INTEGRATED CIRCUITS NE57607 Two-cell Lithium-ion battery protection with overcurrent, over- and under-voltage protection Product data 2001 Oct 03 Philips Semiconductors Product data Two-cell Lithium-ion battery protection with overcurrent, over- and under-voltage protection NE57607 GENERAL DESCRIPTION The NE57607 is a family of 2-cell Li-ion protection ICs. Its over- and under-voltage accuracy is trimmed to within ±25 mV (5%) and is available to match the requirements of all lithium-ion cells manufactured in the market today. The NE57607 comes in the small VSOP-8A package. FEATURES • Trimmed overvoltage trip point to within ±25 mV • Programmable overvoltage trip time delay • Trimmed undervoltage trip point to within ±25 mV • Very low undervoltage sleep quiescent current 0.05 mA • Discharge overcurrent cutoff • Low operating current (10 mA) • Very small package VSOP-8A APPLICATIONS • Cellular phones • Palmtop computers SIMPLIFIED DEVICE DIAGRAM + 8 7 5 CHARGER OR LOAD Li-ION CELL NE57607 6 Li-ION CELL 4 3 2 1 – SL01564 Figure 1. Simplified device diagram. 2001 Oct 03 2 853-2297 27198 Philips Semiconductors Product data Two-cell Lithium-ion battery protection with overcurrent, over- and under-voltage protection NE57607 ORDERING INFORMATION PACKAGE TYPE NUMBER NE57607XDH NAME DESCRIPTION TEMPERATURE RANGE VSOP-8A 8-pin surface mount small outline package –20 to +70 °C NOTE: The device has six protection parameter options, indicated by the X on the order code, and defined in the following table. TYPICAL PROTECTION PARAMETERS IN THE NE57600 FAMILY Tamb = 0 °C to 50 °C Part Number Overcharge detection voltage (V) Overcharge detection hysteresis voltage (mV) Over-discharge detection voltage (V) Over-discharge resumption voltage (V) Overcurrent detection voltage (mV) NE57607Y 4.350 220 ± 50 2.3 ± 0.1 3.5 ± 0.2 150 ± 15 NE57607C 4.295 TBD 2.3 ± 0.1 3.5 ± 0.2 150 ± 15 NE57607E 4.250 300 ± 50 2.3 ± 0.1 3.5 ± 0.2 150 ± 15 NE57607G 4.300 220 ± 50 2.0 ± 0.1 3.1 ± 0.2 140 ± 15 NE57607H 4.225 TBD 2.3 ± 0.1 3.5 ± 0.2 150 ± 15 NE57607K 4.350 220 ± 50 2.3 ± 0.1 3.5 ± 0.2 100 ± 15 Part number marking PIN DESCRIPTION Each device is marked with a four letter code. The first three letters in the top line of markings designate the product. The fourth letter, represented by “x”, is a date code. The remaining markings are manufacturing codes. Part Number Marking NE57607YDH AGDx NE57607CDH AGFx NE57607EDH AGHx NE57607GDH AGKx NE57607HDH AGLx NE57607KDH AGNx PIN PIN CONFIGURATION CF 1 8 VC2 DF 2 7 VCC CS 3 6 VC1 GND 4 5 CDLY TOP VIEW SL01565 Figure 2. Pin configuration. 2001 Oct 03 3 SYMBOL DESCRIPTION 1 CF Charge FET drive pin, must have common emitter NPN to drive FET gate. Overcharge detection output pin PNP open collector output 2 DF Discharge control FET (N-ch) control output pin. 3 CS Overcurrent detection input pin. Monitors discharge current equivalently by the voltage drop between discharge FET source and drain. Stops discharge when voltage between CS pin and GND pin goes above overcurrent detection threshold value, and holds until load is released. 4 GND Ground pin, or lower cell (C1) negative pin. 5 CDLY Overcharge detection dead time setting pin. Dead time can be set by adding a capacitor between TD and GND pins. 6 VC1 Voltage input for positive terminal of bottom cell (C10). Connection pin for lower cell (C1) positive electrode side and upper cell (C2) negative electrode side. 7 VCC Power supply input pin. 8 VC2 Voltage input for top terminal of upper cell (C2). Philips Semiconductors Product data Two-cell Lithium-ion battery protection with overcurrent, over- and under-voltage protection NE57607 MAXIMUM RATINGS SYMBOL PARAMETER Min. Max. UNIT –0.3 +18 V VIN(max) Input voltage VCF(max) Maximum CF pin voltage – VIN–0.6 V VCS(max) Maximum CS pin voltage – VIN–0.6 V Topr Operating ambient temperature range –20 +70 °C Tstg Storage temperature –40 +125 °C PD Power dissipation – 300 mW ELECTRICAL CHARACTERISTICS Tamb = 25 °C; VCEL = V4–V3 = V3–V2 = V2–V1 = V1–GND; VCC = 4VCEL, except where noted otherwise. SYMBOL PARAMETER CONDITIONS Tamb = 0 °C ∼ 50 °C Min. Typ. Max. UNIT 4.325 4.350 4.375 V 170 220 270 mV VOC Overcharge detection voltage VOC Overcharge detection hysteresis voltage VOD Overdischarge detection voltage 2.20 2.30 2.40 V IVC2(1) Consumption current 1 VC2 = VC1 = 1.0 V; VCS = 1.4 V – – 0.1 µA IVC2(2) Consumption current 2 VC2 = VC1 = 1.9 V; VCS = 3.2 V – 0.5 0.8 µA IVC23 Consumption current 3 VC2 = VC1 = 3.5 V – 15.0 20.0 µA IVC24 Consumption current 4 VC2 = VC1 = 4.5 V; ROC = 270 kΩ – – 150 µA IVC1 VC1 pin input current VC2 = VC1 = 3.5 V –0.3 0 0.3 µA VDF Overdischarge release voltage Discharge resume by voltage rise 3.30 3.50 3.70 V VGDH GD pin HIGH output voltage VC2 = VC1 = 3.5 V; IL = –10 µA VC2–0.3 VC2–0.2 – V VGDL GD pin LOW output voltage VC2 = VC1 = 3.5 V; IL = 10 µA – 0.2 0.3 V ICFH CF pin output current VC2 = VC1 = 4.5 V – 30 150 µA VCS1 Overcurrent detection threshold value VCS2 Short circuit threshold value When both battery pack pins are shorted Overcurrent release Load release: Load of 5MEG& or more between both battery pack pins tOC1 Overcurrent detection delay time 1 tOC2 Overcurrent detection delay time 2 tOD Overdischarge detection delay time tOCH Overcharge detection dead time CDLY = 0.18 µF; Note 2 VST Start-up voltage VC2 = VC1 = 2.5 V Note 1 135 150 165 mV 0.35 0.45 0.55 V 7 12 18 ms – 30 100 µs ms 8 13 20 0.5 1.0 1.5 s –0.24 –0.12 –0.04 V NOTES: 1. The short-circuit delay time is for the IC only. This time will increase with the discharge FET gate capacitance. The short-circuit condition may cause the cell voltage to collapse and lengthen the delay. 2. Calculate overcharge dead time according to the following formula: Talm – 5.55 × CTD (time expressed in seconds, capacitance in µF) 2001 Oct 03 4 Philips Semiconductors Product data Two-cell Lithium-ion battery protection with overcurrent, over- and under-voltage protection TECHNICAL DISCUSSION NE57607 Lithium cell operating characteristics The internal resistance of lithium cells is in the 100 mΩ range, compared to the 5–20 mΩ of the nickel-based batteries. This makes the Lithium-ion and polymer cells better for lower battery current applications (less than 1 ampere) as found in cellular and wireless telephones, palmtop and laptop computers, etc. Lithium cell safety Lithium-ion and lithium-polymer cells have a higher energy density than that of nickel-cadmium or nickel metal hydride cells and have a much lighter weight. This makes the lithium cells attractive for use in portable products. However, lithium cells require a protection circuit within the battery pack because certain operating conditions can be hazardous to the battery or the operator, if allowed to continue. The average operating voltage of a lithium-ion or polymer cell is 3.6 V as compared to the 1.2 V of NiCd and NiMH cells. The typical discharge curve for Lithium cell is shown in Figure 3. Lithium cells have a porous carbon or graphite anode where lithium ions can lodge themselves in the pores. The lithium ions are separated, which avoids the hazards of metallic lithium. OPEN-CIRCUIT CELL VOLTAGE (V) If the lithium cell is allowed to become overcharged, metallic lithium plates out onto the surface of the anode and volatile gas is generated within the cell. This creates a rapid-disassembly hazard (the battery ruptures). If the cell is allowed to over-discharge (Vcell less than approximately 2.3 V), then the copper metal from the cathode goes into the electrolyte solution. This shortens the cycle life of the cell, but presents no safety hazard. If the cell experiences excessive charge or discharge currents, as happens if the wrong charger is used, or if the terminals short circuit, the internal series resistance of the cell creates heating and generates the volatile gas which could rupture the battery. The protection circuit continuously monitors the cell voltage for an overcharged condition or an overdischarged condition. It also continuously monitors the output for an overcurrent condition. If any of these conditions are encountered, the protection circuit opens a series MOSFET switch to terminate the abnormal condition. The lithium cell protection circuit is placed within the battery pack very close to the cell. VOV 3.0 VUV 2.0 50 100 NORMALIZED CELL CAPACITY (%) SL01553 Figure 3. Lithium discharge curve. Charging control versus battery protection The battery pack industry does not recommend using the pack’s internal protection circuit to end the charging process. The external battery charger should have a charge termination circuit in it, such as that provided by the SA57611. This provides two levels of overcharge protection, with the primary protection of the external charge control circuit and the backup protection from the battery pack’s protection circuit. The charge termination circuit will be set to stop charging at a level around 50 mV less than the overvoltage threshold voltage of the battery pack’s own protection circuit. 2001 Oct 03 4.0 5 Philips Semiconductors Product data Two-cell Lithium-ion battery protection with overcurrent, over- and under-voltage protection NE57607 Charging Lithium cells The lithium cells must be charged with a dedicated charging IC such as the NE57600. These dedicated charging ICs perform a current-limited, constant-voltage charge, as shown in Figure 4. CHARGE CURRENT (%C) 1.0 The charger IC begins charging with a current that is typically the rating of the cell (1C) or the milliampere rating of the cell. As the cell approaches its full-charge voltage rating (VOV), the current entering the cell decreases, and the charger IC provides a constant voltage. When the charge current falls below a preset amount, 50 mA for example, the charge is discontinued. If charging is begun below the overdischarged voltage rating of the cell, it is important to slowly raise the cell voltage up to this overdischarged voltage level. This is done by a reconditioning charge. A small amount of current is provided to the cell (50 mA for example), and the cell voltage is allowed a period of time to rise to the overdischarged voltage. If the cell voltage recovers, then a normal charging sequence can begin. If the cell does not reach the overdischarged voltage level, then the cell is too damaged to charge and the charge is discontinued. 0.5 CONSTANT CURRENT CONSTANT VOLTAGE 1.0 2.0 TIME (HOURS) OPEN-CIRCUIT CELL VOLTAGE (V) Vov To take advantage of the larger energy density of lithium cells it is important to allow enough time to completely charge the cell. When the charger switches from constant current to constant voltage charge (Point B, Figure 4) the cell only contains about 80 percent of its full capacity. When the cell is 100 mV less than its full rated charge voltage the capacity contained within the cell is 95 percent. Hence, allowing the cell to slowly complete its charge takes advantage of the larger capacity of the lithium cells. 4.0 Point B 3.0 1.0 2.0 TIME (HOURS) SL01554 Figure 4. Lithium cell charging curves. FUNCTIONAL DIAGRAM 7 VC2 VCC 8 OV Ref UV Ref VC1 OV DEADTIME CONTROL 1 CF 5 CDLY 2 DF 6 OV Ref NE57607 UV Ref GND 4 CHARGER DETECTOR VCC UV DEADTIME CONTROL CS 3 OC Ref SL01566 Figure 5. Functional diagram. 2001 Oct 03 6 Philips Semiconductors Product data Two-cell Lithium-ion battery protection with overcurrent, over- and under-voltage protection NE57607 APPLICATION INFORMATION + 330 Ω 330 Ω 1 MΩ 8 7 5 CHARGER OR LOAD Li-ION CELL 1 kΩ NE57607 6 Li-ION CELL 4 3 2 1 10 kΩ 47 kΩ 0.1 µF 0.1 µF 0.1 µF 10 kΩ – SL01567 Figure 6. Typical application circuit The NE57607 drives the series N-Channel MOSFETs to states determined by each of the cell’s voltage and the battery pack load current. During normal periods of operation, both the discharge and charge MOSFETs are in the ON state, thus allowing bidirectional current flow. FET STATUS FOR NORMAL AND ABNORMAL CONDITIONS Operating Mode and Charging Condition If the battery pack is being charged, and either of the cell’s voltage exceeds the overvoltage threshold, then the charge MOSFET is turned OFF (FET towards the pack’s external terminal). The cell’s voltage must fall lower than the overvoltage hysteresis voltage (VOV(Hyst)) before the charge MOSFET is again turned ON. If the battery pack is being discharged and the undervoltage threshold (VUV(Th)) is exceeded, then the discharge MOSFET is turned OFF. It will not run back ON until a charger is applied to the pack’s external terminals AND the cell’s voltage rises above the undervoltage hysteresis voltage (VUV(Hyst)). Charge FET (CF) Discharge FET (DF) Normal (charging or discharging) ON ON Overcharge (charging) OFF ON Overcharge (discharging) ON ON Overdischarge (discharging) OFF OFF Overdischarge (charging) ON ON Overcurrent (charging or discharging) OFF OFF Normal mode: Overdischarge detection voltage < battery voltage <overcharge detection voltage When the battery pack is being discharged, the load current causes the voltage across the discharge MOSFET to increase past the overcurrent threshold voltage (VOC(Th)), then the discharge MOSFET is turned OFF after a fixed 7–18 ms delay. If short-circuit is placed across the pack’s terminals, then the discharge MOSFET is turned OFF after a 100–300 µs time delay to avoid damaging the MOSFETs. Discharge current < overcurrent detection level Overcharge mode: Battery voltage > overcharge detection voltage Overdischarge mode: Overdischarge detection voltage > battery voltage Overcurrent mode: Discharge current > overcurrent detection level voltage between VM and GND = discharge current × FET ON resistance (discharge or charge FET) 2001 Oct 03 7 Philips Semiconductors Product data Two-cell Lithium-ion battery protection with overcurrent, over- and under-voltage protection NE57607 though, is more defined by the total series resistance of the battery pack. The total resistance of the battery pack is given by Equation 1. The R-C filters around the NE57607 One needs to place R-C filters on the positive input pins of the NE57607. These are primarily to shield the IC from electrostatic occurrences and spikes on the terminals of the battery pack. A secondary need is during the occurrence of a short-circuit across the battery pack terminals. Here, the Li-ion cell voltage could collapse and cause the IC to enter an unpowered state. The R-Cs then provide power during the first instance of the short circuit and allow the IC to turn OFF the discharge MOSFET. The IC can then enter an unpowered state. Lastly, the R-C filter on the node between the two cells filters any noise voltage caused by noisy load current. Rbat(tot) = 2(RDS(ON)) + 2Rcell (Equation 1) The total pack resistance is typically determined by the system requirements. The total pack resistance directly determines how much voltage droop will occur during pulses in load current. Another consideration is the forward-biased safe operating area of the MOSFET. During a short-circuit, the discharge current can easily reach 10–15 times the “C-rating” of the cells. The MOSFET must survive this current prior to the discharge MOSFET can be turned OFF. So having an FBSOA envelope that exceeds 20 amperes for 5 ms would be safe. The values shown in Figure 6 are good for these purposes. Selecting the Optimum MOSFETs: The Charge MOSFET Circuit. For a 2-cell battery pack, a logic-level MOSFET should be used. These MOSFETs have turn-on thresholds of 0.9 V and are considered full-on at 4.5 V VGS. The total pack voltage will be a maximum of 8.6 V which is within safe operating range of the gate voltage which is typically more than two times the full-on voltage. The NE57607 uses an isolated charge MOSFET drive arrangement. This is to help keep ESD charges from entering the IC. The charge MOSFET is normally ON until turned off by the IC. The CF pin uses a current source to drive an external NPN transistor to turn OFF the charge FET. If a charge has poor “compliance” or the no load voltage of the charge can rise significantly above the rating of the battery pack. This condition causes the source of the charge FET to go very negative compared to the cell GND voltage after the charge FET opens. This design allows the charge FET gate drive to “float” down to this very negative voltage without upsetting the operation of the IC. The MOSFETs should have a voltage rating greater than 20 V and should have a high avalanche rating to survive any spikes generated across the battery pack terminals. The current rating of the MOSFETs should be greater than four times the maximum “C-rating” of the cells. The current rating, PACKING METHOD GUARD BAND TAPE REEL ASSEMBLY TAPE DETAIL COVER TAPE CARRIER TAPE BARCODE LABEL BOX SL01305 Figure 7. Tape and reel packing method. 2001 Oct 03 8 Philips Semiconductors Product data Two-cell Lithium-ion battery protection with overcurrent, over- and under-voltage protection NE57607 VSOP-8A: plastic small outline package; 8 leads; body width 4.4 mm A 1.35 1.15 1.15 0.23 0.21 0.16 0.10 3.4 2.8 4.6 4.2 6.7 6.1 VSOP-8A 2001 Oct 03 9 0.7 0.3 0.12 0.875 max. 10° 0° Philips Semiconductors Product data Two-cell Lithium-ion battery protection with overcurrent, over- and under-voltage protection NE57607 Data sheet status Data sheet status [1] Product status [2] Definitions Objective data Development This data sheet contains data from the objective specification for product development. Philips Semiconductors reserves the right to change the specification in any manner without notice. Preliminary data Qualification This data sheet contains data from the preliminary specification. Supplementary data will be published at a later date. Philips Semiconductors reserves the right to change the specification without notice, in order to improve the design and supply the best possible product. Product data Production This data sheet contains data from the product specification. Philips Semiconductors reserves the right to make changes at any time in order to improve the design, manufacturing and supply. Changes will be communicated according to the Customer Product/Process Change Notification (CPCN) procedure SNW-SQ-650A. [1] Please consult the most recently issued data sheet before initiating or completing a design. [2] The product status of the device(s) described in this data sheet may have changed since this data sheet was published. The latest information is available on the Internet at URL http://www.semiconductors.philips.com. Definitions Short-form specification — The data in a short-form specification is extracted from a full data sheet with the same type number and title. For detailed information see the relevant data sheet or data handbook. Limiting values definition — Limiting values given are in accordance with the Absolute Maximum Rating System (IEC 60134). Stress above one or more of the limiting values may cause permanent damage to the device. These are stress ratings only and operation of the device at these or at any other conditions above those given in the Characteristics sections of the specification is not implied. Exposure to limiting values for extended periods may affect device reliability. Application information — Applications that are described herein for any of these products are for illustrative purposes only. Philips Semiconductors make no representation or warranty that such applications will be suitable for the specified use without further testing or modification. Disclaimers Life support — These products are not designed for use in life support appliances, devices or systems where malfunction of these products can reasonably be expected to result in personal injury. Philips Semiconductors customers using or selling these products for use in such applications do so at their own risk and agree to fully indemnify Philips Semiconductors for any damages resulting from such application. Right to make changes — Philips Semiconductors reserves the right to make changes, without notice, in the products, including circuits, standard cells, and/or software, described or contained herein in order to improve design and/or performance. Philips Semiconductors assumes no responsibility or liability for the use of any of these products, conveys no license or title under any patent, copyright, or mask work right to these products, and makes no representations or warranties that these products are free from patent, copyright, or mask work right infringement, unless otherwise specified. Koninklijke Philips Electronics N.V. 2001 All rights reserved. Printed in U.S.A. Contact information For additional information please visit http://www.semiconductors.philips.com. Fax: +31 40 27 24825 Date of release: 10-01 For sales offices addresses send e-mail to: [email protected]. 2001 Oct 03 Document order number: 10 9397 750 08993