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High-Side Current-Sense Amplifier with Low Impedance Voltage Output
POWER MANAGEMENT Description
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. 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. 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 (-40C to +125C).
SC310
Features
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 A supply current 1% typical accuracy Buffered low impedance voltage output Industrial temperature range (-40C to +125C) Small, lead-free SOT23-6 Package
Applications
Notebook and Tablet PCs Data Acquisition Battery Packs Charging Applications Industrial and Embedded Applications
Typical Application Circuit
R SENSE 2.7V to 25V
ILOAD
CS+
CS-
3V - 25V VCC SHDN 0.1uF OUT GND
V OUT
0.1uF
Load/ Battery
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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
Supply Voltage Differential Input Voltage Thermal Resistance Junction Thermal Resistance Junction to Case Operating Temperature Range Storage Temperature Range Junction Temperature Range Lead Temperature (Soldering) 10s CS+ Voltage CS- Voltage SHDN Voltage ESD Rating (Human Body Model)
Symbol
VCC VCS+ - VCSJA JC TA TSTG TJ TLEAD VCS+ VCSVSHDN VESD
Min
-0.3
Max
28 0.5 230 81
Units
V V C/W C/W C C C C V V V kV
-40 -65 -65
+125 +150 +150 260
-0.3 -0.3 -0.3
VCC + 0.3 VCC + 0.3 VCC + 0.3 2
Electrical Characteristics
VCS+ = 2.7V to 25V, VCC = 3V to 25V, VSENSE = 0, TA = TJ = -40C to +125C , unless otherwise specified
P a r a met er Operating Voltage Range Common-Mode Input Range
Symb ol VCC VCMR
C on d i t i on s
Mi n 3
Ty p
Ma x 25 25 25
Un i ts V V
0C TA +125C -40C TA < 0C
2.7 3 90
Common-Mode Rejection Supply Current Input Bias Current
CMR ICC ICS+ ICSVCS+ > 2.7V, VCC = 12V VCS+ > +2.7V VCS+ > +2.7V VSENSE = VCS+ - VCSVSENSE= +100mV, VCC = 12V, VCS+ = 12V, -40C TA 85C VSENSE= +100mV, VCC = 12V, VCS+ = 12V, TA = 125C VSENSE= +100mV, VCC = 12V, VCS+ = +12V, TA = +25 VSENSE= +100mV, VCC = 25V, VCS+ = 25V, -40C TA 85C 0
dB 1 mA A 1 150 mV %
0.27 150
Full-Scale Sense Voltage Total OUT Voltage Error
VSENSE
1 1 1 1
4.25 4.5 3 .2 5 4.5
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SC310
POWER MANAGEMENT Electrical Characteristics (Cont.)
VCS+ = 2.7V to 25V, VCC = 3V to 25V, VSENSE = 0, TA = TJ = -40C to +125C , unless otherwise specified
P a r a met er Total OUT Voltage Error
Symb ol
C on d i t i on s VSENSE= +100mV, VCC = 25V, VCS+ = 25V, TA = 125C VSENSE= +6.25mV, VCC = 12V, VCS+ = 12V, -40C TA 125C
Mi n
Ty p 1 +/- 7.5
Ma x 4.75
Un i ts %
OUT High Voltage 3dB Bandwidth
VCC - VOH BW
-5C TA +125C SC310A, VSENSE = +100mV SC310B, VSENSE = +100mV SC310C, VSENSE = +100mV 2 1.4 0.9 20 50 100
1.7
V
MHz
G A IN
AV
SC310A SC310B SC310C
V/V
Gain Accuracy OUT Output Resistance (1) Power-Supply Rejection OUT Settling Time to 1% of the Final Value ROUT PSRR
VSENSE = +100mV, SC310A/B/C VSENSE = +16mV VSENSE= 16mV VCS+ > +2.7V VCC = +12V VCS+ = +12V C L O A D= 5 p F VSENSE= +6.25mV to +100mV VSENSE= +100mV to +6.25mV 60 60 70 2
4.0
% dB S
2
Power-Up Time to 1% of the Final Value (2) Input bias current for SHDN VSHDN Threshold (device on) VSHDN Threshold (device of f) Supply Current for SHDN ISHDN VSHDN_TH_ON VSHDN_TH_OFF ICC
C
VSENSE= +100 mV, = 5pF,VCC = +12V LO A D VCS+ = +12V VSHDN = +5V 3V Vcc 25V 3V Vcc 25V 2
50
S
7 350
A mV V
Vcc = 12V, VSHDN = +5V
11
A
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
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SC310
POWER MANAGEMENT Pin Configuration Ordering Information
Device (1) (2) (3) P ackag e SOT-23-6 Evaluation Board
TOP VIEW
SHDN GND VCC 16 25 34 OUT CSCS+
SC310XSKTRT S C 310X E V B
(SOT-23 6L)
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.
Pin Descriptions
SC310A, gain = 20 V/V SC310B, gain = 50 V/V SC310C, gain = 100 V/V
Pin 1 2 3 4 5 6 Name SHDN GND VC C C S+ C SOUT Function Connect to GND to enable the IC Ground Supply Voltage Input, bypass to ground with a 0.1F capacitor Power side connection to external sense resistor Load side connection for the external sense resistor Voltage output, VOUT is proportional to VSENSE (VCS+ - VCS-)
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SC310
POWER MANAGEMENT Electrical Characteristics
VCS+ = 12V, VCC = 12V, VSENSE = 100mV, TA = 25C, unless otherwise specified
Supply Current T v/s Supply Voltage
0.4
150 140 Bias Current (uA) 130 120 110 100
Bias Current v/s Common-Mode Voltage
Supply Current (mA)
0.3 SC310A
SC310C SC310B
0.2
SC310A SC310B
0.1
SC310C
0 0 5 10 15 20 25 Supply Voltage (V)
0
5
10
15
20
25
Common-Mode Voltage (V)
Total Output Voltage Error v/s Supply Voltage
1 Total Output Error (%) 0.8 0.6
SC310A SC310B
Total Output Voltage Error v/s Common-Mode Voltage
1.00 Total Output Error (%)
SC310C
0.80 0.60 0.40 0.20 0.00 0 5 10
SC310C
SC310A
SC310B
0.4 0.2 0 0 5 10 15 20 25 Supply Voltage (V)
15
20
25
Common-Mode Voltage (V)
SC310A Gain Accuracy with Temperature
1.6 1.4 Gain Accuracy (%)
SC310B Gain Accuracy with Temperature
1.2 1 Gain Accuracy (%)
1.2 1 0.8 0.6 0.4 0.2 0 0
-40 deg. C
0.8 Room Temp 0.6 0.4 0.2 0 +85 deg. C -40 deg. C
Room Temp.
+85 deg. C
40
80 Sense Voltage (mV)
120
160
0
40
80 Sense Voltage (mV)
120
160
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SC310
POWER MANAGEMENT Electrical Characteristics
VCS+ = 12V, VCC = 12V, VSENSE = 100mV, TA = 25C, unless otherwise specified
SC310C Gain Accuracy with Temperature
1 0.8 Gain Accuracy (%) +85 deg. C Room Temp. -40 deg. C
Bias Current (uA) 4
Bias Current v/s Common-Mode Voltage in Shutdown VSHDN = 5V
0.6 0.4 0.2 0 -0.2 -0.4 -0.6 0 40
3
2
1
0 0 5 10 SC310B SC310A 15 SC310C 20 25
80 Sense Voltage (mV)
120
160
Common-Mode Voltage (V)
Supply Current v/s Supply Voltage in Shutdown VSHDN = 5V
25 Supply Current (uA) 20 15 10
Gain v/s Frequency
6.00E+01 4.00E+01 Gain (dB) 2.00E+01 0.00E+00 -2.00E+01
5 0 0 5 10 SC310B SC310A 15 SC310C 20 25 Supply Voltage (V)
-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)
SC310B SC310A SC310C
PSRR v/s Frequency 1.0E+01 -1.0E+01 PSRR (dB) -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
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SC310
POWER MANAGEMENT Electrical Characteristics (Cont.)
VCS+ = 12V, VCC = 12V, VSENSE = 100mV, TA = 25C, unless otherwise specified
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SC310
POWER MANAGEMENT Block Diagram
VCC
CS+
R4 1k
+
Gain = A1 Gain = A2 Gain = A3
A
-
Q1
+ Gain = B
CS-
R5 1k
B
-
OUT R1 20k
R3 10k
R2 SHDN Disable
5k GND
Detailed Description
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. The SC310 has three gain versions as follows:
Version SC310A SC310B SC310C Gain Exp ression A1*B A2*B A3*B Gain Value 20 50 100
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SC310
POWER MANAGEMENT Application Information
Choosing R sense 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 voltage at the OUT pin of the amplifier is given as: Vout = (Gain) * (Iload) * (Rsense) 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). 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. Function SHDN F unction 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. Values for Resistors esistor Typical V alues f or Sense R esist or s 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 60. 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.
VCS+ SC310C SC310B SC310A
5V 3.5V 2.7V
Common Mode Input 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.
28V
0
35mV
70mV
150mV
V sense
Not drawn to scale
Layout Guidelines 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.
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SC310
POWER MANAGEMENT Table 1. Recommended Component Values
Full-Scale Load Current ILOAD (A) Current Sense Resistor Rsense (m) (m Gain 20 0.1 1000 50 100 20 1 100 50 100 20 2 50 50 100 20 5 20 50 100 20 10 10 50 100 Full-Scale Output Voltage (Full-Scale V sense = 100mV) V out (V) 2.0 5.0 10.0 2.0 5.0 10.0 2.0 5.0 10.0 2.0 5.0 10.0 2.0 5.0 10.0
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SC310
POWER MANAGEMENT Outline Drawing - SOT-23-6
DIM
e1 N EI 1 ccc C 2X N/2 TIPS B 2 E D
A A1 A2 b c D E1 E e e1 L L1 N 01 aaa bbb ccc
A
DIMENSIONS MILLIMETERS INCHES MIN NOM MAX MIN NOM MAX
.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
2X E/2
e
D aaa C A2 SEATING PLANE C A1 bxN bbb C A-B D A
H GAGE PLANE 0.25
H c
L (L1)
01
SEE DETAIL SIDE VIEW
NOTES: 1.
A
DETAIL
A
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 Y P Z 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.
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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
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