MANAGEMENT
Outline Drawing - SOT-23-6
DIM
A
e1
2X E/2
A
A1
A2
b
c
D
E1
E
e
e1
L
L1
N
01
aaa
bbb
ccc
D
N
EI
1
E
2
ccc C
2X N/2 TIPS
e
B
D
aaa C
A2
SEATING
PLANE
bxN
bbb
.057
.035
.006
.000
.035 .045 .051
.010
.020
.009
.003
.110 .114 .118
.060 .063 .069
.110 BSC
.037 BSC
.075 BSC
.012 .018 .024
(.024)
6
10°
0°
.004
.008
.008
1.45
0.90
0.00
0.15
.90 1.15 1.30
0.25
0.50
0.08
0.22
2.80 2.90 3.00
1.50 1.60 1.75
2.80 BSC
0.95 BSC
1.90 BSC
0.30 0.45 0.60
(0.60)
6
0°
10°
0.10
0.20
0.20
A
H
A1
C
DIMENSIONS
MILLIMETERS
INCHES
MIN NOM MAX MIN NOM MAX
H
c
GAGE
PLANE
C A-B D
0.25
L
01
(L1)
SEE DETAIL
A
DETAIL
A
SIDE VIEW
NOTES:
1.
CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
2. DATUMS -A- AND -B- TO BE DETERMINED AT DATUM PLANE -H3. DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS
OR GATE BURRS.
Land Pattern - SOT-23-6
X
DIM
(C)
G
Z
Y
P
C
G
P
X
Y
Z
DIMENSIONS
MILLIMETERS
INCHES
(.098)
.055
.037
.024
.043
.141
(2.50)
1.40
0.95
0.60
1.10
3.60
NOTES:
1.
THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY.
CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR
COMPANY'S MANUFACTURING GUIDELINES ARE MET.
 2005 Semtech Corp.
www.semtech.com
11
SC310
POWER MANAGEMENT
NOTES
Table 1. Recommended Component Values
Contact Information
Semtech Corporation
Power Management Products Division
200 Flynn Road, Camarillo, CA 93012
Phone: (805) 498-2111 FAX (805)498-3804
Visit us at: www.semtech.com
 2005 Semtech Corp.
www.semtech.com
12