ACE4717 5A Lead-Acid Battery Charger IC Description The ACE4717 is a PWM switch-mode battery charger controller for lead-acid battery in a small package using few external components. The ACE4717 is specially designed for charging lead-acid battery with trickle charge, constant current charge, over-charge and float charge mode. In over-charge and float charge mode, the regulation voltage is set by the external resistor divider. The constant charging current is programmable with a single sense resistor. Deeply discharged batteries are automatically trickle charged at 19% of the programmed constant charging current until the cell voltage exceeds 75.6% of the regulation voltage in over-charge mode. The over-charge is terminated once the charging current drops to a level set by an on-chip resistor and an external resistor, then ACE4717 will enter into float charge mode. A new charge cycle automatically restarts if the battery voltage falls below 82.2% of the over-charge voltage in float-charge mode. ACE4717 will automatically enter sleep mode when input voltage is lower than battery voltage. Other features include undervoltage lockout, battery temperature monitoring and status indication, etc. Features Wide Input Voltage: 7.5V to 28V Complete Charger Controller for Lead-Acid Battery Charge Current Up to 5A High PWM Switching Frequency: 300KHz Over-Charge Voltage Set By the External Resistor Divider Charging Current is programmed with a sense resistor Automatic Conditioning of Deeply Discharged Batteries Over-charge Termination Current can be set by an external resistor Battery Temperature Monitoring Automatic Recharge Charger Status Indication Soft Start Battery Overvoltage Protection Operating Ambient Temperature -40℃ to ＋85℃ Application Lead-Acid Battery Charger UPS Portable Industrial and Medical Equipment Standalone Battery Chargers VER 1.2 1 ACE4717 5A Lead-Acid Battery Charger IC Absolute Maximum Ratings Parameter Max Unit Voltage from VCC, VG, DRV, CHRG, DONE to GND -0.3 ~ 30 V Voltage from CSP, BAT to GND -0.3 ~ 28 V Voltage from COM3 to GND 6.5 V Voltage from Other Pins to GND -0.3 ~ VCOM3+0.3 μA Storage Temperature -65 ~ 150 ℃ Operating Ambient Temperature -40 ~ 85 ℃ Lead Temperature (Soldering, 10 seconds) 300 ℃ Stresses beyond those listed under ‘Absolute Maximum Ratings’ may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these or any other conditions above those indicated in the operational sections of the specifications is not implied. Exposure to Absolute Maximum Rating Conditions for extended periods may affect device reliability. Packaging Type TSSOP-16 TSSOP-16 Description Function 1 VG 2 PGND Internal Voltage Regulator. VG internally supplies power to gate driver, connect a 100nF capacitor between VG pin and VCC pin. Power Ground. 3 GND Analog Ground. 4 CHRG 5 DONE Open-Drain Output. When the battery is being charged, this pin is pulled low by an internal switch. Otherwise this pin is in high impedance state. Open-Drain Output. When the charging is terminated, this pin is pulled low by an internal switch. Otherwise this pin is in high impedance state. Battery Temperature Monitoring Input. Connect an NTC resistor from this pin 6 TEMP to GND. Temperature anomalies only in trickle, constant current, overcharge stage. VER 1.2 2 ACE4717 5A Lead-Acid Battery Charger IC 7 EOC 8 COM 1 9 COM 2 10 FB 11 COM 3 12 NC 13 CSP 14 BAT End-of-Over Charge Current Setting Pin. Connect this pin to GND directly or via a resistor to set the over charge current . Loop Compensation Input 1. Connect a 470pF capacitor from this pin to GND. Loop Compensation Input 2. Connect a 220nF capacitor in series with an 120Ω resistor from this pin to GND. Battery Voltage Feedback Input. Need to connect to the external resistor divider in order to set the over-charge and float-charge voltage. Loop Compensation Input 3. Connect an 100nF capacitor from this pin to GND. No Connection Positive Input for Charging Current Sensing. This pin and the BAT pin measure the voltage drop across the sense resistor RCS to provide the current signals required. Negative Input for Charging Current Sensing. BAT and CSP pin measure the voltage drop across the sense resistor RCS to provide the current signals required. 15 VCC 16 DRV External DC Power Supply Input. VCC is also the power supply for internal circuit. Bypass this pin with a capacitor. Drive the gate of external P-channel MOSFET. VER 1.2 3 ACE4717 5A Lead-Acid Battery Charger IC Typical Application Circuit ACE4717 Figure 1 Typical Application Circuit Ordering information ACE4717 XX + H Halogen - free Pb - free LM : TSSOP-16 VER 1.2 4 ACE4717 5A Lead-Acid Battery Charger IC Electrical Characteristics VCC=15V,TA=-40~85℃, unless otherwise noted. Parameter Symbol Conditions Max Units Input Supply Voltage VCC 7.5 28 V Undervoltage lockout Threshold UVLO 4.2 6 7.3 V Operating Current IVCC VBAT > VOC (Note1) 1.2 1.7 2.2 mA FB Pin Bias Current IFB VFB＝4V 40 260 nA 113 120 127 VBAT<81.8V*VOC (Note1) 13 23 33 5 10 15 VBAT>81.8V*VOC Min (Note1) Typ Current Sense Voltage (VCSP－VBAT) VCS Current into BAT Pin IBAT VBAT＝12V Precharge Threshold VPRE VFB rising 75.6% Recharge Threshold VFloat Float charge mode 93.6% Recharge Threshold VRE VFB falling 82.2% Overvoltage Trip Level Vov VBAT rising 1.06 1.08 1.1 Overvoltage Clear Level Vclr VBAT falling 0.98 1 1.02 41 50 65 uA mV uA VOC (Note 1) Temp Pin Pull up Current Iup High Threshold Vthh TEMP Voltage Rising 1.57 1.61 1.65 V Low Threshold Vthl TEMP Voltage Falling 0.145 0.175 0.205 V 3.64 3.69 3.74 V Feedback Voltage FB Pin TC Over Charge Mode FB pin , Over Charge VFB mode FB pin , Over Charge TCFB mode Float Charge Mode Feedback Voltage VFB FB Pin TC TCFB CHRG Pin Sink Current CHRG Leakage Current DONE Sink Current DONE Leakage Current ICHRG ILK1 IDONE ILK2 FB pin , Float Charge mode FB pin , Float Charge mode CHRG Pin VCHRG=1V, charge mode VCHRG=25V, termination mode DONE Pin VDONE=1V, termination mode VDON=25V, charge mode 7 7 -5.56mV /℃ 3.46 V -5mV /℃ 12 12 18 mA 1 uA 18 mA 1 uA VER 1.2 5 ACE4717 5A Lead-Acid Battery Charger IC Oscillator Switching Frequency fosc Maximum Duty Cycle Dmax 240 300 360 94 kHZ % Sleep Mode Sleep Mode Threshold (measure VCC-VBAT) VSLP VCC falling Sleep mode Release Threshold (measure VCC-VBAT) VSLPR VCC rising VBAT=8V VBAT=12V VBAT=18V VBAT=8V VBAT=12V VBAT=18V 0.06 0.1 0.18 0.26 0.32 0.38 0.1 0.14 0.23 0.32 0.42 0.47 0.14 0.18 0.28 0.39 0.52 0.58 V V DRV Pin VDRV High (VCC－VDRV) VH IDRV＝-10mA VDRV Low (VCC－VDRV) VL Rise Time tr Fall Time tf IDRV＝0mA Cload＝2nF, 10% to 90% Cload＝2nF, 90% to 10% 60 mV 5 6.5 8 V 30 40 65 Ns 30 40 65 ns Note 1: VOC is the regulation voltage at BAT pin in constant voltage mode Detailed Description The ACE4717 is a trickle charge, constant current, over voltage, float voltage battery charger controller that adopts PWM step-down (buck) switching architecture, the device is specially designed for lead-acid battery. The charge current is set by an external sense resistor (RCS) across the CSP and BAT pins. The final battery regulation voltage VREG in constant voltage mode is set by the external resistor divider. A charge cycle begins when the voltage at the VCC pin rises above the UVLO level and is greater than the battery voltage. At the beginning of the charge cycle, if the battery voltage is less than 75.6%*Voc, the charger goes into trickle charge mode. The trickle charge current is about 19% of the full charge current. In constant current mode, the charge current is set by the internal 120mV reference voltage and a external resistor RCS, the constant current is 120mV/RCS. In constant current mode, ACE4717 will remain in constant current mode even though the battery drops below 75.6% of the over charge voltage. When the battery voltage approaches the over-charge voltage, the charger goes into the over charge mode. In over charge mode, the charge current start to decrease and when the charge current drops to a level that is set by the resistor at EOC pin, the charger goes into float-charge mode, the BAT pin voltage in float-charge mode is 93.6% of that in over-charge mode. In trickle charge, constant current and over-charge mode, CHRG pin is pulled low by an internal N-channel MOSFET to indicate that the charge cycle is ongoing, and CHRG pin is in high impedance state. During the float-charge mode, DONE s pulled low by an internal N-channel MOSFET to indicate the float-charge mode, CHRG in is in high impedance state. In float-charge mode to restart the charge cycle, just remove and reapply the input voltage. Also, a new charge cycle will begin if the battery voltage drops below the recharge threshold voltage of 82.2%*VOC. When the input voltage is not present, the charger goes into sleep mode. VER 1.2 6 ACE4717 5A Lead-Acid Battery Charger IC A 10kΩ NTC (negative temperature coefficient) thermistor can be connected from the TEMP pin to ground for battery temperature qualification. If the battery temperature is outside the normal range, trickle charge, constant current charging, overcharge stage charging process will be suspended. An over-voltage comparator guards against voltage transient overshoots (8% of over-charge voltage). In this case, P-channel MOSFET is turned off until the overvoltage condition is cleared. This feature is useful for battery load dump or sudden removal of battery. The charging profile is shown in Figure 2. Figure 2 The Charging Profile Application Information Undervoltage Lockout (UVLO) An undervoltage lockout circuit monitors the input voltage and keeps the charger off if VCC falls below 6V(Typical). Set the Over Voltage in Over Voltage Mode As shown in Figure 1, battery voltage is feedback to FB pin via the resistor divider composed of R6 and R7. ACE4717 decided the charging status based on FB’s voltage. When FB’s voltage approaches 3.69V, the charger goes into over-voltage mode. In over-voltage mode, the charge current decrease gradually, and the battery voltage remains unchanged. In light of FB pin’s bias current, the regulation voltage in over-voltage mode is determined by the following equation: VBAT＝3.69*(1＋R7/R6)＋IB*R7 Where, IB is FB pin’s bias current, which is 40nA typical. From the above equation, we can see that an error is introduced due to the existence of bias current IB, the error is IB*R7. If R7＝500KΩ, then the error is about 20mV. So the error should be taken into account while designing the resistor divider. The maximum over-charge voltage that can be set is 25V. VER 1.2 7 ACE4717 5A Lead-Acid Battery Charger IC Trickle Charge Mode At the beginning of a charge cycle, if the battery voltage is below 75.6%*VOC, the charger goes into trickle charge mode with the charge current set at 19% of the constant current. In constant current mode, ACE4717 will remain in constant current mode even though the battery drops below 75.6% of the over charge voltage. Charge Current Setting The constant charge current, namely the charge current in constant current mode, is decided by the following formula: Where: ICH is the constant charge current RCS is the resistor between the CSP pin and BAT pin End-of-Over Charge Current Setting End-of-over charge current can be set by connecting a resistor from EOC pin to GND, and is decided by the following equation: Where: IEOC is the end-of-over charge current in Ampere Rext is the external resistance from EOC pin to GND in Ω. Rext can not be great than 100KΩ, therwise the charging may not be terminated correctly. RCS is the current sense resistance between CSP pin and BAT pin in Ω It is our interest to calculate the ratio between IEOC and ICH: When Rext=0Ω, the minimum IEOC/ICH=10.5% When Rext=100KΩ, the maximum IEOC/ICH=83.5% Float Charge Voltage Mode After the over voltage charge is terminated, the charger goes into float charge mode. In float charge mode, the battery voltage drops to 93.6%*VOC. Float charge mode can compensate for the loss of battery power due to self-discharge or external loading. Automatic Battery Recharge In float voltage charge mode, if both the battery and the input power supply (wall adapter) are present, a new charge cycle will begin if the battery voltage drops below 82.2%*VOC due to self-discharge or external loading. VER 1.2 8 ACE4717 5A Lead-Acid Battery Charger IC Battery Temperature Monitoring A negative temperature coefficient (NTC) thermistor located close to the battery pack can be used to monitor battery temperature and will not allow charging unless the battery temperature is within an acceptable range. Connect a 10kΩ thermistor from the TEMP pin to ground. Internally, for hot temperature, the low voltage threshold is set at 175mV which is equal to 50℃(RNTC≈3.5kΩ). For cold temperature, the high voltage threshold is set at 1.61V which is equal to 0℃(RNTC≈32kΩ) with 50uA of pull-up current. Once the temperature is outside the window, the charge cycle will be suspended, and the charge cycle resumes if the temperature is back to the acceptable range. The TEMP pin’s pull up current is about 50uA, so the NTC thermistor’s resistance should be 10kΩ at 25℃, about 3.5kΩ at hot temperature threshold, and about 32kΩ at cold temperature threshold. The NTC thermistor such as TH11-3H103F, MF52(10 kΩ), QWX-103 and NCP18XH103F03RB can work well with ACE4717. The above mentioned part numbers are for reference only, the users can select the right NTC thermistor part number based on their requirements. If battery temperature monitoring function is not needed, just connect a 10KΩ resistor from TEMP pin to GND. Status Indication The ACE4717 has 2 open-drain status outputs: CHRG and DONE. CHRG is pulled low when the charger is in charging status, otherwise CHRG becomes high impedance. DONE is pulled low if the charger is in floatcharge mode, otherwise DONE becomes high impedance. When the battery is not present, the charger charges the output capacitor to the float-charge voltage. The open drain pin that is not used should be tied to ground. The table 1 lists the two indicator status and its corresponding charging status. It is supposed that red LED is connected to CHRG pin and green LED is connected to DONE pin. CHRG Pin Low (The red LED on) High Impedance (the red LED off) High Impedance (the red LED off) DONE pin High Impedance (the green LED off) Low (the green LED on) State Description Trickle ,constant current or over-charge Float Charging There are three possible state: * The voltage at the VCC pin below the High Impedance (the green UVLO level LED off) * The voltage at the VCC pin below VBAT * abnormal battery’s temp Table 1 Indication Status VER 1.2 9 ACE4717 5A Lead-Acid Battery Charger IC Gate Drive The ACE4717’s gate driver can provide high transient currents to drive the external pass transistor. The rise and fall times are typically 40ns when driving a 2000pF load, which is typical for a P-channel MOSFET with Rds(on) in the range of 50mΩ. A voltage clamp is added to limit the gate drive to 8V max. below VCC. For example, if VCC is 20V, then the DRV pin output will be pulled down to 12V min. This allows low voltage P-channel MOSFETs with superior Rds(on) to be used as the pass transistor thus increasing efficiency. Loop Compensation In order to make sure that the current loop and the voltage loop are stable, the following compensation components are necessary: (1) A 470pF capacitor from the COM1 pin to GND (2) A series 220nF ceramic capacitor and 120Ω resistor from the COM2 pin to GND (3) An 100nF ceramic capacitor from the COM3 pin to GND (4) The capacitance C7 in Figure 1 can be roughly calculated by：C7＝8*(R6/R7) (pF) Input and Output Capacitors Since the input capacitor is assumed to absorb all input switching ripple current in the converter, it must have an adequate ripple current rating. Worst-case RMS ripple current is approximately one-half of output charge current. The selection of output capacitor is primarily determined by the ESR required to minimize ripple voltage and load step transients. Generally speaking, a 10uF ceramic capacitor can be used. Inductor Selection During P-channel MOSFET’s on time, the inductor current increases, and decreases during P-channel MOSFET’s off time, the inductor’s ripple current increases with lower inductance and higher input voltage. Higher inductor ripple current results in higher charge current ripple and greater core losses. So the inductor’s ripple current should be limited within a reasonable range. The inductor’s ripple current is given by the following formula: Where, f is the switching frequency 300KHz L is the inductor value VBAT is the battery voltage VCC is the input voltage A reasonable starting point for setting inductor ripple current is △IL＝0.4*ICH, ICH is the charge current. Remember that the maximum △IL occurs at the maximum input voltage and the lowest inductor value. So lower charge current generally calls for larger inductor value. VER 1.2 10 ACE4717 5A Lead-Acid Battery Charger IC Use Table 2 as a guide for selecting the correct inductor value for your application. Charge Current Input Voltage Inductor Value 1A 2A 3A 4A 5A >20V 40uH <20V 30uH >20V 30uH <20V 20uH >20V 20uH <20V 15uH >20V 15uH <20V 10uH >20V 10uH <20V 8uH Table 2 Guide to Select Inductor Value MOSFET Selection The ACE4717 uses a P-channel power MOSFET switch. The MOSFET must be selected to meet the efficiency or power dissipation requirements of the charging circuit as well as the maximum temperature of the MOSFET. The peak-to-peak gate drive voltage is set internally, this voltage is typically 6V. Consequently, logic-level threshold MOSFETs must be used. Pay close attention to the BVDSS specification for the MOSFET as well; many of the logic level MOSFETs are limited to 30V or less. Selection criteria for the power MOSFET includes the “on” resistance Rds(on), total gate charge Qg, reverse transfer capacitance CRSS, input voltage and maximum charge current. The MOSFET power dissipation at maximum output current is approximated by the equation: Where: Pd is the power dissipation of the power MOSFET VBAT is the maximum battery voltage VCC is the minimum input voltage Rds(on) is the power MOSFET’s on resistance at room temperature ICH is the charge current dT is the temperature difference between actual ambient temperature and room temperature(25℃) In addition to the I2Rds(on) loss, the power MOSFET still has transition loss, which are highest at the highest input voltage. Generally speaking, for VIN＜20V, the I2Rds(on) loss may be dominant, so the MOSFET with lower Rds(on) should be selected for better efficiency; for VIN＞20V, the transition loss may be dominant, so the MOSFET with lower CRSS can provide better efficiency. CRSS is usually specified in the MOSFET characteristics; if not, then CRSS can be calculated using CRSS = QGD/ΔVDS. The MOSFETs such as AO4459, STM9435(or WT9435), AO3407A can be used. The part numbers listed above are for reference only, the users can select the right MOSFET based on their requirements. VER 1.2 11 ACE4717 5A Lead-Acid Battery Charger IC Diode Selection The diodes D1 and D2 in Figure 1 are schottky diode, the current rating of the diodes should be at least the charge current limit, the voltage rating of the diode should exceed the maximum expected input voltage. The diode that is much larger than that is sufficient can result in larger transition losses due to their larger junction capacitance. About Battery Current in Sleep Mode In the typical application circuit shown in Figure 1, when input voltage is powered off or lower than battery voltage, ACE4717 will enter sleep mode. In sleep mode, the battery current includes: (1) The current into BAT pin and CSP pin, which is about 10uA(VBAT＝12V). (2) The current from battery to VCC pin via diode D1, which is determined by D1’s leakage current. The current will charge capacitance C1 at VCC pin, which will make VCC voltage a bit higher. To avoid erratic operation, a resistor in parallel with capacitance C1 may be needed to discharge the capacitance, the resistor value is determined by diode D1’s leakage, generally speaking, a 20KΩ resistor can achieve the task. (3) The current from battery to GND via diode D2, which is also determined by D2’s leakage current. PCB Layout Considerations When laying out the printed circuit board, the following considerations should be taken to ensure proper operation of the IC. (1) To minimize radiation, the 2 diodes, pass transistor, inductor and the input bypass capacitor traces should be kept as short as possible. The positive side of the input capacitor should be close to the source of the P-channel MOSFET; it provides the AC current to the pass transistor. The connection between the catch diode and the pass transistor should also be kept as short as possible. (2) The compensation capacitor connected at the COM1, COM2 and COM3 pins should return to the analog ground pin of the IC. This will prevent ground noise from disrupting the loop stability. (3) Output capacitor ground connections need to feed into same copper that connects to the input capacitor ground before tying back into system ground. (4) Analog ground and power ground(or switching ground) should return to system ground separately. (5) The ground pins also works as a heat sink, therefore use a generous amount of copper around the ground pins. This is especially important for high VCC and/or high gate capacitance applications. (6) Place the charge current sense resistor RCS right next to the inductor output but oriented such that the IC’s CSP and BAT traces going to RCS are not long. The 2 traces need to be routed together as a single pair on the same layer at any given time with smallest trace spacing possible. (7) The CSP and BAT pins should be connected directly to the current sense resistor (Kelvin sensing) for best charge current accuracy. See Figure 3 as an example. Figure 3 Kelvin Sensing of Charge Current VER 1.2 12 ACE4717 5A Lead-Acid Battery Charger IC Packing Information TSSOP-16 Symbol Dimensions n Millimeters Dimensions In Inches Min Max Min Max D 4.900 5.100 0.193 0.201 E 4.300 4.500 0.169 0.177 b 0.190 0.300 0.007 0.012 c 0.090 0.200 0.004 0.008 E1 6.250 6.550 0.246 0.258 A 1.100 0.043 A2 0.800 1.000 0.031 0.039 A1 0.020 0.50 0.001 0.006 e L 0.65 (BSC) 0.500 H Θ 0.026 (BSC) 0.700 0.020 0.25 (TYP) 。 1 0.028 0.01 (TYP) 。 7 。 1 。 7 VER 1.2 13 ACE4717 5A Lead-Acid Battery Charger IC Notes ACE does not assume any responsibility for use as critical components in life support devices or systems without the express written approval of the president and general counsel of ACE Electronics Co., LTD. As sued herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and shoes failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. ACE Technology Co., LTD. http://www.ace-ele.com/ VER 1.2 14