View SC820-1_8641263.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

? 2009 semtech corporation power management 1 sc820 adapter/usb dual input single-cell li-ion charger features input voltage protection 30v adapter input automatically selected over usb constant voltage 4.2v, 1% regulation charging by current and voltage regulation (cc/cv) thermal limiting of charge current programmable battery-dependent currents (adapter- sourced fast-charge & pre-charge, termination) programmable source-limited currents (usb-sourced fast-charge & pre-charge) current-limited adapter support reduces power dis- sipation in charger ic usb input limits charge current prevents vbus overload instantaneous cc-to-cv transition for faster charging three termination options fl oat-charge, automatic re-charge, or forced re-charge to keep the battery topped-off after termination without fl oat-charging soft-start reduces load transients high operating voltage range permits use of unregulated adapters complies with ccsa yd/t 1591-2006 space saving 220.6 (mm) mlpd package pb free, halogen free, and rohs/weee compliant applications mobile phones mp3 players gps handheld receivers ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? description the sc820 is a dual input (adapter/usb) linear single-cell li-ion battery charger in an 8 lead 22mm mlpd ultra-thin package. both inputs will survive sustained input voltage up to 30v to protect against hot plug overshoot and faulty charging adapters. charging begins automatically when a valid input source is applied to either input. the adapter input is selected when both input sources are present. thermal limiting protects the sc820 from excessive power dissipation when charging from either source. the sc820 can be programmed to turn off when charging is complete or to continue operating as an ldo regulator while fl oat- charging the battery. the adapter input charges with an adapter operating in voltage regulation or in current limit to obtain the lowest possible power dissipation by pulling the vad input voltage down to the battery voltage. the vusb input dynamically limits load current to automatically prevent over-loading the usb vbus supply. charge current programming requires two resistors. one determines battery-capacity dependent currents: adapter input fast-charge current, pre-charge current, and charge termination current. the other independently determines input-limited usb charging currents: usb input fast- charge and pre-charge current. device load battery pack 2.2 f usb vbus 2.2 f v adapter 2.2 f ipusb iprgm vusb sc820 gnd statb enb bat vad typical application circuit september 17, 2009
sc820 2 pin confi guration marking information ordering information device package sc820ultrt (1)(2) mlpd-ut-8 22 sc820evb evaluation board notes: (1) available in tape and reel only. a reel contains 3,000 devices. (2) pb free, halogen free, and rohs/weee compliant. top view t 1 2 4 5 6 3 7 8 enb bat iprgm vad statb gnd ipusb vusb 820 yw mlpd-ut8; 22, 8 lead ja = 68c/w yw = date code
sc820 3 exceeding the above specifi cations may result in permanent damage to the devic e or device malfunction. operation outside of the parameters specifi ed in the electrical characteristics section is not recommended. notes: (1) tested according to jedec standard jesd22-a114d. (2) operating voltage is the input voltage at which the charger is guaranteed to begin oper ation. these ranges, vt adsel-r max to v ovp-f min for the vad input, v uvlr max to v ovp-f min for the vusb input, apply to charging sources oper ating in voltage regulation. charging sources operating in current limit may be pulled below these ranges by the charging load. maximum operating voltage is the maximum vsupply as de fined in eia/jedec standard no. 78, paragraph 2.11. (3) calculated from package in still air, mounted to 3 x 4.5 (in), 4 layer fr4 pcb with thermal vias under the exposed pad per jesd51 standards. absolute maximum ratings vad and vusb (v) . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to +30.0 bat, iprgm, ipusb (v) . . . . . . . . . . . . . . . . . . . . . . -0.3 to +6.5 statb, enb (v) . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to v bat +0.3 vad input current (a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . 5 vusb input current (a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . 5 bat, iprgm, ipusb short-to-gnd duration . . . . . continuous esd protection level (1) (kv) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 recommended operating conditions operating ambient tempera ture (c) . . . . . . . . . -40 to +85 vad operating voltage (2) (v) . . . . . . . . . . . . . . . . 4.60 to 8.20 vusb operating voltage (2) (v) . . . . . . . . . . . . . . . 4.70 to 8.20 thermal information thermal resistance, junction to ambient (3) (c/w) . . . . . 68 maximum junction temperature (c) . . . . . . . . . . . . . . +150 storage temperature range (c) . . . . . . . . . . . . -65 to +150 peak ir reflow temperature (10s to 30s) (c) . . . . . . . +260 test conditions: v vad = v vusb = 4.75v to 5.25v; c vad = c vusb = c bat = 2.2f; v bat = 3.7v; typ values at 25c; min and max at -40c < t a < 85c, unless specifi ed. parameter symbol conditions min typ max units vad select rising threshold vt adsel-r 4.30 4.45 4.60 v vad deselect falling threshold (1) vt adsel-f v vad > v bat 2.70 2.85 3.00 v vusb select rising threshold vt usbsel-r v vusb > v bat 4.20 4.35 v vusb deselect falling threshold vt usbsel-f v vusb > v bat 3.65 4.00 v vusb select hysteresis vt usbsel-h vt usbsel-r - vt usbsel-f 100 mv ovp rising threshold vt ovp-r vad or vusb input 9.6 v ovp falling threshold vt ovp-f vad or vusb input 8.2 v ovp hysteresis vt ovp-h (vt ovp-r - vt ovp-f )50 mv vad charging disabled quiescent current iq vad_dis v vusb = 0v, v enb = v bat 23ma vad charging enabled quiescent current iq vad_en v vusb = 0v, v enb = 0v, excluding i bat , i iprgm , and i ipusb 23ma vusb charging disabled quiescent current iq vusb_dis v vad = 0v; v enb = v bat 23ma electrical characteristics
sc820 4 parameter symbol conditions min typ max units vusb charging enabled quiescent current iq vusb_en v vad = 0v, v enb = 0v, excluding i bat , i iprgm , and i ipusb 23ma vusb deselected quiescent current (2) iq vusb_des v vad v vusb 25 50 a cv regulation voltage v cv i bat = 50ma, -40c t j 125c 4.16 4.20 4.24 v cv voltage load regulation (3) v cv_load relative to v cv @ 50ma, v vad = 5v, or v vusb = 5v and v vad = 0v, 1ma i bat 700ma, -40c t j 125c -20 10 mv re-charge threshold vt req v cv v bat 60 100 140 mv pre-charge threshold (rising) vt preq 2.85 2.90 2.95 v battery leakage current l bat_v0 v bat = v cv , v vad = v vusb = 0v 0.1 1 a l bat_dis v bat = v cv , v vad = v vusb = 5v, v enb = 2v 0.1 1 a l bat_mon v bat = v cv , v vad = v vusb = 5v, enb not connected 0.1 1 a iprgm programming resistor r iprgm 2.05 29.4 k fast-charge current, vad input i fq_ad r iprgm = 2.94k, vt preq < v bat < v cv 643 694 745 ma pre-charge current, vad input i preq_ad r iprgm = 2.94k, 1.8v < v bat < vt preq 105 139 173 ma termination current, either input i term r iprgm = 2.94k, v bat = v cv 59 69 80 ma vad to bat dropout voltage v do_ad i bat = 700ma, 0c t j 125c 0.75 1.0 v ipusb programming resistor r ipusb 4.42 29.4 k fast-charge current, vusb input i fq_usb r ipusb = 4.42k, vt preq < v bat < v cv 427 462 497 ma pre-charge current, vusb input i preq_usb r ipusb = 4.42k, 1.8v < v bat < vt preq 69 92 116 ma vusb to bat dropout voltage v do_usb i bat = 500ma, 0c t j 125c 0.55 1 v iprgm fast-charge regulated voltage v iprgm_fq v vad = 5.0v, v vusb = 0v, vt preq < v bat < v cv 2.04 v iprgm pre-charge regulated voltage v iprgm_pq v bat < vt preq 0.408 v iprgm termination threshold voltage vt iprgm_term v bat = v cv (either input selected) 0.204 v ipusb fast-charge regulated voltage v ipusb_fq v vad = 0v, vt preq < v bat < v cv 2.04 v ipusb pre-charge regulated voltage v ipusb_pq v vad = 0v, v bat < vt preq 0.408 v vusb under-voltage load regulation limiting voltage v uvlr 5ma vusb supply current limit 500ma, v vad = 0v, r ipusb = 3.65k (559ma) 4.40 4.57 4.70 v electrical characteristics (continued)
sc820 5 electrical characteristics (continued) parameter symbol conditions min typ max units thermal limiting threshold tempera- ture t tl 130 c thermal limiting rate i t t j > t tl -50 ma/ c enb input high voltage v ih 1.6 v enb input mid voltage v im 0.7 1.3 v enb input low voltage v il 0.3 v enb input high-range threshold input current i ih_th enb current required to pull enb from floating midrange into high range 23 50 a enb input high-range sustain input current i ih_sus current required to hold enb in high range, min v ih v enb v bat , min v ih v bat 4.2v 0.3 1 a enb input mid-range load limit i im input will float to mid range when this load limit is observed. -5 5 a enb input low-range input current i il 0v v enb max v il -25 -12 a enb input leakage i ileak v vin = 0v, v enb = v bat = 4.2v 1 a statb output low voltage v stat_lo i stat_sink = 2ma 0.5 v statb output high current i stat_hi v stat = 5v 1 a notes: (1) sustained operation to vt adsel-f v vad is guaranteed only if a current limited charging source applied to vad is pulled below vt adsel-r by the charging load; forced vad voltage below vt adsel-r may in some cases result in regulation errors or other unexpected behavior. (2) if vad is the selected input but v vad < v vusb , such as when vad is operating with an adapter in current limit while a vusb charging source is applied, iq vusb_des will increase to approximately iq vusb_en . (3) at load currents exceeding 700ma, or at 700ma while at elevated ambient temperature, the charger may enter dropout with a 5 v input before the battery voltage has risen to v cv . see the specifi cation of v do_ad . although this is a safe and acceptable mode of operation, specifi cation of v cv when in dropout is not applicable; higher input voltage will restore the charger to cv regulation in these cases. note that v bat is always less than v cv while in dropout. as the battery state-of-charge increases, the charging current will decrease allowing the battery voltage t o rise to v cv , and cv regulation will begin. this appears as a softening or rounding of the cc-to-cv regulation mode transition, similar to that seen in chargers with a linear cc-to-cv regulation crossover.
sc820 6 typical characteristics cv line regulation cv load regulation cv temperature regulation cc fq line regulation (ad or usb) cc fq v bat regulation (ad or usb) cc fq temperature regulation (ad or usb) 55.566.577.58 4.18 4.184 4.188 4.192 4.196 4.2 4.204 v vad (v) v bat (v) t a = 25 c, i bat = 50ma 0 100 200 300 400 500 600 700 800 4.18 4.184 4.188 4.192 4.196 4.2 4.204 i bat (ma) v bat (v) t a = 25 c, v vad = 5v -40 -20 0 20 40 60 80 100 120 4.18 4.184 4.188 4.192 4.196 4.2 4.204 ambient temperature ( o c) v bat (v) v vad = 5v, i bat = 50ma 4.5 5 5.5 6 6.5 7 7.5 8 440 480 520 560 600 640 680 720 r iprgm or r ipusb = 2.94k r iprgm or r ipusb = 4.42k v vad (v) i bat (ma) t a = 25 c, v bat = 3.7v 2.9 3.1 3.3 3.5 3.7 3.9 4.1 440 480 520 560 600 640 680 720 v bat (v) i bat (ma) t a = 25 c, v vad = 5v r iprgm or r ipusb = 2.94k r iprgm or r ipusb = 4.42k -40 -20 0 20 40 60 80 100 120 440 480 520 560 600 640 680 720 ambient temperature ( o c) i bat (ma) v vad = 5v, v bat = 3.7v
sc820 7 typical characteristics (continued) cc pq line regulation (ad or usb) cc pq temperature regulation (ad or usb) i fq_ad vs. r iprgm , or i fq_usb vs. r ipusb i pq_ad vs. r iprgm , or i pq_usb vs. r ipusb cc input reselection, ad to usb cc input reselection, usb to ad 55.566.577.58 90 100 110 120 130 140 150 160 v vad (v) i bat (ma) t a = 25 c, v bat = 2.6v r iprgm or r ipusb = 2.94k r iprgm or r ipusb = 4.42k -40 -20 0 20 40 60 80 100 120 90 100 110 120 130 140 150 160 ambient temperature ( o c) i bat (ma) v vad = 5v, v bat = 2.6v r iprgm or r ipusb = 2.94k r iprgm or r ipusb = 4.42k 2 6 10 14 18 22 26 30 0 200 400 600 800 1000 r iprgm or r ipusb (k ) i bat (ma) v vad = 5v, v bat = 3.7v, t a = 25 c 2 6 10 14 18 22 26 30 0 40 80 120 160 200 r iprgm or r ipusb (k ) i bat (ma) v vad = 5v, v bat = 2.6v, t a = 25 c 400 s/div v vad (1.0v/div) v vad =0v i bat (200ma/div) i bat =0ma v bat =3.7v, v vusb =5.0v 400 s/div v vad (1.0v/div) v vad =0v i bat (200ma/div) i bat =0ma v bat =3.7v, v vusb =5.0v
sc820 8 typical characteristics (continued) charging cycle battery voltage and current pre-charging battery voltage and current cc-to-cv battery voltage and current re-charge cycle battery voltage and current 0 100 200 300 400 500 600 700 i bat (ma) 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 0 1 2 3 4 5 6 7 time (hrs) v bat (v) 850mahr battery, r iprgm = 2.94k , v vad = 5.0v, t a = 25 c v bat i bat 0 100 200 300 400 500 600 700 800 i bat (ma) 0 2 4 6 8 101214161820 2 2.25 2.5 2.75 3 3.25 3.5 3.75 4 time (s) v bat (v) 850mahr battery, r iprgm = 2.94k , v vad = 5.0v, t a = 25 c v bat i bat 610 630 650 670 690 710 i bat (ma) 44 44.5 45 45.5 46 46.5 47 47.5 48 4.16 4.17 4.18 4.19 4.2 4.21 time (min) v bat (v) 850mahr battery, r iprgm = 2.94k , v vad = 5.0v, t a = 25 c v bat i bat 0 50 100 150 200 250 300 350 400 450 i bat (ma) 0.0 0.5 1.0 1.5 2/6 6.5 7.0 7.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 time (hrs) v bat (v) 850mahr battery, r iprgm = 2.94k , v vad = 5.0v, load = 10ma v bat i bat discharge hours 2 - 6 omitted.
sc820 9 pin descriptions pin # pin name pin function 1vad supply pin connect to charging adapter. this pin is protected against damage due to high voltage up to 30v. 2 vusb supply pin connect to usb vbus power. typically 5v, limited load-current input. this pin is protected against damage due to high voltage up to 30v. 3statb status output pin this open-drain pin is asserted (pulled low) when a valid charging supply is connected to either vad or vusb, and a charging cycle begins. it is released when the termination current is reached, indicating that charging is complete. statb is not asserted for re-charge cycles. 4 gnd ground 5 ipusb fast-charge and pre-charge current programming pin for the vusb power source vusb fast-charge current is programmed by connecting a resistor from this pin to ground. vusb pre-charge current is 20% of fast-charge current. 6 iprgm fast-charge and pre-charge current programming pin for the adapter power source vad fast-charge current is programmed by connecting a resistor from this pin to ground. vad pre-charge current is 20% of fast-charge current. the charging termination threshold current (for either vad or vusb input selection) is 10% of the iprgm programmed fast-charge current. 7bat charger output connect to battery positive terminal. 8 enb combined device enable/disable logic high disables the device. tie to gnd to enable charging with indefi nite fl oat-charging. float this pin to enable charging without fl oat-charge upon termination. note that this pin must be grounded if the sc820 is to be operated without a battery connected to bat. t thermal pad pad is for heatsinking purposes not connected internally. connect exposed pad to ground plane using mul- tiple vias.
sc820 10 block diagram cc cv input selection logic ad/usb select termination statb enb iprgm gnd bat ipusb vad vusb v_adapter usb_vbus 1 2 4 8 3 to system load lithium- ion single cell battery pack r iprgm r ipusb connect to bat or to regulated supply 6 7 vt iprgm_term v cv = 4.2v v iref v vusb_uv_lim = 4.57v pre-charge, cc/ cv & termination controller, logical state machine cc feedback selection tri-level control vt enb_high = ~1.50v vt enb_low = ~0.55 1v thermal limiting die temperature v t_ct 5 regulated system supply
sc820 11 charger operation the sc820 is a dual-input stand-alone li-ion battery charger. the vad input pin is optimized for a charging adapter. the vusb pin is optimized for charging from the usb vbus supply. the device is independently pro- grammed for battery-capacity-dependent currents (adapter fast-charge current and termination current) using the iprgm pin. charging currents from the usb vbus supply, which has a maximum load specifi cation, are programmed using the ipusb pin. when a valid input supply is fi rst detected, a charge cycle is initiated and the statb open-drain output goes low. if the battery voltage is less than the pre-charge threshold voltage, the pre-charge current is supplied. pre-charge current is 20% of the programmed fast-charge current for the selected input. when the battery voltage exceeds the pre-charge thresh- old, typically within seconds for a standard battery with a starting cell voltage greater than 2v, the fast-charge constant current (cc) mode begins. the charge current soft-starts in three steps (20%, 60%, and 100% of pro- grammed fast-charge current) to reduce adapter load transients. cc current is programmed by the iprgm resis- tance to ground when the vad input is selected and by the ipusb resistance to ground when the vusb input is selected. the charger begins constant voltage (cv) regulation when the battery voltage rises to the fully-charged single- cell li-ion regulation voltage (v cv ), nominally 4.2v. in cv regulation, the output voltage is regulated, and as the battery charges, the charge current gradually decreases. the statb output goes high when i bat drops below the termination threshold current, which is 10% of the iprgm pin programmed fast-charge current regardless of the input selected. this is known as charge termination. optional float-charging or monitoring depending on the state of the enb input, upon termina- tion the sc820 either operates indefi nitely as a voltage regulator (fl oat-charging) or it turns off its output. if the output is turned off upon termination, the device enters the monitor state. in this state, the output remains off until the bat pin voltage decreases by the re-charge threshold (vt req = 100mv typically). a re-charge cycle then begins automatically and the process repeats. a forced re-charge cycle can also be periodically commanded by the proces- sor to keep the battery topped-off without fl oat-charging. see the monitor state section for details. re-charge cycles are not indicated by the statb pin. charging input selection the sc820 has two charging supply input pins. vad is optimized for adapter charging. vusb is optimized for charging from the usb vbus power supply. the inputs diff er in selection rising and de-selection falling thresh- olds, their behavior when overloading their respective charging sources, and in which current programming pin determines the fast-charge and pre-charge current. both use the same over-voltage protection (ovp) threshold. glitch fi ltering is performed on the vad and vusb inputs, so an applied input voltage that is ringing across its selec- tion threshold will not be selected until the ringing has ceased. when both inputs exceed their respective uvlo thresholds, vad is selected even when vad voltage is applied while already charging from the vusb input. vad is also selected in the case that the vad voltage exceeds its ovp threshold, so that an excessive vad voltage will disable charging despite the presence of a valid vusb input voltage. when a valid input (defi ned as greater than its selection threshold and less than the ovp threshold) is first selected, a charge cycle is initiated and the statb output is asserted. when a new input selection is made (when vad is applied or removed while vusb is present), the charge cycle is immediately halted and re-initiated with the newly selected input. there is a momentary (approxi- mately 1ms) interruption in output current and a release and re-assertion of the statb pin during input res-election. if the vad input charging current loads the adapter beyond its current limit, the vad input voltage will be pulled down to just above the battery voltage. this is referred to as current-limit ed-adapter (cla) operation. the adapter input de-selection falling threshold is set close to the battery voltage pre-charge threshold to permit low-dissipation charging from a current limited adapter. applications information
sc820 12 applications information (continued) the vusb input provides a higher de-selection falling threshold appropriate to the usb specifi cation. the usb input also provides under-voltage load regulation (uvlr), in which the charging current is reduced if needed to prevent overloading of the usb vbus supply. uvlr can serve as a low-cost alternative to directly programming the usb low power charge current (by switching the ipusb resistor), or where there is no signal available to indicate whether usb low or high power mode should be selected. constant current mode fast-charge current programming the constant current (cc) mode is active when the battery voltage is above the pre-charge threshold voltage (vt preq ) and less than v cv . when vad is the selected input, the programmed cc regulation fast-charge (fq) current is inversely proportional to the iprgm pin resistance to gnd according to the equation 5 9 , ,35*0 7\s b ,35*0 $' b )4 when vusb is the selected input, the programmed cc mode fast-charge current is inversely proportional to the ipusb pin resistance to gnd according to the equation 5 9 , ,386% 7\s b ,386% 86% b )4 the nominal fast-charge current for either input can be programmed to the minimum of 70ma (r ipxxx = 29.4k). the maximum fast-charge current for the vad input is 995ma nominally (r iprgm = 2.05k), and for the vusb input, the programmed fast-charge current should not exceed 450ma (r ipusb = 4.42k) nominally. (if a greater usb input fast-charge current is desired, please contact your semtech field applications engineer for assistance.) the vad input is designed for lower dropout voltage at high current, which ensures charging without thermal limiting with a charging adapter operating in current limit of at least 700ma. current regulation accuracy is dominated by gain error at high current settings and o set error at low current set- tings. the range of expected fast-charge output current versus programming resistance r iprgm or r ipusb (for vad or vusb input selected, respectively) is shown in figures 1a and 1b. the figures show the nominal current versus nominal r iprgm or r ipusb resistance as the center plot and two theoretical limit plots indicating maximum and minimum current versus nominal programming resis- tance. these plots are derived from models of the expected worst-case contribution of error sources depending on programmed current. the current range 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100 r iprgm or r ipusb (k ), r-tol = 1% fast-charge current (ma) figure 1a fast-charge current tolerance versus programming resistance, low resistance range 7 8 9 1011121314151617181920212223242526272829 50 75 100 125 150 175 200 225 250 275 300 325 r iprgm or r ipusb (k ), r-tol = 1% fast-charge current (ma) figure 1b fast-charge current tolerance versus programming resistance, high resistance range
sc820 13 includes the uncertainty due to 1% tolerance resistors. the dots on each plot indicate the currents obtained with the electronic industries association (eia) e96 standard value 1% tolerance resistors. figures 1a and 1b show low and high resistance ranges, respectively. pre-charge mode this mode is automatically enabled when the battery voltage is below the pre-charge threshold voltage (vt preq ), typically 2.9v. pre-charge current conditions the battery for fast charging. the pre-charge current value is fi xed at 20% nominally of the fast-charge current for the selected input. the fast-charge current is programmed by the resistance between iprgm and gnd for the vad input, and by the resistance between ipusb and gnd for the vusb input. pre-charge current regulation accuracy is dominated by offset error. the range of expected pre-charge output current versus programming resistance is shown in figures 2a and 2b. the figures show the nominal pre-charge current versus nominal resistance as the center plot and two theoretical limit plots indicating maximum and minimum current versus nominal programming resis- tance. these plots are derived from models of the expected worst-case contribution of error sources depending on programmed current. the current range includes the uncertainty due to 1% tolerance resistors. the dots on each plot indicate the currents obtained with the electronic industries association (eia) e96 standard applications information (continued) value 1% tolerance resistors. figures 2a and 2b show low and high resistance ranges, respectively. termination when the battery voltage reaches v cv , the sc820 transi- tions from constant current regulation to constant voltage regulation. while v bat is regulated to v cv , the current into the battery decreases as the battery becomes fully charged. when the output current drops below the termination threshold current, charging terminates. upon termination, the statb pin open drain output turns off and the charger either enters monitor state or fl oat- charges the battery, depending on the logical state of the enb input pin. the termination threshold current is fi xed at 10% of the vad input fast-charge current, as programmed by the resistance between iprgm and gnd. the iprgm pin resistance determines the termination threshold current regardless of whether the selected charging input is vad or vusb. charger output current is the sum of the battery charge current and the system load current. battery charge current changes gradually, and establishes a slowly diminishing lower bound on the output current while charging in cv mode. the load current into a typical digital system is highly transient in nature. charge cycle termination is detected when the sum of the battery charging current and the greatest load current occurring figure 2a pre-charge current tolerance versus programming resistance, low resistance range 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 r iprgm or r ipusb (k ), r-tol = 1% pre-charge current (ma) figure 2b pre-charge current tolerance versus programming resistance, high resistance range 7 8 9 1011121314151617181920212223242526272829 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 r iprgm or r ipusb (k ), r-tol = 1% pre-charge current (ma)
sc820 14 applications information (continued) within the immediate 300s to 550s past interval is less than the programmed termination current. this timing behavior permits charge cycle termination to occur during a brief low-load-current interval, and does not require that the longer interval average load current be small. termination threshold current accuracy is dominated by off set error. the range of expected termination current versus programming resistance r iprgm (for either vad or vusb input selected) is shown in figures 3a and 3b. the figures show the nominal termination current versus nominal r iprgm resistance as the center plot and two theo- retical limit plots indicating maximum and minimum current versus nominal programming resistance. these plots are derived from models of the expected worst-case contribution of error sources depending on programmed current. the current range includes the uncertainty due to a 1% tolerance resistor. the dots on each plot indicate the currents obtained with the electronic industries association (eia) e96 standard value 1% tolerance resis- tors. figures 3a and 3b show low and high resistance ranges, respectively. enable input the enb pin is a tri-level logical input that allows selection of the following behaviors: charging enabled with fl oat-charging after ter- mination (enb = low range) ? charging enabled with fl oat-charging disabled and battery monitoring at termination (enb = mid range) charging disabled (enb = high range). this input is designed to interface to a processor gpio port powered from a peripheral supply voltage as low as 1.8v or as high as a fully charged battery. while a con- nected gpio port is confi gured as an output, the proces- sor writes a 0 to select enb low-range, and 1 to select high-range. the gpio port is confi gured as an input to select mid-range. enb can also be permanently grounded to select low- range or left unconnected to select mid-range if it will not be necessary to change the level selection. the equivalent circuit looking into the enb pin is a vari- able resistance, minimum 15k, to an approximately 1v source. the input will fl oat to mid range whenever the external driver sinks or sources less than 5a, a common worst-case characteristic of a high impedance or a weak pull-up or pull-down gpio confi gured as an input. the driving gpio must be able to sink at least 25a or source at least 50a to ensure a low or high state, respectively. (see the electrical characteristics table.) with the enb input voltage floating to mid-range, the charger is enabled but it will turn off its output following charge termination and will enter the monitor state. this ? ? figure 3a termination current tolerance versus programming resistance, low resistance range 22.533.544.555.566.57 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 r iprgm (k ), r-tol = 1% termination current threshold (ma) figure 3b termination current tolerance versus programming resistance, high resistance range 7 8 9 1011121314151617181920212223242526272829 0 5 10 15 20 25 30 35 r iprgm (k ), r-tol = 1% termination current threshold (ma)
sc820 15 applications information (continued) state is explained in the next section. mid-range can be selected either by fl oating the input (sourcing or sinking less than 5a) or by being externally forced such that v enb falls within the midrange limits specifi ed in the electrical characteristics table. while driven low (v enb < max v il ), the charger is enabled and will continue to fl oat-charge the battery following termination. if the charger is already in monitor state fol- lowing a previous termination, it will exit the monitor state and begin fl oat-charging. while enb is driven high (v enb > min v ih ), the charger is disabled and the enb input pin enters a high impedance state, suspending tri-level functionality. the specified high level input current i ih is required only until a high level is recognized by the sc820 internal logic. the tri- level float circuitry is then disabled and the enb input becomes high impedance. once forced high, the enb pin will not fl oat to mid range. to restore tri-level operation, the enb pin must fi rst be pulled down to mid or low range (at least to v enb < max v im ), then, if desired, released (by reconfi guring the gpio as an input) to select mid-range. if the enb gpio has a weak pull-down when confi gured as an input, then it is unnecessary to drive enb low to restore tri-level operation; simply confi gure the gpio as an input. when the enb selection changes from high-range to mid- or low-range, a new charge cycle begins and statb goes low. note that if a gpio with a weak pull-up input confi gura- tion is used, its pull-up current will fl ow from the gpio into the enb pin while it is fl oating to mid-range. since the gpio is driving a 1v equivalent voltage source through a resistance (looking into enb), this current is small ? possi- bly less than 1 a. nevertheless, this current is drawn from the gpio peripheral power supply and, therefore, from the battery after termination. (see the next section, monitor state.) for this reason, it is preferable that the gpio chosen to operate the enb pin should provide a true high imped- ance (cmos) configuration or a weak pull-down when configured as an input. when pulled below the float voltage, the enb pin output current is sourced from vad or vusb (the charging source), not from the battery. monitor state if the enb pin is fl oating, the charger output and statb pin will turn off and the device will enter the monitor state when a charge cycle is complete. if the battery voltage falls below the re-charge threshold (v cv - v req ) while in the monitor state, the charger will automatically initiate a re- charge cycle. the battery leakage current during monitor state is no more than 1 a over temperature and typically less than 0.1 a at room temperature. while in the monitor state, the enb tri-level input pin remains fully active, and although in midrange, is sensitive to both high and low levels. the sc820 can be forced from the monitor state (no float-charging) directly to float- charging operation by driving enb low. this operation will turn on the charger output, but will not assert the statb output. if the enb pin is again allowed to fl oat to mid- range, the charger will remain on only until the output current becomes less than the termination current, and charging terminates. the sc820 turns off its charging output and returns to the monitor state within a millisec- ond. this forced re-charge behavior is useful for periodi- cally testing the battery state-of-charge and topping-off the battery, without fl oat-charging and without requiring the battery to discharge to the automatic re-charge voltage. enb should be held low for at least 1ms to ensure a successful forced re-charge. forced re-charge can be requested at any time during the charge cycle, or even with no charging source present, with no detrimental effect on charger operation. this allows the host processor to schedule a forced re-charge at any desired interval, without regard to whether a charge cycle is already in progress, or even whether a charging source is present. forced re-charge will neither assert nor release the statb output. status output the statb pin is an open-drain output. it is asserted (driven low) as charging begins after a valid charging source is connected and the voltage on either input is between its selection and ovp limits. statb is also asserted as charging begins after the enb input returns to either of the enable voltage ranges (mid or low voltage) from the disable range. statb is subsequently released when the termination current is reached to indicate end-
sc820 16 applications information (continued) of-charge, when the enb input is driven high to disable charging, or when neither charging input is selected and valid to charge. if the battery is already fully charged when a charge cycle is initiated, statb is asserted for approximately 750s before being released. the statb pin is not asserted for automatic re-charge cycles. the statb pin may be connected to an interrupt input to notify a host controller of the charging status or it can be used as an led driver. logical cc-to-cv transition the sc820 diff ers from monolithic linear single cell li-ion chargers that implement a linear transition from cc to cv regulation. the linear transition method uses two simul- taneous feedback signals output voltage and output current to the closed-loop controller. when the output voltage is suffi ciently below the cv regulation voltage, the infl uence of the voltage feedback is negligible and the output current is regulated to the desired current. as the battery voltage approaches the cv regulation voltage (4.2v), the voltage feedback signal begins to infl uence the control loop, which causes the output current to decrease although the output voltage has not reached 4.2v. the output voltage limit dominates the controller when the battery reaches 4.2v and eventually the controller is entirely in cv regulation. the soft transition eff ectively reduces the charge current below that which is permitted for a portion of the charge cycle, which increases charge time. in the sc820, a logical transition is implemented from cc to cv to recover the charge current lost due to the soft transition. the controller regulates only current until the output voltage exceeds the transition threshold voltage. it then switches to cv regulation. the transition voltage from cc to cv regulation is typically 5mv higher than the cv regulation voltage, which provides a sharp and clean transition free of chatter between regulation modes. the diff erence between the transition voltage and the regula- tion voltage is termed the cc/cv overshoot. while in cv regulation, the output current sense remains active. if the output current exceeds by 5% the programmed fast- charge current, the controller reverts to current regulation. the logical transition from cc to cv results in the fastest possible charging cycle that is compliant with the speci- fi ed current and voltage limits of the li-ion cell. the output current is constant at the cc limit, then decreases abruptly when the output voltage steps from the overshoot voltage to the regulation voltage at the transition to cv control. thermal limiting device thermal limiting is the third output constraint of the constant current, constant voltage, constant temperature (cc/cv/ct) control. this feature permits a higher input ovp threshold, and thus the use of higher voltage or poorly regulated adapters. if high input voltage results in excessive power dissipation, the output current is reduced to prevent overheating of the sc820. the thermal limiting controller reduces the output current by i t C50ma/oc for any junction temperature t j > t tl . when thermal limiting is inactive, t j = t a + v i fq ja , where v is the voltage difference between the vin pin and the bat pin. however, if t j computed this way exceeds t tl , then thermal limiting will become active and the thermal limiting regulation junction temperature will be t jtl = t a + v i(t jtl ) ja , where i(t jtl ) = i fq + i t (t jtl ? t tl ). (note that i t is a negative quantity.) combining these two equations and solving for t jtl , the steady state junction temperature during active thermal limiting is ja t ja tl t x _ fq a jtl i v 1 t i i v t t t t ' ' although the thermal limiting controller is able to reduce output current to zero, this does not happen in practice. output current is reduced to i(t jtl ), reducing power dissi- pation such that die temperature equilibrium t jtl is reached.
sc820 17 applications information (continued) while thermal limiting is active, all charger functions remain active and the charger logical state is preserved. operating a charging adapter in current limit in high charging current applications, charger power dis- sipation can be greatly reduced by operating the charging adapter in current limit. the sc820 vad input supports adapter-current-limited charging with a low de-selection falling threshold and with internal circuitry designed for low input voltage operation. to operate an adapter in current limit, r iprgm is chosen such that the adapter input programmed fast-charge current i fq_ad exceeds the current limit of the charging adapter i ad-lim . note that if i ad-lim is less than 20% of i fq_ad , then the adapter voltage can be pulled down to the battery voltage while the battery voltage is below the pre-charge threshold. in this case, care must be taken to ensure that the adapter will maintain its current limit below 20% of i fq_ad at least until the battery voltage exceeds the pre-charge thresh- old. failure to do so could permit charge current to exceed the pre-charge current while the battery voltage is below the pre-charge threshold. this is because the low input voltage will also compress the pre-charge threshold inter- nal reference voltage to below the battery voltage. this will prematurely advance the charger logic from pre- charge current regulation to fast-charge regulation, and the charge current will exceed the safe level recom- mended for pre-charge conditioning. the low de-selection falling threshold (vt adsel-f ) permits the adapter voltage to be pulled down to just above the battery voltage by the charging load whenever the adapter current limit is less than the programmed fast- charge current. the sc820 should be operated with adapter voltage below the rising selection threshold (vt adsel-r ) only if the low input voltage is the result of adapter current limiting. this implies that the vad voltage fi rst exceeds vt adsel-r to begin charging, and is subsequently pulled down to just above the battery voltage by the charging load. interaction of thermal limiting and current limited adapter charging to permit the charge current to be limited by the adapter, it is necessary that the adapter input fast-charge current be programmed greater than the maximum adapter current, (i ad-lim ). in this confi guration, the cc regulator will operate with its pass device fully on (in saturation, also called dropout). the voltage drop from vad to bat is determined by the product of the minimum r ds-on of the pass device multiplied by the adapter supply current. in dropout, the power dissipation in the sc820 is p ilim = (minimum r ds-on ) x (i ad-lim ) 2 . since minimum r ds-on does not vary with battery voltage, dropout power dissi- pation is constant throughout the cc portion of the charge cycle while the adapter remains in current limit. the sc820 junction temperature will rise above ambient by p ilim x ja . if the device temperature rises to the tem- perature at which the tl control loop limits charging current (rather than the current being limited by the adapter), the input voltage will rise to the adapter regula- tion voltage. the power dissipation will increase so that the tl regulation will further limit charge current. this will keep the adapter in voltage regulation for the remainder of the charge cycle. in this case, the sc820 will continue to charge with thermal limiting until charge current decreases while in cv regulation (reducing power dissipa- tion suffi ciently), resulting in a slow charge cycle, but with no other negative eff ect. to ensure that the adapter remains in current limit, the internal device temperature must not rise to t tl . this implies that ja must be kept small enough, through careful layout, to ensure that t j = t a + (p ilim ja ) < t tl . vusb under-voltage load regulation vusb pin uvlr prevents the battery charging current from overloading the usb vbus network, regardless of the pro- grammed fast-charge value. when the vusb input is selected, the sc820 monitors the input voltage (v vusb ) and reduces the charge current as necessary to keep v vusb at or above the uvlr limit of v uvlr = 4.57v typically. uvlr oper- ates like a fourth output constraint (along with cc, cv, and ct constraints), but it is active only when the vusb input is selected. if the vusb voltage is externally pulled below v uvlr while the vad input is absent, the uvlr feature will reduce the charging current to zero. this condition will not be inter- preted as termination and will not result in an end-of- charge indication. the statb pin will remain asserted as if charging is continuing. this prevents repetitive indica-
sc820 18 conduction of heat from the die to the ambient environ- ment. in this experiment, the final steady-state bat current was 462ma at t a = 25c on the sc820 evaluation board. the fast thermal limiting feature ensures compli- ance with ccsa yd/t 1591-2006, telecommunication industrial standard of the peoples republic of china technical requirements and test method of charger and interface for mobile telecommunication terminal , section 4.2.3.1. short circuit protection the sc820 can tolerate a bat pin short circuit to ground indefinitely. the current into a ground short (while v bat < 1.8v) is approximately 10ma. for v bat > 1.8v, normal pre-charge current regulation is active. a short circuit or too little programming resistance to ground on the iprgm pin (<< 2.05k) or the ipusb pin (<< 4.42k) will prevent proper regulation of the bat pin output current for the active programming pin. prior to enabling the output a check of the iprgm and ipusb pins is performed to ensure that there is suffi cient resistance to ground. a test current is output on each programming pin. if the test current produces a voltage of suffi cient amplitude on both programming pins, regardless of input selected, then the output is enabled. an example with r iprgm = 2.94k is illustrated in figure 5, in which the test current is applied for approximately 250s to determine that there is no pin short. if a short on either program- ming pin is detected, the test current persists until the short to ground is removed, and then the charging startup sequence will continue. 400s/div figure 5 iprgm pin short-to-ground test during startup tions of end-of-charge alternating with start-of-charge in the case that the external vusb load is removed or is intermittent. input over-voltage protection the vad and vusb input pins are protected from over- voltage to at least 30v above gnd. when the voltage of the selected input exceeds the over-voltage protection (ovp) rising threshold (vt ovp-r ), charging is halted. when the input voltage falls below the ovp falling threshold (vt ovp-f ), charging resumes. note that the vad input remains selected even in the case that the vad voltage exceeds the ovp threshold. an excessive vad voltage will disable charging despite the presence of a valid vusb voltage. an ovp fault turns off the statb output. statb is turned on again when charging restarts. the ovp threshold has been set relatively high to permit the use of poorly regulated adapters. such adapters may output a high voltage until loaded by the charger. a too-low ovp threshold could prevent the charger from ever turning on and loading the adapter to a lower voltage. if the adapter voltage remains high despite the charging load, the fast thermal limiting feature will immediately reduce the charging current to prevent overheating of the sc820. this behavior is illustrated in figure 4, in which v bat = 3.0v, i fq = 700ma, and v vad is stepped from 0v to 8.1v. initially, power dissipation in the sc820 is 3.6w. 1s/div v vad (2v/div) v vad ,v bat =0v i bat (100ma/div) i bat =0ma v vad =8.1v, v bat =3.0v i bat =700ma (initially), p dissipation =3.6w (initially) v bat (2v/div) figure 4 thermal limiting example notice the bat output current is rapidly reduced to limit the internal die temperature, then continues to decline as the circuit board gradually heats up, further reducing the applications information (continued) i bat (500ma/div) i bat =0ma v iprgm =0v v vin (5v/div) v iprgm (1v/div) v vin =0v
sc820 19 during charging, a short to ground applied to the selected- input active current programming pin (iprgm or ipusb) is detected by a different mechanism, while a short to ground on the inactive programming pin is ignored. pin- short detection on an active current programming pin forces the sc820 into reset, turning off the output. a pin- short on either programming pin will then prevent startup regardless of the input selected. when the iprgm and ipusb pin-short conditions are removed, the charger begins normal operation automatically without input power cycling. over-current protection over-current protection is provided in all modes of opera- tion, including cv regulation. the output current is limited to either the pre-charge or the fast-charge current (as programmed by iprgm or ipusb, determined by input selection), depending on the voltage at the output. operation without a battery the sc820 can be operated as a 4.2v ldo regulator without the battery present, for example, for factory testing. if this use is anticipated, the total output capaci- tance, c bat plus any other capacitors tied directly to bat pin network, should be at least 2.2f but less than 22f to ensure stability in cv regulation. to operate the charger without a battery, the enb pin must be driven low or grounded. the output current is limited by the pro- grammed fast-charge current for the selected input. the charger should not be disabled (v enb > v ih ) without a battery present. design considerations usb charging the usb specifi cation restricts the load on the usb vbus power network to 100ma for low power devices and for high power devices prior to granting permission for high power operation. the specifi cation restricts the vbus load to 500ma for high power devices after granting permis- sion to operate as a high power device. this suggests that a fixed 1:5 ratio of low power to high power charging current is desirable. but this can result in suboptimal charging when the battery capacity is too small to permit fast charging at 500ma. for example, a 250mah battery will typically require a fast-charge current of 250ma or less. a fi xed 1:5 ratio for usb low and high power charging will unnecessarily reduce charging current to 50ma, well below the 100ma permitted. an arbitrary ratio of usb low-to-high power charging cur- rents can be obtained using an external n-channel fet operated with a processor gpio signal to engage a second parallel ipusb resistor. the external circuit is illustrated in figure 6. ipusb 5 r ipusb r ipusb_hi usb hi/lo power select figure 6 external programming of arbitrary usb high power and low power charge currents. for usb low power mode charging, the external transistor is turned off . the transistor is turned on when high power mode is desired. the eff ect of the switched parallel ipusb resistor is to reduce the eff ective programming resistance and thus raise the fast-charge current. an open-drain gpio can be used directly to engage the parallel resistor r ipusb_hi . care must be taken to ensure that the r ds-on of the gpio is considered in the selection of r ipusb_hi . also important is the part-to-part and tempera- ture variation of the gpio r ds-on , and their contribution to the usb high power charge current tolerance. note also that ipusb will be pulled up briefl y to as high as 3v during startup to check for an ipusb static pinshort to ground. a small amount of current could, potentially, flow from ipusb into the gpio esd structure through r ipusb_hi during this event. while unlikely to do any harm, this eff ect must also be considered. for purposes of design for dual-input adapter/usb charg- ing, a small battery is one with a desired fast-charge current less than 500ma. a 300mah battery with maximum fast-charge current of 300ma is an example. the adapter input and usb input high power fast-charge currents should both be set to 300ma maximum. the usb input low power fast-charge current is 100ma maximum. refer to the circuit of figure 4 and the data of figures 1a and 1b. for i fq_ad = 300ma maximum, use r iprgm = 7.50k. the fi xed ipusb resistor of r ipusb = 23.2k programs i fq_usb applications information (continued)
sc820 20 = 100ma maximum. when parallel resistor r ipusb_hi = 11.0k is switched in, the equivalent ipusb resistor is 7.50k, and so i fq_usb = 300ma maximum. a large battery is any battery with a desired fast-charge current exceeding 500ma. large battery charging is most consistent with the usb fi xed 1:5 current ratio low-to-high power model of operation. for example, consider an 800mah battery, with maximum fast-charge current of 800ma. the adapter input fast-charge should be confi g- ured for 800ma maximum (r iprgm = 2.80k), the usb low power fast-charge set to 100ma max (r ipusb = 23.2k), and the usb high power fast-charge set to 500ma maximum (r ipusb_hi = 5.62k). usb low power mode alternative where a usb mode selection signal is not available, or where system cost or board space make usb low power mode external current programming impractical, usb low power charging can be supported indirectly. the ipusb pin resistance can be selected to obtain the desired usb high power charge current. the vusb pin uvlr feature ensures that the charging load will never pull the usb vbus supply voltage below v uvlr regardless of the usb host or hub supply limit. the uvlr limit voltage guaran- tees that the voltage of the usb vbus supply will not be loaded below the low power voltage specifi cation limit, as seen by any other low power devices connected to the same usb host or hub. capacitor selection low cost, low esr ceramic capacitors such as the x5r and x7r dielectric material types are recommended. the bat pin capacitor should be at least 1f, but can be as large as desired to accommodate the required input capacitors of regulators connected directly to the battery terminal. bat pin total capacitance must be limited if the sc820 is to be operated without the battery present. see the section operation without a battery. the vad pin and vusb pin capacitors are typically between 0.1f and 2.2f, although larger values will not degrade performance. capacitance must be evaluated at the expected bias voltage (4.2v for the bat pin capacitor, the expected v vad and v vusb supply regulation voltages for the input pin capacitors), rather than the zero-volt capacitance rating. pcb layout considerations layout for linear devices is not as critical as for a switching regulator. however, careful attention to detail will ensure reliable operation. place input and output capacitors close to the device for optimal transient response and device behavior. connect all ground connections directly to the ground plane. if there is no ground plane, connect to a common local ground point before connecting to board ground near the gnd pin. attaching the part to a larger copper footprint will enable better heat transfer from the device, especially on pcbs with internal ground and power planes. ? ? ? applications information (continued)
sc820 21 2.00 .079 pin 1 indicator (laser mark) a1 seating plane c b a aaa c 1 n e 2.10 2.10 1.90 1.90 .083 .083 .075 .075 2 a2 d e/2 e bxn bbb c a b coplanarity applies to the exposed pad as well as the terminals. 2. d1 .061 .067 .071 1.55 1.70 1.80 e1 .026 .031 .035 0.65 0.80 0.90 d/2 e/2 e lxn d1 e1 inches .020 bsc b .007 bbb aaa n l e d .012 dim a1 a2 a min .000 .020 0.30 0.18 .012 0.25 .010 0.40 0.30 .004 .003 8 .014 .079 .016 0.08 0.10 8 0.35 2.00 0.50 bsc millimeters max 0.05 0.60 dimensions min 0.00 nom (.006) - - max .002 .024 nom 0.50 - (0.1524) - controlling dimensions are in millimeters (angles in degrees). notes: 1. a outline drawing mlpd-ut8 2x2
semtech corporation power management products division 200 flynn road, camarillo, ca 93012 phone: (805) 498-2111 fax: (805) 498-3804 www.semtech.com contact information sc820 22 land pattern mlpd-ut8 2x2 inches dimensions p z x y c g dim millimeters failure to do so may compromise the thermal and/or functional performance of the device. shall be connected to a system ground plane. thermal vias in the land pattern of the exposed pad 3. h .067 1.70 k .031 0.80 r .006 0.15 y r g z p x (c) 1. controlling dimensions are in millimeters (angles in degrees). h k .030 .106 (.077) .047 0.75 2.70 (1.95) 1.20 0.30 0.50 .020 .012 this land pattern is for reference purposes only. consult your manufacturing group to ensure your company's manufacturing guidelines are met. notes: 2.

▲Up To Search▲

Price & Availability of SC820-1

	To Download SC820-1 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .