SC811 / SC813 Adapter/USB Tri-Mode Single-cell Li-ion Charger POWER MANAGEMENT Features Description The SC811 and SC813 are highly versatile single input triple mode (adapter/USB high current, USB low current) linear single-cell Li-ion battery chargers, each in an 8 lead 2x2 MLPD ultra-thin package. The input will survive sustained input voltage up to 30V to protect against hot plug overshoot and faulty charging adapters. The SC811 has 9.6V rising, 8.2V falling OVP thresholds for general purpose charging with low cost adaptors. The SC813 has 6V rising, 5.6V falling OVP thresholds for customers utilizing charging adapters with specifications that are similar to a USB Vbus supply. The SC811 and SC813 differ only in OVP threshold. Single input charger with three charging modes Constant voltage — 4.2V, 1% regulation Fast-charge current regulation — 15% at 70mA, 9% at 700mA Charging by current regulation, voltage regulation, and thermal limiting Input voltage protection — 30V Current-limited adapter support capability — reduces power dissipation in charger IC USB high and low power modes limit charge current to prevent USB Vbus overload Instantaneous CC-to-CV transition for faster charging Programmable battery-dependent currents (adapter mode fast- and pre-charge, termination) Programmable source-limited currents (USB-high mode fast-charge, and USB-low mode fast- and pre-charge) Independent programming of termination current with dual-mode operation Three termination options — float-charge, automatic re-charge, or forced re-charge to keep the battery topped-off after termination without float-charging Soft-start reduces adapter or USB load transients High operating voltage range of SC811 permits use of unregulated adapters Complies with CCSA YD/T 1591-2006 Space saving 2x2x0.6 (mm) MLPD package WEEE and RoHS compliant Applications Mobile phones MP3 players GPS handheld receivers Typical Application Circuit Charging begins automatically when an input source is applied to the charging input. Thermal limiting protects against excessive power dissipation. The charger can be programmed to turn off when charging is complete or to continue operating as an LDO regulator while float-charging the battery. Three charging modes are provided: adapter mode, USB low power mode, and USB high power mode. Batterycapacity-dependent and charging source-dependent current programming are independently programmed. Adapter and USB high power modes can charge up to 1A, with the charging adapter operating either in voltage regulation or in current limit to obtain the lowest possible power dissipation. A single current programming pin is used to program pre-charge, termination, and adaptermode fast-charge currents in fixed proportions. In the USB modes, a second programming pin is used to program low power pre-charge current and low and high power fast-charge currents. This configuration allows independent programming of termination current. The two USB modes dynamically limit the charging load if necessary to prevent overloading the USB Vbus supply. SC811 / SC813 VADAPTER VIN ENB MODE SELECT MODE BAT STATB IPRGM GND IPUSB 2.2 μF April 7, 2008 © 2008 Semtech Corporation Battery Pack Device Load 2.2 μF 1 SC811 / SC813 Pin Configuration VIN Ordering Information 1 8 ENB TOP VIEW MODE 2 7 BAT STATB 3 6 IPRGM GND 4 5 IPUSB Device Package SC811ULTRT(1)(2) MLPD-UT-8 2×2 SC813ULTRT(1)(2) MLPD-UT-8 2×2 SC811EVB Evaluation Board SC813EVB Evaluation Board Notes: (1) Available in tape and reel only. A reel contains 3,000 devices. (2) Lead-free package only. Device is WEEE and RoHS compliant. T MLPD-UT8; 2x2, 8 LEAD θJA = 68°C/W Marking Information 81x yw x = 1 or 3 yw = Date Code © 2008 Semtech Corporation 2 SC811 / SC813 Absolute Maximum Ratings Recommended Operating Conditions VIN (V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to +30.0 Operating Ambient Temperature (°C) . . . . . . . . . -40 to +85 BAT, IPRGM, IPUSB (V) . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to +6.5 SC811: STATB, ENB, MODE (V) . . . . . . . . . . . . . . . . . . . -0.3 to VBAT + 0.3 VIN Adapter Mode Operating Voltage(2) (V) . . . 4.60 to 8.20 VIN Input Current (A) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 VIN USB Modes Operating Voltage(2) (V) . . . . . . 4.35 to 8.20 Total Power Dissipation (W) . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 SC813: BAT, IPRGM, IPUSB Short to GND Duration . . . . Continuous VIN Adapter Mode Operating Voltage(2) (V) . . . 4.60 to 5.60 ESD Protection Level(1) (kV) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 VIN USB Modes Operating Voltage(2) (V) . . . . . . 4.35 to 5.60 Thermal Information Thermal Resistance, Junction to Ambient(3) (°C/W) . . . . . 68 Junction Temperature Range (°C) . . . . . . . . . . . . . . . . . . +150 Storage Temperature Range (°C) . . . . . . . . . . . . -65 to +150 Peak IR Reflow Temperature (°C) . . . . . . . . . . . . . . . . . . . +260 Exceeding the above specifications may result in permanent damage to the device or device malfunction. Operation outside of the parameters specified in the Electrical Characteristics section is not recommended. NOTES: (1) Tested according to JEDEC standard JESD22-A114-B. (2) This is the input voltage at which the charger is guaranteed to begin operation. Maximum operating voltage is the maximum Vsupply as defined 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. Electrical Characteristics Test Conditions: VVIN = 4.75V to 5.25V; VBAT = 3.7V; Typ values at 25°C; Min and Max at -40°C < TA < 85°C, unless specified. Parameter Symbol VIN Adapter Mode Rising Threshold VTADUVLO-R VIN Adapter Mode Falling Threshold (1) VTADUVLO-F VVIN > VBAT VIN USB Modes Rising Threshold VTUSBUVLO-R VVIN > VBAT VIN USB Modes Falling Threshold VTUSBUVLO-F VVIN > VBAT 3.65 VIN USB Modes Hysteresis VTUSBUVLO-H VTUSBUVLOR - VTUSBUVLOF 100 VIN OVP Rising Threshold VTOVP-R VIN OVP Falling Threshold VIN OVP Hysteresis Conditions Min Typ Max Units 4.30 4.45 4.60 V 2.70 2.85 3.00 V 4.20 4.35 V 4.00 V mV All modes, SC811 9.0 9.6 All modes, SC813 5.85 6.0 V All modes, SC811 8.2 8.8 All modes, SC813 5.6 5.75 VTOVP-R - VTOVP-F , all modes, SC811 50 200 VTOVP-R - VTOVP-F , all modes, SC813 50 100 VTOVP-F V VTOVP-H mV © 2008 Semtech Corporation 3 SC811 / SC813 Electrical Characteristics (continued) Parameter Symbol Conditions VIN Charging Disabled Quiescent Current IqVIN_DIS VIN Charging Enabled Quiescent Current CV Regulation Voltage CV Voltage Load Regulation Typ Max Units VENB = VBAT 2 3 mA IqVIN_EN VENB = 0V, excluding IBAT, IIPRGM, and IIPUSB 2 3 mA VCV IBAT = 50mA, -40°C ≤ TJ ≤ 125°C 4.20 4.24 V 10 mV VCV_LOAD Re-charge Threshold VTReQ Pre-charge Threshold (rising) VTPreQ Battery Leakage Current Relative to VCV @ 50mA, 1mA ≤ IBAT ≤ 1A, -40°C ≤ TJ ≤ 125°C VCV - VBAT Min 4.16 -20 60 100 140 mV 2.85 2.90 2.95 V lBAT_V0 VBAT = VCV, VVIN = 0V 0.1 1 μA lBAT_DIS VBAT = VCV, VVIN = 5V, VENB = 2V 0.1 1 μA lBAT_MON VBAT = VCV, VVIN = 5V; ENB not connected 0.1 1 μA 29.4 kΩ IPRGM Programming Resistor RIPRGM Fast-Charge Current, Adapter Mode IFQ_AD RIPRGM = 2.94kΩ, VTPreQ < VBAT < VCV 643 694 745 mA Pre-Charge Current, Adapter Mode and USB High Power Mode IPreQ_AD RIPRGM = 2.94kΩ, 1.8V < VBAT < VTPreQ 105 139 173 mA Termination Current, Any Mode ITERM RIPRGM = 2.94kΩ, VBAT = VCV 59 69 80 mA IPUSB Programming Resistor RIPUSB 29.4 kΩ Fast-Charge Current, USB High Power Mode IFQ_USB RIPUSB = 4.42kΩ, 1.8V < VBAT < VTPreQ 427 462 497 mA Pre-Charge Current and Fast-Charge Current, USB Low Power Mode IPreQ_USB RIPUSB = 4.42kΩ, 1.8V < VBAT < VCV 69 92 116 mA VDO IBAT = 700mA, 0°C ≤ TJ ≤ 125°C 0.40 0.60 V IPRGM Fast-charge Regulated Voltage VIPRGM_FQ VVIN = 5.0V, VTPreQ < VBAT < VCV 2.04 V IPRGM Pre-charge Regulated Voltage VIPRGM_PQ 1.8V < VBAT < VTPreQ 0.408 V IPRGM Termination Threshold Voltage VTIPRGM_TERM VBAT = VCV (either input selected) 0.204 V IPUSB Fast-charge Regulated Voltage VIPUSB_FQ VVIN = 0V, VTPreQ < VBAT < VCV 2.04 V IPUSB Pre-charge or USB Low Power Mode Regulated Voltage VIPUSB_PQ VVIN = 0V, VBAT < VTPreQ 0.408 V VIN USB Modes Under-Voltage Load Regulation Limiting Voltage VUVLR 5mA ≤ VIN supply current limit ≤ 500mA, VMODE = 2V, RIPUSB = 3.65kΩ (559mA) Dropout Voltage 2.05 2.05 © 2008 Semtech Corporation 4.45 4.58 4.70 V 4 SC811 / SC813 Electrical Characteristics (continued) Parameter Symbol Conditions Min Typ Max Units Thermal Limiting Threshold Temperature T TL 130 °C Thermal Limiting Rate iT 50 mA/ °C ENB or MODE Input High Voltage Threshold VIH 1.6 ENB or MODE Input Mid Voltage Range VIM 0.7 ENB or MODE Input Low Voltage Threshold VIL V 1.3 V 0.3 V ENB Input High-range Threshold Input Current IENB_IH_TH ENB current required to pull ENB from floating midrange into high range 23 50 μA ENB Input High-range Sustain Input Current IENB_IH_SUS Current required to hold ENB in high range, Min VIH ≤ VENB ≤ VBAT, Min VIH ≤ VBAT ≤ 4.2V 0.3 1 μA IMODE_IH VMODE = Min VIH 23 75 μA ENB or MODE Input Mid-range Load Limit IIM Input will float to mid range when this load limit is observed. -5 5 μA ENB or MODE Input Low-range Input Current IIL 0V ≤ (VENB or VMODE) ≤ Max VIL -25 IMODE_MON VMODE = VBAT = 4.2V, VENB = 1V and Charging Terminated 1 μA IILEAK VVIN = 0V or VVIN = 5V, VENB and VMODE = VBAT = 4.2V 1 μA STATB Output Low Voltage VSTAT_LO ISTAT_SINK = 2mA 0.5 V STATB Output High Current ISTAT_HI VSTAT = 5V 1 μA MODE Input High-range Input Current MODE Input Monitor State Input Current ENB or MODE Input Leakage 12 μA Notes: (1) Sustained operation to VTADUVLO-F ≤ VVIN is guaranteed only if a current limited charging source applied to VIN is pulled below VTADUVLO-R by the charging load; forced VIN voltage below VTADUVLO-R may in some cases result in regulation errors or other unexpected behavior. © 2008 Semtech Corporation 5 SC811 / SC813 Typical Characteristics CV Line Regulation CV Load Regulation ο ο TA = 25 C, VVIN = 5V 4.204 4.204 4.2 4.2 4.196 4.196 VBAT (V) VBAT (V) TA = 25 C, IBAT = 50mA 4.192 4.192 4.188 4.188 4.184 4.184 4.18 5 5.5 6 6.5 7 7.5 4.18 0 8 100 200 300 400 500 600 700 800 IBAT (mA) VVIN (V) CV Temperature Regulation CC AD or USB High FQ Line Regulation ο VVIN = 5V, IBAT = 50mA TA = 25 C, VBAT = 3.7V 4.204 720 4.2 680 RIPRGM or RIPUSB = 2.94kΩ 640 IBAT (mA) VBAT (V) 4.196 4.192 600 560 4.188 520 4.184 4.18 RIPRGM or RIPUSB = 4.42kΩ 480 -40 -20 0 20 40 60 80 100 440 4.5 120 5 5.5 6 o CC AD or USB High FQ VBAT Regulation 7.5 8 VVIN = 5V, VBAT = 3.7V 720 720 680 680 RIPRGM or RIPUSB = 2.94kΩ RIPRGM or RIPUSB = 2.94kΩ 640 IBAT (mA) 640 IBAT (mA) 7 CC AD or USB High FQ Temperature Regulation ο TA = 25 C, VVIN = 5V 600 560 520 600 560 520 RIPRGM or RIPUSB = 4.42kΩ 480 440 2.9 6.5 VVIN (V) Ambient Temperature ( C) 3.1 3.3 3.5 3.7 RIPRGM or RIPUSB = 4.42kΩ 480 3.9 4.1 440 -40 -20 0 20 40 60 80 100 120 o VBAT (V) Ambient Temperature ( C) © 2008 Semtech Corporation 6 SC811 / SC813 Typical Characteristics CC PQ Line Regulation CC PQ Temperature Regulation ο VVIN = 5V, VBAT = 2.6V TA = 25 C, VBAT = 2.6V 160 160 150 150 RIPRGM or RIPUSB = 2.94kΩ IBAT (mA) IBAT (mA) 130 120 110 130 120 110 RIPRGM or RIPUSB = 4.42kΩ RIPRGM or RIPUSB = 4.42kΩ 100 100 90 RIPRGM or RIPUSB = 2.94kΩ 140 140 5 5.5 6 6.5 7 7.5 90 8 -40 -20 20 40 60 80 100 120 Ambient Temperature ( C) CC USB Low Power FQ Line Regulation CC USB Low Power FQ VBAT Regulation ο ο TA = 25 C, VVIN = 5V TA = 25 C, VBAT = 3.7V 160 160 150 150 RIPUSB = 2.94kΩ RIPUSB = 2.94kΩ 140 IBAT (mA) 140 IBAT (mA) 0 o VVIN (V) 130 120 110 130 120 110 RIPUSB = 4.42kΩ RIPUSB = 4.42kΩ 100 100 90 4.5 5 5.5 6 6.5 7 7.5 8 90 2.9 3.1 3.3 3.5 3.7 3.9 4.1 VBAT (V) VVIN (V) CC USB Low Power FQ Temperature Regulation VVIN = 5V, VBAT = 3.7V 160 150 RIPUSB = 2.94kΩ IBAT (mA) 140 130 120 110 RIPUSB = 4.42kΩ 100 90 -40 -20 0 20 40 60 80 100 120 o Ambient Temperature ( C) © 2008 Semtech Corporation 7 SC811 / SC813 Typical Characteristics IFQ_AD vs. RIPRGM , or IFQ_USB High Power vs. RIPUSB IPQ_AD or IPQ_USB vs. RIPRGM, or IFQ_USB Low Power vs. RIPUSB ο ο VVIN = 5V, VBAT = 2.6V, TA = 25 C 1000 200 800 160 IBAT (mA) 600 120 400 80 200 40 6 10 14 18 22 26 0 2 30 6 10 14 18 22 26 30 RIPRGM or RIPUSB (kΩ) RIPRGM or RIPUSB (kΩ) Charging Cycle Battery Voltage and Current Pre-Charging Battery Voltage and Current ο ο 850mAhr battery, RIPRGM = 2.94kΩ, VVIN = 5.0V, TA = 25 C 850mAhr battery, RIPRGM = 2.94kΩ, VVIN = 5.0V, TA = 25 C 800 7 700 6 600 5 500 700 3.75 400 300 3 IBAT 2 1 0 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 3.5 600 3.25 500 VBAT (V) VBAT 4 IBAT IBAT (mA) VBAT (V), Internal Power Dissipation (W) 4 400 3 VBAT 2.75 300 200 2.5 200 100 2.25 100 2 0 0 2.25 2 4 6 CC-to-CV Battery Voltage and Current 670 4.19 650 4.18 VBAT 630 4.17 46 46.5 47 47.5 610 48 IBAT (mA) VBAT (V) 690 45.5 16 18 0 20 450 4.5 VBAT (V), Internal Power Dissipation (W) IBAT 45 14 850mAhr battery, RIPRGM = 2.94kΩ, VVIN = 5.0V, Load = 10mA 710 4.21 44.5 12 Re-Charge Cycle Battery Voltage and Current ο 850mAhr battery, RIPRGM = 2.94kΩ, VVIN = 5.0V, TA = 25 C 4.16 44 10 Time (s) Time (hrs) 4.2 8 IBAT (mA) 0 2 4 400 VBAT 3.5 350 3 300 2.5 250 2 200 IBAT (mA) IBAT (mA) VVIN = 5V, VBAT = 3.7V, TA = 25 C 150 1.5 IBAT 1 100 50 0.5 Discharge hours 2 - 6 omitted. 0 0.0 Time (min) 0.5 1.0 1.5 2/6 6.5 7.0 0 7.5 Time (hrs) © 2008 Semtech Corporation 8 SC811 / SC813 Typical Characteristics Mode Reselection — USB Low to USB High Mode Reselection — USB High to USB Low VVIN=5V, VBAT=3.7V VVIN=5V, VBAT=3.7V IBAT (100mA/div)) VMODE (2V/div) VMODE (2V/div) VMODE=0V— VMODE=0V— IBAT (100mA/div) IBAT=0mA— IBAT=0mA— 100μs/div Mode Reselection — AD to USB High 100μs/div Mode Reselection — USB High to AD VVIN=5V, VBAT=3.7V VVIN=5V, VBAT=3.7V IBAT (100mA/div) IBAT (100mA/div) VMODE (2V/div) VMODE (2V/div) VMODE=0V— VMODE=0V— IBAT=0mA— IBAT=0mA— 100μs/div 100μs/div Mode Reselection — USB Low to AD Mode Reselection — AD to USB Low VVIN=5V, VBAT=3.7V VVIN=5V, VBAT=3.7V IBAT (100mA/div) VMODE (2V/div) VMODE (2V/div) VMODE=0V— VMODE=0V— IBAT (100mA/div) IBAT=0mA— 100μs/div IBAT=0mA— © 2008 Semtech Corporation 100μs/div 9 SC811 / SC813 Pin Descriptions Pin # Pin Name 1 VIN Supply pin — connect to charging adapter (wall adapter or USB). This pin is protected against damage due to high voltage up to 30V. 2 MODE Charging mode selection (tri-level logical) input — Logical high selects USB high power mode, floating selects USB low power mode, ground selects adapter mode. 3 STATB Status output pin — This open-drain pin is asserted (pulled low) when a valid charging supply is connected to the VIN pin, 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 IPUSB Fast-charge and pre-charge current programming pin for a USB mode charging source — USB high power mode (100%) and low power mode (20%) fast-charge current are programmed by connecting a resistor from this pin to ground. USB low power mode pre-charge current is equal to the low power mode fast-charge current (20% of USB high power mode fast-charge current). 5 Pin Function Adapter mode fast-charge, adapter and USB high power modes pre-charge, and all modes termination current programming pin — Connect a resistor from this pin to ground. Pre-charge current is 20% of IPRGM-programmed adapter mode fast-charge current when in adapter mode or USB high power mode. The charging termination current threshold (for adapter or either USB mode selection) is 10% of the IPRGM programmed fast-charge current. 6 IPRGM 7 BAT 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 indefinite float-charging. Float this pin to enable charging without float-charge upon termination. Note that this pin must be grounded if the SC811/3 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 multiple vias. © 2008 Semtech Corporation 10 SC811 / SC813 Block Diagram 2 V_Adapter or V_USB MODE 1 VIN 1V VTMODE_HIGH = ~1.50V Tri-level Control VTMODE_LOW = ~0.55 Mode Selection Logic Ad/USB select (USB only) Regulated System Supply VVUSB_UV_LIM = 4.575V Connect to BAT or to regulated supply VCV = 4.2V To System Load CV BAT 7 CC VIREF CC Feedback Selection Die Temperature Thermal Limiting VT_CT 3 Precharg, CC/CV & Termination Controller, Logical State Machine STATB LithiumIon Single Cell Battery Pack Termination VTIPRGM_TERM VTENB_HIGH = ~1.50V 1V Tri-level Control VTENB_LOW = ~0.55 ENB IPUSB 8 IPRGM 5 RIPUSB © 2008 Semtech Corporation GND 6 4 RIPRGM 11 SC811 / SC813 Applications Information Charger Operation The SC811/3 is a single input tri-mode stand-alone Li-ion battery charger. (The SC811 differs from the SC813 only in the input voltage Over Voltage Protection threshold.) It provides selections of adapter mode and USB high and low power mode charging. The device is independently programmed 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 specification, are programmed using the IPUSB pin when either of the USB modes is selected. When an input supply is first 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 IPRGM (adapter or USB high power modes) or IPUSB (USB low power mode) programmed fast-charge current. When the battery voltage exceeds the pre-charge threshold, 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 programmed fast-charge current) to reduce adapter load transients. CC current is programmed by the IPRGM resistance to ground when adapter mode is selected and by the IPUSB resistance to ground when either USB mode is selected. In USB low power mode, the CC current is held at 20% of the IPUSB programmed fast-charge current. The charger begins Constant Voltage (CV) regulation when the battery voltage rises to the fully-charged singlecell Li-ion regulation voltage (VCV ), 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 IBAT drops below the termination threshold current, which is 10% of the IPRGM pin programmed fast-charge current regardless of the mode selected. This is known as charge termination. Optional Float-charging or Monitoring Depending on the state of the ENB input, upon termination the SC811/3 either operates indefinitely as a voltage regulator (known as float-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 recharge threshold (VTReQ). A re-charge cycle then begins automatically and the process repeats. A forced recharge cycle can also be periodically commanded by the processor to keep the battery topped-off without floatcharging. See the Monitor State section for details. Re-charge cycles are not indicated by the STATB pin. Charging Input Pin Mode Dependencies The UVLO rising and falling thresholds are adjusted with the charging mode selected. In adapter mode, if the charging current loads the adapter beyond its current limit, the input voltage will be pulled down to just above the battery voltage. The adapter mode UVLO falling threshold is set close to the battery voltage pre-charge threshold to permit low-dissipation charging from a current limited adapter. The USB modes provide a higher UVLO falling threshold applicable to the USB specification. The USB modes also provide 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. This can be beneficial for charging small batteries, for which the USB high power fast-charge current must be programmed to less than 500mA. The fixed 20% USB low power mode fast-charge current would be less than 100mA and, therefore, is unsuitable for minimum charge-time applications. UVLR can also be used where there is no signal available to indicate whether USB low or high power mode should be selected. All modes use the same input Over-Voltage Protection (OVP) threshold as defined in the Electrical Characteristics section for the device being used. Constant Current Mode Fast-charge Current Programming Constant Current (CC) regulation is active when the battery voltage is above VTPreQ and less than VCV. When adapter mode is selected, the programmed CC regulation fast-charge (FQ) current is inversely proportional to © 2008 Semtech Corporation 12 SC811 / SC813 Applications Information (continued) the resistance between IPRGM and GND according to the equation ,)4 B $' 9,35*0 B 7\S 5,35*0 When either of the USB modes is selected, the programmed CC regulation fast-charge current is inversely proportional to the resistance between IPUSB and GND according to the equation ,)4 B 86% 9,386% B 7\S 5,386% The fast-charge current can be programmed for a minimum of 70mA and a maximum of 995mA for either adapter or USB high power mode. This range for both modes permits the use of USB high power mode for general purpose adapter charging, allowing fully independent programming of termination current. (See the application sections, Independent Programming of Termination Current, and USB-only Charging of Very Large Batteries.) Current regulation accuracy is dominated by gain error at high current settings, and offset error at low current settings. The range of expected fast-charge output current versus programming resistance RIPRGM or RIPUSB (for adapter or USB high power mode, respectively) is shown in Figures 1a and 1b. Each figure shows the nominal fast-charge current versus nominal RIPRGM or RIPUSB resistance as the center plot, and two theoretical 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 1% tolerance resistors. The dots on each plot indicate the currents obtained with standard value 1% tolerance resistors. Figures 1a and 1b show low and high resistance ranges, respectively. The USB low power mode fast-charge current accuracy is exactly like that of pre-charge in high power mode. USB low power mode current regulation accuracy is addressed in the next section. Pre-charge and USB Low Power Mode Fastcharge Current Regulation Pre-charging is automatically selected when the battery voltage is below the pre-charge threshold voltage (VTPreQ), typically 2.8V. Pre-charge current conditions the battery for fast charging. The pre-charge current value is fixed at 20% nominally of the fast-charge current. It is programmed by the resistance between IPRGM and GND for adapter mode and USB high power mode, and by the resistance between IPUSB and GND for USB low power mode. Note that USB low power mode pre-charge current is equal to USB low power mode fast-charge current. 1100 325 1050 300 1000 950 275 250 850 Fast-charge Current (mA) Fast-charge Current (mA) 900 800 750 700 650 600 550 500 225 200 175 150 125 450 400 100 350 75 300 250 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 50 7 8 9 RIPRGM or RIPUSB (kΩ), R-tol = 1% 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 RIPRGM or RIPUSB (kΩ), R-tol = 1% Figure 1a — Fast-charge Current Tolerance versus Programming Resistance, Low Resistance Range Figure 1b — Fast-charge Current Tolerance versus Programming Resistance, High Resistance Range © 2008 Semtech Corporation 13 SC811 / SC813 Applications Information (continued) 270 260 80 75 70 230 220 65 210 60 200 190 55 Pre-charge Current (mA) Pre-charge Current (mA) 250 240 180 170 160 150 140 130 120 110 100 50 45 40 35 30 25 90 20 80 70 15 10 60 50 5 40 30 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 0 7 8 9 RIPRGM or RIPUSB (kΩ), R-tol = 1% 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 RIPRGM or RIPUSB (kΩ), R-tol = 1% Figure 2a — Pre-charge Current and USB Low Power Mode Fast-charge Current Tolerance vs. Programming Resistance, Low Resistance Range Figure 2b — Pre-charge Current and USB Low Power Mode Fast-charge Current Tolerance vs. Programming Resistance, High Resistance Range Pre-charge current regulation accuracy is dominated by offset error. The range of expected pre-charge output current versus programming resistance RIPRGM or RIPUSB is shown in Figures 2a and 2b. Each figure shows the nominal pre-charge current versus nominal RIPRGM or RIPUSB resistance as the center plot and two theoretical 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 1% tolerance resistors. The dots on each plot indicate the currents obtained with standard value 1% tolerance resistors. Figures 2a and 2b show low and high resistance ranges, respectively. The termination threshold current is fixed at 10% of the adapter mode fast-charge current, as programmed by the resistance between IPRGM and GND, for all charging modes. If only the USB modes will be used, the termination threshold current can be programmed independently of the fast-charge current. (See the application sections, Independent Programming of Termination Current, and USB-only Charging of Very Large Batteries.) Termination When the battery voltage reaches VCV, the SC811/3 transitions from constant current regulation to constant voltage regulation. While VBAT is regulated to VCV, 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 floatcharges the battery, depending on the logical state of the ENB input pin. 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 within the immediate 300μs to 550μs 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 offset error. The range of expected termination current versus programming resistance RIPRGM (for any charging mode) is shown in Figures 3a and 3b. Each figure shows © 2008 Semtech Corporation 14 SC811 / SC813 Applications Information (continued) 115 35 110 105 30 95 Termination Current Threshold (mA) Termination Current Threshold (mA) 100 90 85 80 75 70 65 60 55 50 45 25 20 15 10 40 35 5 30 25 20 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 0 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 RIPRGM (kΩ), R-tol = 1% RIPRGM (kΩ), R-tol = 1% Figure 3a — Termination Current Tolerance vs. Programming Resistance, Low Resistance Range the nominal termination current versus nominal RIPRGM resistance as the center plot and two theoretical limit plots indicating maximum and minimum current vs. 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 standard value 1% tolerance resistors. Figures 3a and 3b show low and high resistance ranges, respectively. Tri-level Logical Input Pins The MODE and ENB pins are tri-level logical inputs. They are designed to interface to a processor GPIO port that is powered from a peripheral supply voltage as low as 1.8V or as high as a fully charged battery. While a connected GPIO port is configured as an output, the processor writes 0 to select ENB or MODE low-range, and 1 to select highrange. The GPIO port is configured as an input to select mid-range. These pins can also be permanently grounded to select low-range or left unconnected to select mid-range for fixed mode operation. The MODE pin can also be permanently connected to a logical high voltage source, such as BAT or a regulated peripheral supply voltage. The equivalent circuit looking into these pins is a variable resistance, minimum 15kΩ, to an approximately 1V source. Figure 3b — Termination Current Tolerance vs. Programming Resistance, High Resistance Range The input will float to mid range whenever the external driver sinks or sources less than 5μA, a common worstcase characteristic of a high impedance GPIO, or a weak pull-up or pull-down GPIO, configured as an input. The driving GPIO must be able to sink or source at least 75μA to ensure a low or high state, respectively, although the drive current is typically far less. (See the Electrical Characteristics table.) Mode Input The MODE pin is a tri-level logical input. When driven high (VMODE > Min VIH), the SC811/3 will operate in USB High Power mode. If the MODE input voltage is within its specified mid range (Min VIM < VENB < Max VIM), either by floating (by reconfiguring its GPIO as an input) or by being externally forced, the SC811/3 will operate in USB Low Power mode. When driven low (VMODE < Max VIL), the SC811/3 will operate in adapter mode. When there is no charging source present, when the charger is disabled, or when operating in the monitor state (described in a later section), the MODE pin enters a high impedance state, suspending the tri-level functionality. Upon re-charge or re-enabling the charger, the MODE pin tri-level interface is reactivated. Typically a processor GPIO port direction defaults to input upon processor reset, or is high impedance when unpowered. This is the ideal initial condition for driving the MODE pin, since this will select USB Low Power mode, © 2008 Semtech Corporation 15 SC811 / SC813 Applications Information (continued) which is the safest default mode with the lowest fastcharge current. Enable Input The ENB pin is a tri-level logical input that allows selection of the following behaviors: • • • charging enabled with float-charging after termination (ENB = low range) charging enabled with float-charging disabled and battery monitoring at termination (ENB = mid range) charging disabled (ENB = high range). If the ENB input voltage is permitted to float to mid-range, the charger is enabled but it will turn off its output following charge termination and will enter the monitor state. This state is explained in the next section. Mid-range can be selected either by floating the input (sourcing or sinking less than 5μA) or by being externally forced such that VENB falls within the midrange limits specified in the Electrical Characteristics table. When driven low (VENB < Max VIL), the charger is enabled and will continue to float-charge the battery following termination. If the charger is already in monitor state following a previous termination, it will exit the monitor state and begin float-charging. When ENB is driven high (VENB > Min VIH), the charger is disabled and the ENB input pin enters a high impedance state, suspending tri-level functionality. The specified high level input current IIH is required only until a high level is recognized by the SC811/3 internal logic. The trilevel float circuitry is then disabled and the ENB input becomes high impedance. Once forced high, the ENB pin will not float to mid range. To restore tri-level operation, the ENB pin must first be pulled down to mid or low range (at least to VENB < Max VIM), then, if desired, released (by reconfiguring the GPIO as an input) to select mid-range. If the ENB GPIO has a weak pull-down when configured as an input, then it is unnecessary to drive ENB low to restore tri-level operation; simply configure the GPIO as an input. When the ENB selection changes from high-range to midor low-range, a new charge cycle begins and STATB goes low. Note that if a GPIO with a weak pull-up input configuration is used, its pull-up current will flow from the GPIO into the ENB pin while it is floating to mid-range. Since the GPIO is driving a 1V equivalent voltage source through a resistance (looking into ENB), this current is small — possibly less than 1μA. 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 impedance (CMOS) configuration or a weak pulldown when configured as an input. When pulled below the float voltage, the ENB pin output current is sourced from VIN, not from the battery. Monitor State If the ENB pin is floating, 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 (VCV - VReQ) while in the monitor state, the charger will automatically initiate a recharge cycle. The battery leakage current during monitor state is no more than 1μA over temperature and typically less than 0.1μA 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 SC811/3 can be forced from the monitor state (no float-charging) directly to floatcharging 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 float to midrange, the charger will remain on only until the output current becomes less than the termination current, and charging terminates. The SC811/3 turns off its charging output and returns to the monitor state within a millisecond. This forced re-charge behavior is useful for periodically testing the battery state-of-charge and topping-off the battery, without float-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 © 2008 Semtech Corporation 16 SC811 / SC813 Applications Information (continued) 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 input is applied and the VIN voltage is greater than the UVLO level and less than the OVP level of the selected mode. 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 (high voltage) range. STATB is subsequently released when the termination current is reached to indicate end-of-charge, when the ENB input is driven high to disable charging, or when the input voltage is removed. If the battery is already fully charged when a charge cycle is initiated, STATB is asserted, and will remain asserted for approximately 750μs 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 SC811/3 differs from monolithic linear single cell Liion chargers that implement a linear transition from CC to CV regulation. The linear transition method uses two simultaneous feedback signals — output voltage and output current — to the closed-loop controller. When the output voltage is sufficiently below the CV regulation voltage, the influence 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 influence 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 effectively reduces the charge current below that which is permitted for a portion of the charge cycle, which increases charge time. In the SC811/3, 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 difference between the transition voltage and the regulation 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 mode-dependent 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 specified 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 SC811/3. The thermal limiting controller reduces the output current by iT ≈ 50mA/ºC for any junction temperature TJ > T TL. When thermal limiting is inactive, TJ = TA + VΔ IFQ θJA, where VΔ is the voltage difference between the VIN pin and the BAT pin. However, if TJ computed this way exceeds T TL, then thermal limiting will become active and the thermal limiting regulation junction temperature will be TJTL = TA + VΔ I(TJTL) θJA, where I(TJTL) = IFQ − iT (TJTL − T TL). © 2008 Semtech Corporation 17 SC811 / SC813 Applications Information (continued) Combining these two equations and solving for TJTL, the steady state junction temperature during active thermal limiting is TJTL TA V IFQ _ x iT TTL 1 V iT JA JA 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(TJTL), reducing power dissipation such that die temperature equilibrium TJTL is reached. 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 dissipation can be greatly reduced by operating the charging adapter in current limit. The SC811/3 adapter mode supports adapter-current-limited charging with a low UVLO falling threshold and with internal circuitry designed for low input voltage operation. To operate an adapter in current limit, RIPRGM is chosen such that the adapter input programmed fast-charge current IFQ_AD exceeds the current limit of the charging adapter IAD-LIM. Note that if IAD-LIM is less than 20% of IFQ_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 IFQ_AD at least until the battery voltage exceeds the pre-charge threshold. 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 internal reference voltage to below the battery voltage. This will prematurely advance the charger logic from precharge current regulation to fast-charge regulation, and the charge current will exceed the safe level recommended for pre-charge conditioning. The low UVLO falling threshold (VTADUVLO-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 SC811/3 should be operated with adapter voltage below the rising selection threshold (VTADUVLO-R) only if the low input voltage is the result of adapter current limiting. This implies that the VIN voltage first exceeds VTADUVLO-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 mode fast-charge current be programmed greater than the maximum adapter current, (IAD-LIM). In this configuration, the CC regulator will operate with its pass device fully on (in saturation, also called “dropout”). The voltage drop from VIN to BAT is determined by the product of the minimum RDS-ON of the pass device multiplied by the adapter supply current. In dropout, the power dissipation in the SC811/3 is PILIM = (minimum RDS-ON) x (IAD-LIM)2. Since minimum RDS-ON does not vary with battery voltage, dropout power dissipation is constant throughout the CC portion of the charge cycle while the adapter remains in current limit. The SC811/3 junction temperature will rise above ambient by PILIM x θJA. If the device temperature rises to the temperature at which the thermal limiting control loop limits charging current (rather than the current being limited by the adapter), the input voltage will rise to the adapter regulation voltage. The power dissipation will increase so that the thermal limit regulation will further limit charge current. This will keep the adapter in voltage regulation for the remainder of the charge cycle. To ensure that the adapter remains in current limit, the internal device temperature must never rise to T TL. This implies that θJA must be kept small enough to ensure that TJ = TA + (PILIM × θJA) < T TL. Under-Voltage Load Regulation in USB Modes VIN pin UVLR in either USB mode prevents the battery charging current from overloading the USB Vbus network, regardless of the programmed fast-charge value. When USB High Power or USB Low Power mode is selected, the SC811/3 monitors the input voltage (VVIN) and reduces the charge current as necessary to keep VVIN at or above the UVLR limit (VUVLR). UVLR operates like a fourth output con- © 2008 Semtech Corporation 18 SC811 / SC813 Applications Information (continued) straint (along with CC, CV, and CT constraints), but it is active only when one of the USB modes is selected. In either of the USB modes, if the VIN voltage is externally pulled below VUVLR, the UVLR feature will reduce the charging current to zero. This condition will not be interpreted as termination and will not result in an end-of-charge indication. The STATB pin will remain asserted as if charging is continuing. This behavior prevents repetitive indications of end-of-charge alternating with start-of-charge in the case that the external VIN load is removed or is intermittent. The OVP threshold of the SC811 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 SC811. This behavior is illustrated in Figure 4, in which V BAT = 3.0V, I FQ = 700mA, and V VIN is stepped from 0V to 8.1V. Initially, power dissipation in the SC811 is 3.6W. VVIN=8.1V, VBAT=3.0V USB High Power and Low Power Support The USB specification 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 specification restricts the Vbus load to 500mA for high power devices after granting permission to operate as a high power device. A fixed 1:5 ratio of low power to high power charging current is desirable for charging batteries with maximum fast-charge current of at least 500mA. For this application, the SC811/3 provides fixed 1:5 current ratio low-to-high power mode support, via the tri-level MODE input pin. IBAT=700mA (Initially), PDISSIPATION=3.6W (Initially) IBAT (100mA/div) VVIN (2V/div) VBAT (2V/div) VVIN ,VBAT=0V— IBAT=0mA— 1s/div Figure 4 — SC811 Thermal Limiting Example For batteries with maximum fast-charge current less than 500mA, a fixed 1:5 low/high power charge current ratio will result in suboptimal charging in USB low power mode. For example, a 250mAh battery will typically require a fast-charge current of 250mA or less. A fixed 1:5 ratio for USB low-to-high power charging current will unnecessarily reduce charging current to 50mA, well below the 100mA permitted. In this case, it may be preferable to program USB low-power fast-charge current by switching an external programming resistor. See the section Design Considerations — Small Battery. 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 conduction of heat from the die to the ambient environment. The fast thermal limiting feature ensures compliance with CCSA YD/T 1591-2006, Telecommunication Industrial Standard of the People’s Republic of China — Technical Requirements and Test Method of Charger and Interface for Mobile Telecommunication Terminal, Section 4.2.3.1. Input Over-Voltage Protection Alternatively, the SC813 is offered for users who want to limit OVP to a guaranteed maximum of 6V. The SC811 and SC813 are alike except for OVP threshold. The VIN pin is protected from over-voltage to at least 30V above GND. When the input voltage exceeds the OverVoltage Protection (OVP) rising threshold ( VTOVP-R ), charging is halted. When the input voltage falls below the OVP falling threshold (VTOVP-F), charging restarts. An OVP fault turns off the STATB output. STATB is turned on again when charging restarts. Short Circuit Protection The SC811/3 can tolerate a BAT pin short circuit to ground indefinitely. The current into a ground short is approximately 10mA. © 2008 Semtech Corporation 19 SC811 / SC813 Applications Information (continued) During charging, a short to ground applied to the active current programming pin (IPRGM or IPUSB) is detected, while a short to ground on the inactive programming pin is ignored. Pin-short detection on an active current programming pin forces the SC811/3 into reset, turning off the output. A pin-short on either programming pin will prevent startup regardless of the mode selected. When the IPRGM or IPUSB pin-short condition is removed, the charger begins normal operation automatically without input power cycling. Over-Current Protection Over-current protection is provided in all modes of operation, including CV regulation. The output current is limited to either the programmed pre-charge current limit value or the fast-charge current limit value, depending on the voltage at the output. • 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. Design Considerations — Large Battery A battery with a desired fast-charge current exceeding 500mA is most consistent with the USB fixed 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 configured for 800mA max (RIPRGM = 2.80kΩ). Select R IPUSB = 4.53kΩ to set USB high power fast-charge to 450mA, and the USB low power fast-charge set to 450/5 = 90mA. The MODE pin tri-level logical input can be used to select between USB high power and USB low power modes whenever a fixed 5:1 current ratio is desired. Operation Without a Battery The SC811/3 can be operated as a 4.2V LDO regulator without the battery present, for example, factory testing. If this use is anticipated, the output capacitance C BAT should be at least 2.2μF to ensure stability. To operate the charger without a battery, the ENB pin must be driven low or grounded. Capacitor Selection Low cost, low ESR ceramic capacitors such as the X5R and X7R dielectric material types are recommended. The BAT pin capacitor range is 1μF to 22μF. The VIN pin capacitor is typically between 0.1μF and 2.2μF, although larger values will not degrade performance. Capacitance must be evaluated at the expected bias voltage, 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. • • Design Considerations — Small Battery A battery with a desired fast-charge current less than 500mA will not be charged in minimum charge time when in USB low power mode of operation with a 1:5 low-tohigh power mode current ratio. A 300mAh battery can be used as an example with maximum fast-charge current of 300mA. In this example, the adapter input and USB input high power fast-charge currents should both be set to 300mA. The USB low power fast-charge current of, for example, 90mA, for a low-to-high power current ratio of 1:3.3, would provide a shorter charge time than the 60mA obtained with the fixed USB low-to-high power charging current ratio of 1:5. An arbitrary ratio of USB low-to-high power charging currents can be obtained using an external n-channel FET operated with a processor GPIO signal to engage a second parallel IPUSB resistor, while selecting high power mode (MODE pin driven high) for both low or high power charging. The external circuit is illustrated in Figure 5. IPUSB 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. 5 RIPUSB_HI USB Hi/Lo Power Select RIPUSB Figure 5. External programming of arbitrary USB high power and low power charge currents. © 2008 Semtech Corporation 20 SC811 / SC813 Applications Information (continued) For USB low power mode charging, the external transistor is turned off. The transistor is turned on when high power mode is desired. The effect of the switched parallel IPUSB resistor is to reduce the effective programming resistance and thus raise the fast-charge current. An open-drain GPIO can be used directly to engage the parallel resistor RIPUSB_HI. Care must be taken to ensure that the RDS-ON of the GPIO is considered in the selection of RIPUSB_HI. Also important is the part-to-part and temperature variation of the GPIO RDS-ON, and their contribution to the USB High Power charge current tolerance. Note also that IPUSB will be pulled up briefly 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 RIPUSB_HI during this event. While unlikely to do any harm, this effect must also be considered. Independent Programming of Termination Current The USB high power mode fast-charge current is limited to 1000mA, twice the USB high power load limit, and so this mode may also be used for general purpose adapter charging. The IPRGM pin resistance to ground determines the USB high power mode pre-charge current, and the termination threshold current for all modes. If adapter mode will not be used in the application, RIPRGM can be selected to program only the termination threshold current independently of the fast-charge current, which is programmed with RIPUSB. Note that USB high power mode invokes Under-Voltage Load Regulation, so if charging with an adapter in current limit, the input voltage can be pulled down no lower than VUVLR. USB-only Charging of Very Large Batteries The 300mAh battery example can be used to illustrate how this system works. The adapter mode and USB high power mode fast-charge currents should both be set to 300mA max. The USB input low power fast-charge current is 100mA max. Refer to the circuit in Figure 5 and the data of Figures 1a and 1b. For IFQ_AD = 300mA max, use RIPRGM = 7.50kΩ. A fixed IPUSB resistor of RIPUSB = 23.2kΩ programs IFQ_USB = 100mA max for USB low power charging. When a parallel resistor RIPUSB_HI = 11.0kΩ resistor is switched in, the equivalent IPUSB resistor is 7.50kΩ, for IFQ_USB = 300mA max. USB Low Power Mode Alternative Where a USB mode selection signal is not available, or for a low capacity battery 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. Then, with the MODE pin always configured for USB high power mode, the UVLR feature will ensure that the charging load on the VIN pin will never pull the USB Vbus supply voltage below VUVLR regardless of the host or hub supply limit. The UVLR limit voltage guarantees that the voltage of the USB Vbus supply will not be loaded below the low power voltage specification limit, as seen by any other low power devices connected to the same USB host or hub. The SC811/3 can support the charging of very large capacity batteries as high as 2Ah using a USB-only charging source. The IPRGM resistance lower limit of 2.05kΩ is intended to limit the fast-charge current while charging in adapter mode to less than 1A. If only USB charging modes will be used, then the IPRGM resistor can be chosen as low as 1kΩ. This extended programming range allows setting the USB high power mode pre-charge current as high as 400mA (still below the USB specification limit), and the charge termination current as high as 200mA. (Both of these currents are determined by RIPRGM.) Note that with RIPRGM < 2.05kΩ, adapter mode should not be used, as this can result in potentially destructive fast-charge current. The USB high power and USB low power fast-charge currents and the USB low power pre-charge current are determined by the resistance between IPUSB and GND to comply with USB specified current limits, and so are unaffected by the IPRGM resistor. Termination detection requires that the charger be in CV regulation. If the IPRGM-determined termination threshold current is set higher than the USB low power mode fast-charge current, for example, then charge termination will occur the instant that the battery voltage rises to VCV. Thus USB low power charging will behave as if trickle-charging until fully charged, a perfectly safe and acceptable, although slow, charging scenario. © 2008 Semtech Corporation 21 SC811 / SC813 Outline Drawing — MLPD-UT8 2x2 B D A DIM E PIN 1 INDICATOR (LASER MARK) A SEATING PLANE aaa C A2 A1 C A A1 A2 b D D1 E E1 e L N aaa bbb DIMENSIONS MILLIMETERS INCHES MIN NOM MAX MIN NOM MAX .020 0.60 .024 0.50 .000 .002 0.00 0.05 (.006) (0.1524) .007 .010 .012 0.18 0.25 0.30 .075 .079 .083 1.90 2.00 2.10 .061 .067 .071 1.55 1.70 1.80 .075 .079 .083 1.90 2.00 2.10 .026 .031 .035 0.65 0.80 0.90 .020 BSC 0.50 BSC .012 .014 .016 0.30 0.35 0.40 8 8 .003 0.08 .004 0.10 D1 1 2 LxN E/2 E1 N bxN bbb e C A B e/2 D/2 NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS THE TERMINALS. © 2008 Semtech Corporation 22 SC811 / SC813 Land Pattern — MLPD-UT8 2x2 H DIMENSIONS R (C) K G Z Y P DIM INCHES C (.077) (1.95) G .047 1.20 H .067 1.70 K .031 0.80 0.50 MILLIMETERS P .020 R .006 0.15 X .012 0.30 Y .030 0.75 Z .106 2.70 X NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. 3. THERMAL VIAS IN THE LAND PATTERN OF THE EXPOSED PAD SHALL BE CONNECTED TO A SYSTEM GROUND PLANE. FAILURE TO DO SO MAY COMPROMISE THE THERMAL AND/OR FUNCTIONAL PERFORMANCE OF THE DEVICE. Contact Information Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 Phone: (805) 498-2111 Fax: (805) 498-3804 www.semtech.com © 2008 Semtech Corporation 23