Click here for production status of specific part numbers. Evaluates: MAX38888 MAX38888 Evaluation Kit General Description Quick Start The MAX38888 evaluation kit (EV kit) evaluates the Required Equipment MAX38888 IC. The MAX38888 is a super cap backup MAX38888 EV kit regulator designed to transfer power between a super cap 5V, 3A DC power supply and a system supply rail. When the main battery is present and above the minimum system supply voltage, the One digital multimeter (DMM) regulator charges the super cap at up to a 500mA rate. Procedure Once the super cap is charged, the circuit draws only The EV kit is fully assembled and tested. Follow the steps 2.5A of current while it maintains the super cap in its below to verify board operation. Caution: Do not turn ready state. When the main battery is removed, the on power supply until all connections are completed. regulator prevents the system from dropping below the minimum operating voltage, discharging the super 1) Verify that a shunt is installed onto pins 1 and 2 cap at up to a 2.5A rate. The MAX38888 is externally jumper JU1 (EV kit enabled). programmable for minimum and maximum super cap 2) Verify that jumper JU2 is opened (No load is connect- voltage, minimum system voltage, and maximum charge ed across VSYS and PGND). and discharge currents. The internal DC/DC converter 3) Set the power supply output to 3.4V and disable the requires only a 1H inductor. power supply. Features 4) Connect the power supply between the VSYS and PGND terminal posts. 2.99V to 3.36V System Output Voltage Range 5) Connect the DMM between the VSC and PGND 1.42V to 2.71V Super Cap Voltage Range terminal posts. 2.5A Peak Discharge Current 6) Enable the power supply and verify that super cap Resistor Adjustable Voltage and Current Thresholds voltage at VSC is ramping up and stops at about 2.7V. Proven 2-Layer 2oz Copper PCB Layout 7) Disable and disconnect the power supply from the Demonstrates Compact Solution Size VSYS and PGND terminal posts. Fully Assemble and Tested 8) Verify that VSYS drops to about 3V, and VSC drops to about 2.5V. 9) Install jumper JU2 (This connects a 51 load across MAX38888 EV Kit Files VSYS and PGND). FILE DECRIPTION 10) Verify that VSYS remains at 3V while VSC is ramping down toward 1.5V. MAX38888 EV BOM EV Kit Bill of Material 11) Verify that VSYS is 0V when VSC drops below 1.5V. MAX38888 EV PCB Layout EV Kit Layout MAX38888 EV Schematic EV Kit Schematic Ordering Information appears at end of data sheet. 319-100243 Rev 1 7/19Evaluates: MAX38888 MAX38888 Evaluation Kit Ready Mode Detailed Description of Hardware Once the super cap is charged to its maximum voltage, The MAX38888 EV kit provides a flexible circuit to evaluate the super cap backup regulator. External 2.7V, the circuit draws only 2.5A of current while it main- tains the super cap in its ready state. The MAX38888 EV components allow a wide range of system and super cap voltages as well as charging and discharging currents. Kit maximum super cap voltage is set to 2.7V, by resistors R1, R2, and R3 with V = 0.5V, FBCH EN Discharge Mode The MAX38888 EV kit provides a jumper (JU1) to enable When the main battery is removed, the regulator or disable the MAX38888. Refer to Table 1 for JU1 jumper settings. discharges the super cap at up to a 2.5A rate to prevent the system from dropping below the minimum operat- VSYS Load ing voltage. The MAX38888 EV kit minimum operating The MAX38888 EV kit provides a jumper (JU2) to connect voltage is set to 2.99V, by resistors R5 and R6 with a 51 resistive load across VSYS and PGND to simulate V = 0.5V. FBS a discharging scenario during test. Refer to Table 2 for Preserve Mode JU2 jumper settings. As the super cap is discharged toward its minimum Charge Mode voltage, 1.42V, the MAX38888 disconnects all circuitry When the main battery is present and is above the from the super cap and draws only 2.5A of current to minimum system supply voltage, the regulator charges preserve the remaining capacity for keeping alive the the super cap at up to a 500mA rate. The MAX38888 EV real-time clock, memory, or other low-level function. The Kit minimum system supply voltage is set to 3.36V, by MAX38888 EV Kit minimum super cap voltage is set to resistors R5 and R6 with V = 0.56V. FBS 1.42V, by resistors R1, R2, and R3 with V = 0.475V. FBCL Table 1. EN (JU1) Charge/Discharge Current Configuration The MAX38888 EV Kit provides a resistor R4 to configure JU1 DESCRIPTION the charge/discharge current rate for the super cap. SHUNT POSITION The peak discharge current is set by resistor R4 connect- 1-2* Enabled. EN = VSYS ing between the ISET and GND pins. 2-3 Disabled. EN = PGND I = 2.5A x (20k/R4) DISCHARGE Enabled. EN = VSYS Not Installed The super cap charging current is internally set to 1/5 of (through resistor R9) the discharge current. *Default position. I = 0.5A x (20k/R4) CHARGE Table 2. VSYS Load (JU2) Choose a value of R4 between 20k to 100k to ensure accurate current compliance. JU2 DESCRIPTION SHUNT POSITION Test Mode: A 51 resistive load is Installed connected across VSYS and PGND Not Installed* Normal Operating Mode *Default position. Maxim Integrated 2 www.maximintegrated.com