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www.semtech.com 1 power management SC310 high-side current-sense amplifier with low impedance voltage output typical application circuit applications 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 applica- tions. 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 tem- perature range (-40c to +125c). 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 notebook and tablet pcs data acquisition battery packs charging applications industrial and embedded applications june 4, 2007 0.1uf 2.7v to 25v load/ battery cs+ cs- shdn out gnd vcc r sense i load v out 3v - 25v 0.1uf
2 ? 2005 semtech corp. www.semtech.com power management SC310 absolute maximum ratings electrical characteristics exceeding the specifications below may result in permanent damage to the device, or device malfunction. operation outside of th e parameters specified in the electrical characteristics section is not implied. v cs+ = 2.7v to 25v, v cc = 3v to 25v, v sense = 0, t a = t j = -40c to +125c , unless other wise specified r e t e m a r a pr e t e m a r a p r e t e m a r a p r e t e m a r a pr e t e m a r a pl o b m y sl o b m y s l o b m y s l o b m y sl o b m y ss n o i t i d n o cs n o i t i d n o c s n o i t i d n o c s n o i t i d n o cs n o i t i d n o cn i mn i m n i m n i mn i mp y tp y t p y t p y tp y tx a mx a m x a m x a mx a ms t i n us t i n u s t i n u s t i n us t i n u e g n a r e g a t l o v g n i t a r e p ov c c 35 2v e g n a r t u p n i e d o m - n o m m o cv r m c c 0 t a c 5 2 1 +7 . 25 2v c 0 4 - t a c 0 <3 5 2 n o i t c e j e r e d o m - n o m m o cr m c0 9b d t n e r r u c y l p p u si c c v + s c v , v 7 . 2 > c c v 2 1 =7 2 . 01a m t n e r r u c s a i b t u p n ii + s c v + s c v 7 . 2 + >0 5 1a i - s c v + s c v 7 . 2 + >01 e g a t l o v e s n e s e l a c s - l l u fv e s n e s v e s n e s v = + s c v - - s c 0 5 1v m r o r r e e g a t l o v t u o l a t o tv e s n e s v , v m 0 0 1 + = c c , v 2 1 = v + s c c 0 4 - , v 2 1 = t a c 5 8 15 2 . 4% v e s n e s v , v m 0 0 1 + = c c , v 2 1 = v + s c t , v 2 1 = a c 5 2 1 = 15 . 4 v e s n e s v , v m 0 0 1 + = c c , v 2 1 = v + s c t , v 2 1 + = a o 5 2 + = 15 2 . 3 v e s n e s v , v m 0 0 1 + = c c , v 5 2 = v + s c c 0 4 - , v 5 2 = t a c 5 8 15 . 4 parameter symbol min max units supply voltage vcc -0.3 28 v differential input voltage v cs+ - v cs- 0.5 v thermal resistance junction ja 230 c/w thermal resistance junction to case jc 81 c/w operating temperature range t a -40 +125 c storage temperature range t stg -65 +150 c junction temperature range t j -65 +150 c lead temperature (soldering) 10s t lead 260 c cs+ voltage v cs+ -0.3 vcc + 0.3 v cs- voltage v cs- -0.3 vcc + 0.3 v shdn voltage v shdn -0.3 vcc + 0.3 v esd rating (human body model) v esd 2 kv
3 ? 2005 semtech corp. www.semtech.com power management SC310 electrical characteristics (cont.) r e t e m a r a pr e t e m a r a p r e t e m a r a p r e t e m a r a pr e t e m a r a pl o b m y sl o b m y s l o b m y s l o b m y sl o b m y ss n o i t i d n o cs n o i t i d n o c s n o i t i d n o c s n o i t i d n o cs n o i t i d n o cn i mn i m n i m n i mn i mp y tp y t p y t p y tp y tx a mx a m x a m x a mx a ms t i n us t i n u s t i n u s t i n us t i n u r o r r e e g a t l o v t u o l a t o tv e s n e s v , v m 0 0 1 + = c c , v 5 2 = v + s c t , v 5 2 = a c 5 2 1 = 15 7 . 4% v e s n e s v , v m 5 2 . 6 + = c c = v , v 2 1 + s c c 0 4 - , v 2 1 = t a c 5 2 1 5 . 7 - / + e g a t l o v h g i h t u ov c c v - h o c 5 - t a c 5 2 1 +7 . 1v h t d i w d n a b b d 3w bv , a 0 1 3 c s e s n e s v m 0 0 1 + =2 v , b 0 1 3 c s e s n e s v m 0 0 1 + =4 . 1z h m v , c 0 1 3 c s e s n e s v m 0 0 1 + =9 . 0 n i a ga v a 0 1 3 c s0 2v / v b 0 1 3 c s0 5 c 0 1 3 c s0 0 1 y c a r u c c a n i a gv e s n e s , v m 0 0 1 + = c / b / a 0 1 3 c s 0 . 4% e c n a t s i s e r t u p t u o t u o ) 1 ( r t u o v e s n e s v m 6 1 + =0 6 n o i t c e j e r y l p p u s - r e w o pr r s pv e s n e s v m 6 1 = v + s c v 7 . 2 + > 0 60 7b d f o % 1 o t e m i t g n i l t t e s t u o e u l a v l a n i f e h t v c c v 2 1 + = v + s c v 2 1 + = c d a o l f p 5 = v e s n e s = v m 5 2 . 6 + o t v m 0 0 1 + 2s v e s n e s = v m 0 0 1 + o t v m 5 2 . 6 + 2 e h t f o % 1 o t e m i t p u - r e w o p e u l a v l a n i f ) 2 ( v e s n e s , v m 0 0 1 + = c d a o l v , f p 5 = c c v 2 1 + = v + s c v 2 1 + = 0 5s n d h s r o f t n e r r u c s a i b t u p n ii n d h s v n d h s v 5 + =7a v n d h s ) n o e c i v e d ( d l o h s e r h tv n o _ h t _ n d h s v 3 v c c v 5 20 5 3v m v n d h s ) f f o e c i v e d ( d l o h s e r h tv f f o _ h t _ n d h s v 3 v c c v 5 22 v n d h s r o f t n e r r u c y l p p u si c c v c c v , v 2 1 = n d h s v 5 + =1 1a 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 v shdn switches from 5v to 0v v cs+ = 2.7v to 25v, v cc = 3v to 25v, v sense = 0, t a = t j = -40c to +125c , unless other wise specified
4 ? 2005 semtech corp. www.semtech.com power management SC310 3 1 shdn top view (sot-23 6l) 5 cs- vcc 6 cs+ 4 out 2 gnd pin configuration ordering information e c i v e d ) 3 ( ) 2 ( ) 1 ( e g a k c a p t r t k s x 0 1 3 c s6 - 3 2 - t o s b v e x 0 1 3 c sd r a o b n o i t a u l a v e pin descriptions n i pe m a nn o i t c n u f 1n d h sc i e h t e l b a n e o t d n g o t t c e n n o c 2d n gd n u o r g 3c c v r o t i c a p a c f 1 . 0 a h t i w d n u o r g o t s s a p y b , t u p n i e g a t l o v y l p p u s 4+ s cr o t s i s e r e s n e s l a n r e t x e o t n o i t c e n n o c e d i s r e w o p 5- s cr o t s i s e r e s n e s l a n r e t x e e h t r o f n o i t c e n n o c e d i s d a o l 6t u ov , t u p t u o e g a t l o v t u o v o t l a n o i t r o p o r p s i e s n e s v ( + s c v - - s c ) SC310a, gain = 20 v/v SC310b, gain = 50 v/v SC310c, gain = 100 v/v 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 compli- ant.
5 ? 2005 semtech corp. www.semtech.com power management SC310 electrical characteristics t v cs+ = 12v, v cc = 12v, v sense = 100mv, t a = 25c, unless otherwise specified supply current v/s supply voltage 0 0.1 0.2 0.3 0.4 0 5 10 15 20 25 supply voltage (v) supply current (ma) SC310b SC310a SC310c bias current v/s common-mode voltage 100 110 120 130 140 150 0 5 10 15 20 25 common-mode voltage (v) bias current (ua) SC310a SC310b SC310c total output voltage error v/s supply voltage 0 0.2 0.4 0.6 0.8 1 0 5 10 15 20 25 supply voltage (v) total output error (%) SC310a SC310b SC310c total output voltage error v/s common-mode voltage 0.00 0.20 0.40 0.60 0.80 1.00 0 5 10 15 20 25 common-mode voltage (v) total output error (%) SC310c SC310 a SC310b SC310a gain accuracy with temperature 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0 40 80 120 160 sense voltage (mv) gain accuracy (%) -40 deg. c +85 deg. c room temp. SC310b gain accuracy with temperature 0 0.2 0.4 0.6 0.8 1 1.2 0 40 80 120 160 sense voltage (mv) gain accuracy (%) room temp +85 deg. c -40 deg. c
6 ? 2005 semtech corp. www.semtech.com power management SC310 electrical characteristics psrr v/s frequency -9.0e+01 -7.0e+01 -5.0e+01 -3.0e+01 -1.0e+01 1.0e+01 1.0e+0 1 1.0e+0 2 1.0e+0 3 1.0e+0 4 1.0e+0 5 1.0e+0 6 1.0e+0 7 1.0e+0 8 frequency psrr (db) SC310c SC310b SC310a gain v/s frequency -4.00e+01 -2.00e+01 0.00e+00 2.00e+01 4.00e+01 6.00e+01 1.00e+ 01 1.00e+ 02 1.00e+ 03 1.00e+ 04 1.00e+ 05 1.00e+ 06 1.00e+ 07 1.00e+ 08 frequency (hz) gain (db) SC310b SC310a SC310c v cs+ = 12v, v cc = 12v, v sense = 100mv, t a = 25c, unless otherwise specified SC310c gain accuracy with temperature -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 0 40 80 120 160 sense voltage (mv) gain accuracy (%) -40 deg. c room temp. +85 deg. c bias current v/s common-mode voltage in shutdown v shdn = 5v 0 1 2 3 4 0 5 10 15 20 25 common-mode voltage (v) bias current (ua) SC310b SC310a SC310c supply current v/s supply voltage in shutdown v shdn = 5v 0 5 10 15 20 25 0 5 10 15 20 25 supply voltage (v) supply current (ua) SC310b SC310a SC310c
7 ? 2005 semtech corp. www.semtech.com power management SC310 electrical characteristics (cont.) v cs+ = 12v, v cc = 12v, v sense = 100mv, t a = 25c, unless otherwise specified
8 ? 2005 semtech corp. www.semtech.com power management SC310 block diagram detailed description SC310 is a unidirectional high-side current sense ampli- fier for precision current monitoring. it has a wide com- mon-mode range of 2.7 to 25v and allows high-side cur- rent-sensing at voltages greater than supply voltage (v cc ). 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 cur- rent flows through r5 (neglecting the input bias current). amplifier a has an inverting input voltage which equals v(cs+) - i load *r sense . the amplifier?s high open-loop gain forces the non-inverting input voltage to the same volt- age as the inverting input. the drop across r4 equals i load *r sense . since i r4 flows through r4, ir4 = (i load *r sense )/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. n o i s r e vn o i s r e v n o i s r e v n o i s r e vn o i s r e vn o i s s e r p x e n i a gn o i s s e r p x e n i a g n o i s s e r p x e n i a g n o i s s e r p x e n i a gn o i s s e r p x e n i a ge u l a v n i a ge u l a v n i a g e u l a v n i a g e u l a v n i a ge u l a v n i a g a 0 1 3 c sb * 1 a0 2 b 0 1 3 c sb * 2 a0 5 c 0 1 3 c sb * 3 a0 0 1 the SC310 has three gain versions as follows: vcc + - + - r1 r2 r3 r4 r5 q1 a b gain = a1 gain = a2 gain = a3 gain = b cs- gnd shdn cs+ out 1k 10k 20k 5k 1k disable
9 ? 2005 semtech corp. www.semtech.com power management SC310 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 out- put voltage, provides for a cost-effective solution. shdn f shdn f shdn f shdn f shdn f unction unction unction unction 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. t t t t t ypical v ypical v ypical v ypical v ypical v alues f alues f alues f alues f alues f or sense r or sense r or sense r or sense r or sense r esist esist esist esist esist or or or or or s s s s s table 1. lists the common resistor values for typical op- eration of the SC310. SC310 is capable of sensing wide ranges of currents providing proper sense resistors are used. output impedance output impedance output impedance output impedance output impedance the output impedance of the SC310 is very low. typical value is 60 ? . connecting the out pin to a high-imped- ance input stage is recommended. resistive loading on the out pin will not affect the gain of the SC310. common mode input common mode input common mode input common mode input common mode input the sense voltage is limited at low values of common mode input voltage (v cmr ). the figure below specifies the de- sired sense voltage for low common mode input volt- age. in the figure below we see that SC310a can be op- erated over full-scale sense voltage at vcs+ = 2.7v, whereas the voltage is limited for SC310b and SC310c. layout guidelines layout guidelines layout guidelines layout guidelines layout guidelines 1. place the SC310 between the pins and external cir- cuitry to reduce the trace length. 2. place the decoupling capacitor at the input (v cc ) 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 r sense as close as possible. use minimum width traces to reduce capacitive coupling. choosing r choosing r choosing r choosing r choosing r sense sense sense sense sense full scale sense voltage for the amplifier is 150mv max. the resistor (r sense ) is selected depending on the load of the system. for light loads a bigger value of r sense is se- lected 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: v out = (gain) * (i load ) * (r sense ) similarly, for heavy loads, a smaller value of r sense resis- tor is used not to exceed the max ?sense voltage? rating of the ic. also at high loads, a power rating of r sense re- sistor is used and must be acceptable (greater than i 2 r power dissipation in the resistor). application information v sense 0 70mv 150mv 2.7v 3.5v 28v v cs+ 35mv 5v SC310c SC310b SC310a not drawn to scale
10 ? 2005 semtech corp. www.semtech.com power management SC310 t n e r r u c d a o l e l a c s - l l u ft n e r r u c d a o l e l a c s - l l u f t n e r r u c d a o l e l a c s - l l u f t n e r r u c d a o l e l a c s - l l u ft n e r r u c d a o l e l a c s - l l u f i i i ii d a o ld a o l d a o l d a o ld a o l ) a () a ( ) a ( ) a () a ( r r o t s i s e r e s n e s t n e r r u cr r o t s i s e r e s n e s t n e r r u c r r o t s i s e r e s n e s t n e r r u c r r o t s i s e r e s n e s t n e r r u cr r o t s i s e r e s n e s t n e r r u c e s n e se s n e s e s n e s e s n e se s n e s m (m ( m ( m (m ( ? ? ? ? ? ) ) ) ) ) n i a gn i a g n i a g n i a gn i a g e g a t l o v t u p t u o e l a c s - l l u fe g a t l o v t u p t u o e l a c s - l l u f e g a t l o v t u p t u o e l a c s - l l u f e g a t l o v t u p t u o e l a c s - l l u fe g a t l o v t u p t u o e l a c s - l l u f v e l a c s - l l u f (v e l a c s - l l u f ( v e l a c s - l l u f ( v e l a c s - l l u f (v e l a c s - l l u f ( e s n e se s n e s e s n e s e s n e se s n e s ) v m 0 0 1 =) v m 0 0 1 = ) v m 0 0 1 = ) v m 0 0 1 =) v m 0 0 1 = v v v v v t u ot u o t u o t u ot u o ) v () v ( ) v ( ) v () v ( 1 . 00 0 0 1 0 20 . 2 0 50 . 5 0 0 10 . 0 1 10 0 1 0 20 . 2 0 50 . 5 0 0 10 . 0 1 20 5 0 20 . 2 0 50 . 5 0 0 10 . 0 1 50 2 0 20 . 2 0 50 . 5 0 0 10 . 0 1 0 10 1 0 20 . 2 0 50 . 5 0 0 10 . 0 1 table 1. recommended component values
11 ? 2005 semtech corp. www.semtech.com power management SC310 outline drawing - sot-23-6 .110 bsc .037 bsc detail aaa c seating ccc c 2x n/2 tips 2x e/2 6 see detail a1 a a2 bxn a .008 12 n e .060 .114 .063 .118 .010 - 6 a 0.20 1.60 3.00 2.80 bsc 0.95 bsc .069 1.50 2.90 .020 0.25 1.75 0.50 - ei l (l1) c 01 0.25 plane gage h 2.80 .110 bbb c a-b d 0 .008 - .004 .012 .003 (.024) .018 - .035 .000 .035 - - .045 0.10 0.20 10 0 - 10 1.15 (0.60) 0.45 .024 .009 0.30 0.08 .057 .051 .006 0.00 .90 0.90 0.22 0.60 - 0.15 1.45 1.30 - - 1.90 bsc .075 bsc a e1 d e b c h nom inches dimensions l1 aaa bbb ccc 01 n dim c e e1 l e1 e d a1 a2 b a min millimeters max min nom max plane d datums and to be determined at datum plane controlling dimensions are in millimeters (angles in degrees). dimensions "e1" and "d" do not include mold flash, protrusions 3. or gate burrs. notes: 1. 2. -a- -b- -h- side view land pattern - sot-23-6 this land pattern is for reference purposes only. consult your manufacturing group to ensure your company's manufacturing guidelines are met. notes: 1. dimensions inches y z dim g p x c millimeters p (c) z y g .043 .141 .055 (.098) .037 .024 1.40 (2.50) 0.95 0.60 1.10 3.60 x dimensions inches y z dim g p x c millimeters
12 ? 2005 semtech corp. www.semtech.com power management SC310 table 1. recommended component values notes visit us at: www .semtech.com semtech corporation power management products division 200 flynn road, camarillo, ca 93012 phone: (805) 498-2111 fax (805)498-3804 contact information

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