MAX38886ATD+

Click here for production status of specific part numbers. MAX38886 2.5V to 5.0V, 0.5A/2.5A, Charge/Discharge Regulator for Supercapacitor Backup Applications Benefits and Features General Description • • • • • • • • The MAX38886 is a storage capacitor or capacitor bank backup regulator designed to efficiently transfer power between a storage element and a system supply rail in reversible buck and boost operations using the same inductor. When the main supply is present and above the minimum system supply voltage, the regulator operates in buck mode and charges the storage element at up to 500mA peak inductor current. Once the storage element is charged, the circuit draws only 2.5μA of current while it maintains the supercapacitor or other storage element in its ready state. When the main supply is removed, the regulator operates in boost mode and prevents the system from dropping below the minimum operating voltage, discharging the storage element at up to 2.5A peak inductor current. 2.5V to 5V System Output Voltage Up to 4.5V Capacitor Voltage Range Up to 2.5A Peak Inductor Discharge Current Programmable Voltage and Current Thresholds ±2% Threshold Accuracy Up to 95% Efficiency, Charge or Discharge 2.5μA Ready Quiescent Current Small Solution Size • 3mm x 3mm x 0.75mm TDFN Package Ordering Information appears at the end of data sheet. The MAX38886 is externally programmable for minimum and maximum voltage of the storage element, such as supercapacitor, minimum system voltage, and maximum charge and discharge currents. The internal DC-DC converter requires only a 1μH inductor. Applications • • • Handheld Industrial Equipment Portable Computers Portable Devices with a Removable Battery Simplified Block Diagram CHARGE DISCHARGE L1 1µH VSC 2.7V (MAX) CAP + 10F SUPER CAP C2 22µF LX SYS RSTOP 2.49MΩ MAX38886 C1 22µF CAPS RCTOP 2.1MΩ FBS FBCH ENABLE EN GND ISET RCBOT 499kΩ www.maximintegrated.com RISET 20kΩ 19-100855; Rev 1; 8/20 RSBOT 499kΩ VSYS SYSTEM LOAD 3V (MIN) MAIN BATTERY (REMOVABLE) MAX38886 2.5V to 5.0V, 0.5A/2.5A, Charge/Discharge Regulator for Supercapacitor Backup Applications Absolute Maximum Ratings CAP, EN, SYS, LX to GND ................................... -0.3V to +6V Output Short-Circuit Duration ..................................Continuous FBCH to GND ............................................ -0.3V to CAP +0.3V Operating Temperature Range........................-40ºC to +125ºC FBS, ISET to GND ..................................... -0.3V to SYS +0.3V Storage Temperature Range ...........................-65ºC to +150ºC PGND to GND .................................................... -0.3V to +0.3V Maximum Junction Temperature ................................... +150ºC LX RMS Current ........................................................ +2.0ARMS Lead Temperature (Soldering,10 seconds) ................... +300ºC Continuous Power Dissipation (TA = +70°C, TDFN, derate 24.4mW/°C above +70°C) ....................................... 1951.2mW 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 beyond 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. Package Information Package Code T1433+2C Outline Number 21-0137 Land Pattern Number 90-0063 Thermal Resistance, Four-Layer Board: Junction-to-Ambient (θJA) 41°C/W Junction-to-Case Thermal Resistance (θJC) 8°C/W For the latest package outline information and land patterns (footprints), go to https://www.maximintegrated.com/en/design/packaging.html. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermaltutorial. Electrical Characteristics (VSYS = 3.7V, VCAP = 2.7V, Typical values are at TJ = -40ºC to +125ºC, unless otherwise specified.) PARAMETER SYMBOL SYS Voltage Range VSYS CAP Voltage VCAP Min CAP Voltage VCAP SYS Shutdown Current ISYS_SD SYS Charging Supply Current ISYS_CHG SYS Backup Supply Current ISYS_BUP SYS Ready Supply Current ISYS_RDY CAP Shutdown Current ICAP_SD www.maximintegrated.com CONDITIONS MIN TYP 2.5 MAX UNITS 5 V 4.5 V 0.5 EN = 0V, TA = +25ºC 0.01 EN = 0V 0.1 VFBS = 0.6V, VFBCH = 0.485V 1.5 VFBS = VFBCH = 0.515V, TA = +25°C 35 VFBS = VFBCH = 0.515V 35 VFBS = 0.6V, VFBCH = 0.515V, TA = +25°C 2.5 VFBS = 0.6V, VFBCH = 0.515V 2.5 EN = 0V, TA= +25ºC 0.01 V 1 µA mA 65 5 1 µA µA µA Maxim Integrated | 2 MAX38886 2.5V to 5.0V, 0.5A/2.5A, Charge/Discharge Regulator for Supercapacitor Backup Applications (VSYS = 3.7V, VCAP = 2.7V, Typical values are at TJ = -40ºC to +125ºC, unless otherwise specified.) PARAMETER SYMBOL CONDITIONS MIN EN = 0V UVLO Threshold FBS Backup Voltage FBS Charging Threshold FBCH Threshold EN Threshold ISET Resistor Range VUVLOF VFBS VTH_FBS_CHG VTH_FBCH ICHG FBS/FBCH Input Bias Current IFBS/FBCH EN Input Leakage Current IEN LX Switching Frequency fSW LX Leakage Current 1.9 V FBS rising, when discharging stops -2% 0.5 +2% V 25 60 95 mV -2% 0.5 2% V 225 600 Above FBS backup voltage, when charging begins, 30mV typical hysteresis FBCH rising, when charging stops, 25mV typical hysteresis EN rising LX Peak Charge Current Limit (Note 1) LX Low-Side FET Resistance LX High-Side FET Resistance 1.8 VIH IDCHG UNITS 1.7 When LX stops switching, EN falling LX Peak Backup Current Limit (Note 1) MAX 0.1 VVSYS falling, 100mV typical hysteresis VIL RISET TYP Guaranteed by LX peak current limits Circuit of Figure 1, VCAP = 2V, VSYS = 2.9V, RISET = 20kΩ Circuit of Figure 1, VCAP = 2V, VSYS = 2.9V, RISET = 100kΩ Circuit of Figure 1, VSYS = 3.7V, VCAP = 2V, RISET = 20kΩ Circuit of Figure 1, VSYS =3.7 V, VCAP = 2V, RISET = 100kΩ VFBS/FBCH = 0.5V, TA = +25°C 660 20 2.0 100 2.5 mV kΩ 3.0 A 0.5 400 500 600 mA 100 -0.1 VFBS/FBCH = 0.5V 0V < VEN < 5.5V, TA = +25°C 925 0.001 0.1 0.01 -0.1 0V < VEN < 5.5V 0.001 0.1 0.01 µA µA Delivering maximum current from CAP 2 RLOW VSYS = 3V, LX switched to GND 50 100 mΩ RHIGH VSYS = 3V, LX switched to SYS 80 160 mΩ ILX_LKG VEN = 0V, VSYS = 5V, VLX = 0V/5V, TA = +25°C -1 VEN = 0V, VSYS = 5V, VLX = 0V/5V MHz 1 µA 0.1 Maximum On-Time tON Backup mode, VFBS = 0.485V 320 400 480 ns Minimum Off-Time tOFF Backup mode, VFBS = 0.485V 80 100 120 ns Overtemperature Lockout Threshold High-Side FET Zero-Crossing (Note 1) Low-Side FET Zero-Crossing (Note 1) TOTLO IZXP IZXN TJ rising, 15°C typical hysteresis Circuit of Figure 1, VCAP = 2V, VSYS = 2.9V Circuit of Figure 1, VSYS = 3.7V, VCAP = 2V 165 °C 25 50 75 mA 25 50 75 mA Note 1: DC measurement, actual zero-crossing and peak current accuracy in circuit will be affected by the propagation delay time. Note 2: Limits over the specified operating temperature and supply voltage range are guaranteed by design and characterization, and production tested at TJ = +25ºC only. www.maximintegrated.com Maxim Integrated | 3 MAX38886 2.5V to 5.0V, 0.5A/2.5A, Charge/Discharge Regulator for Supercapacitor Backup Applications Typical Operating Characteristics (MAX38886, VSYS = 3.6V, VCAP = 2.0V, C1 = 22µF, C2 = 22µF, TA = +25°C, unless otherwise noted.) www.maximintegrated.com Maxim Integrated | 4 MAX38886 www.maximintegrated.com 2.5V to 5.0V, 0.5A/2.5A, Charge/Discharge Regulator for Supercapacitor Backup Applications Maxim Integrated | 5 MAX38886 2.5V to 5.0V, 0.5A/2.5A, Charge/Discharge Regulator for Supercapacitor Backup Applications FBCH CAPS 9 8 11 CAP 10 EN 12 LX 13 N.C. TOP VIEW 14 PGND Pin Configurations MAX38886 EXPOSED PAD 5 7 GND 4 N.C. 6 3 N.C. FBS 2 N.C. ISET 1 SYS + TDFN-EP 3mm x 3mm Pin Descriptions PIN NAME FUNCTION 1 SYS System Supply Rail. Connect to a system supply rail or removable battery between 2.5V and 5V and bypass with a 22μF capacitor to GND. 2 NC No Connect 3 NC No Connect 4 NC No Connect 5 ISET 6 FBS 7 GND Analog Ground 8 CAPS CAP Sense Input. Connect to CAP pin. 9 FBCH CAP Feedback Input. Connect to the lower point of a resistor-divider from CAP to GND. www.maximintegrated.com Charge/Discharge Current Select Input. The peak discharge current is set by 50kV/RISET while the peak charging current is 1/5 the discharging current. SYS Feedback Input. Connect to the center point of a resistor divider from SYS to GND. SYS will boost to 0.5V x (1 + RSTOP/RSBOT) when VFBS < 0.5V. Maxim Integrated | 6 MAX38886 2.5V to 5.0V, 0.5A/2.5A, Charge/Discharge Regulator for Supercapacitor Backup Applications CAP will charge to 0.5V x (1 + RCTOP/RCBOT) when VFBS > 0.56V. Enable Input. Force this pin high to enable the regulator or force pin low to disable the part and enter shutdown. If not driven, tie it to the SYS rail. 10 EN 11 CAP 12 LX Inductor Switching Node. Connect a 1.0μH to 4.7μH inductor from LX to CAP. 13 NC No Connect 14, EP PGND Super Cap. Connect to a supercapacitor input. Power Ground Functional Diagram CAP SYS BIAS EN LX DRIVERS CONTROL ISET PGND MAX38886 FBS MODE SELECT FBCH CAPS GND www.maximintegrated.com Maxim Integrated | 7 MAX38886 2.5V to 5.0V, 0.5A/2.5A, Charge/Discharge Regulator for Supercapacitor Backup Applications Detailed Description The MAX38886 is a flexible storage capacitor or capacitor bank backup regulator that efficiently transfers power between a storage element and a system supply rail. When the main supply is present and its voltage above the minimum system supply voltage, the regulator operates in the charging mode of operation and charges the storage element at up to 500mA peak inductor current. When the main supply is removed, the regulator prevents the system from dropping below the minimum operating voltage, boosting VSYS by discharging the storage element at up to 2.5A peak inductor current. For backup mode functioning, ensure that the supercapacitor is charged up to 2.7V. During this backup mode of operation, the MAX38886 utilizes a fixed on-time, current-limited, pulse-frequency-modulation (PFM) control scheme. When VSYS is applied for the first time, ensure that the supercapacitor is charged to 2.7V to activate backup mode. The external pins allow a wide range of system and storage element, such as supercapacitor voltage settings, as well as charging and discharging peak inductor current settings. The MAX38886 implements a True Shutdown™ feature disconnecting VSYS from VCAP, as well as protecting against a SYS short or if VCAP > VSYS. Application Circuit The typical application of the MAX38886 is shown in Figure 1. Supercapacitor Voltage Configuration The maximum supercapacitor voltage is set using a resistor-divider from CAP to FBCH to GND. The recommended value for RCBOT is 499kΩ. Because resistor tolerance has a direct effect on voltage accuracy, these resistors should have 1% accuracy or better. RCTOP = RCBOT x ((VCAPMAX/0.5) - 1) VCAP halts charging when VFBCH reaches 0.5V. The maximum supercapacitor voltage is where the supercapacitor remains after it is completely charged. The supercapacitor supports backup until the voltage across it reaches 500mV (typ). The duty cycle limitation of the boosting phase is 80% (typ). The MAX38886 detects when VSYS falls below VCAP. The device will not enable if VSYS is below VCAP. Raising VSYS above the backup threshold re-initiates charging and backup. System Voltage Configuration The minimum system voltage is set using a resistor-divider from SYS to FBS to GND. Recommended value for RSBOT is 499kΩ. Because resistor tolerance has a direct effect on voltage accuracy, these resistors should have 1% accuracy or better. RSTOP = RSBOT x ((VSYSMIN/0.56) - 1) When VFBS is above 0.56V, the DC-DC regulator draws power from the SYS pin to charge the supercapacitor to the maximum voltage set by FBCH and be ready for backup. When the main battery is removed, VFBS drops to 0.5V and the SYS pin is regulated to the programmed minimum voltage with up to 2A of CAP current. Charge/Discharge Current Configuration The peak inductor discharge current is set by placing a resistor from ISET to GND. The values of RISET resistor is calculated by following formula: IDISCHARGE = 2.5A x (20kΩ/RISET) The supercapacitor charging current is internally set to 1/5 of the discharge current. ICHARGE = 0.5A x (20kΩ/RISET) A value of RISET between 20kΩ and 100kΩ is recommended to ensure accurate current compliance. www.maximintegrated.com Maxim Integrated | 8 MAX38886 2.5V to 5.0V, 0.5A/2.5A, Charge/Discharge Regulator for Supercapacitor Backup Applications Typical Application Circuits CHARGE DISCHARGE L1 1µH VSC 2.7V (MAX) CAP + 10F SUPER CAP C2 22µF LX SYS RSTOP 2.49MΩ MAX38886 C1 22µF VSYS SYSTEM LOAD 3V (MIN) MAIN BATTERY (REMOVABLE) CAPS RCTOP 2.1MΩ FBS FBCH ENABLE EN GND RCBOT 499kΩ ISET RISET 20kΩ RSBOT 499kΩ Figure 1. Typical Application VOLTAGE (V) 4 VSYS 3.36 VSYS REGULATED 3.18 3 2.7 VCAP LOW IQ 0.5 (TYP) 0 CHARGING CAP (BUCK) IDLE (NO SWITCHING) BACK-UP (BOOST) Figure 2. Charging/Discharging Waveforms www.maximintegrated.com Maxim Integrated | 9 MAX38886 2.5V to 5.0V, 0.5A/2.5A, Charge/Discharge Regulator for Supercapacitor Backup Applications Applications Information Capacitor Selection Capacitors at SYS and CAP pins reduce current peaks and increase efficiency. Ceramic capacitors are recommended because they have the lowest equivalent series resistance (ESR), smallest size, and lowest cost. Choose an acceptable dielectric such as X5R or X7R. Due to ceramic capacitors' capacitance derating with DC bias standard 22µF ceramic capacitors are recommended at both pins for most applications. Supercapacitor Selection When the power source supplying the VSYS voltage is removed, power to the output is provided by the MAX38886 operating in the backup or boost mode of operation using the supercapacitor as its source. In order to ensure the supply voltage stays in regulation, the amount of power the supercapacitor can deliver at its minimal voltage should be greater than that required by the system. The MAX38886 presents a constant power load to the supercapacitor where smaller current is pulled out of the supercapacitor near its maximum VCAP voltage. However, current drawn from the supercapacitor increases as it discharges to maintain constant power at the load. The amount of energy required in the backup mode is the product of the constant backup power and time defined as backup time, t BACKUP. The amount of energy available in the supercapacitor is calculated using the following formula: E = 1/2 x CSCAP x (VCAPMAX2 – VCAPMIN2) (J) The amount of energy required to complete the backup equals to: E = VSYS x ISYS x tBACKUP (J) where, ISYS will be the system load during backup. Since energy required at the system side during the backup event comes from available energy in the supercapacitor, and assuming conversion efficiency η, and given tBACKUP, the required CSCAP is determined by the following equation: CSCAP = (2 x VSYS x ISYS x tBACKUP) / [(VCAPMAX2 – VCAPMIN2) x η] (F) For example, in Figure 1 (Application Circuit), the minimum value of the supercapacitor required for 1s backup time, assuming 200mA system load and average efficiency of 93%, is calculated as: CSCAP ≥ (2 x 3.0V x 0.2A x 1s) / [((2.7V)2 – (1.5V)2) x 0.93] = 256mF Note: VCAPMIN should be selected such that it supplies the load current to target the SYS voltage. The supercapacitor will continue to discharge till 0.5V (typ). Inductor Selection The MAX38886 works with a 1µH inductor in most applications. In applications where lower peak currents are desired, larger inductance may be used in order to reduce the ripple. The recommended inductance range is from 1µH to 4.7µH. L (µH) 1 to 1.5 2.2 3.3 4.7 RISET (kΩ) 20 to 30 30 to 45 45 to 70 70 to 100 Enabling Device The MAX38886 has a dedicated enable pin. The pin can either be driven by a digital signal or pulled up or strapped to the SYS rail. PCB Layout Guidelines Minimize trace lengths to reduce parasitic capacitance, inductance and resistance, and radiated noise. Keep the main power path from SYS, LX, CAP, and PGND as tight and short as possible. Minimize the surface area used for LX since this is the noisiest node. The trace between the feedback resistor-dividers should be as short as possible and isolated www.maximintegrated.com Maxim Integrated | 10 MAX38886 2.5V to 5.0V, 0.5A/2.5A, Charge/Discharge Regulator for Supercapacitor Backup Applications from the noisy power path. Refer to the EV kit layout for best practices. The PCB layout is important for robust thermal design. The junction to ambient thermal resistance of the package greatly depends on the PCB type, layout, and pad connections. Using thick PCB copper and having the SYS, LX, CAP, and PGND copper pours will enhance the thermal performance. The TDFN package has a large thermal pad under the package, which creates excellent thermal path to PCB. This pad is electrically connected to PGND. Its PCB pad should have multiple thermal vias connecting the pad to the internal PGND plane. Thermal vias should either be capped or have a small diameter to minimize solder wicking and voids. Ordering Information PART NUMBER MAX38886ATD+ www.maximintegrated.com TEMP RANGE -40°C to +125°C PIN-PACKAGE 14 TDFN FEATURES Enable input; selectable voltage and currents Maxim Integrated | 11 MAX38886 2.5V to 5.0V, 0.5A/2.5A, Charge/Discharge Regulator for Supercapacitor Backup Applications Revision History REVISION NUMBER 0 1 REVISION DATE 6/20 8/20 DESCRIPTION Initial release Release for intro PAGES CHANGED — 7 For pricing, delivery, and ordering information, please visit Maxim Integrated’s online storefront at https://www.maximintegrated.com/en/storefront/storefront.html. Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. © 2020 Maxim Integrated Products, Inc.