DEMO MANUAL DC2220A LTC3643 Bidirectional Charger/Regulator for System Power Backup DESCRIPTION Demonstration circuit 2220A is a 2A, bidirectional charger/ Demo circuit 2220A is set up for automatic mode opera- regulator featuring the LTC 3643, a bidirectional synchro- tion. In this mode, the DC2220 automatically charges the nous step-up charger and step-down converter. DC2220A energy storage capacitor when a system voltage is present. implements backup by charging a storage capacitor up to It automatically switches to work as a step-down DC/DC 40V in boost mode, when the input voltage is present. It converter providing system backup power to the load when discharges the storage capacitor in buck mode, providing system power is removed. An on board MOSFET isolates a regulated load voltage of 3V to 17V (set to 5V), when the backup circuit from the input line if the system voltage the input is interrupted. Its wide voltage range, both in is not present, implementing PowerPath functionality. capacitor charger mode and in system backup mode, The DC2220A supports three levels of load current limits: makes it well suited to a wide variety of applications. The 2A, 3A and 4A when working as step-down converter ability of the LTC3643 to boost an input rail to a relatively discharging the energy storage capacitor. high voltage of 40V, combined with the DC2220 option of The DC2220A has a small circuit footprint. It is a high adding external capacitor banks, makes this regulator an performance and cost effective solution for high voltage excellent choice for energy storage applications. capacitor backup converters, servers, solid-state drives, The DC2220A features automatic switching from charge RAID and RF systems. to backup mode, 2A input current limit during charging, The LTC3643 s input disconnect circuitry protects the the ability to set maximum current in the backup mode of DC2220A from short circuit and overcurrent conditions operation, Burst Mode operation, fast 1MHz switching in the boost mode of operation, in case a short circuit oc- frequency, and open-collector outputs to indicate charge curs on a high voltage rail. A similar circuit protects the status and input power fail. DC2220A against a short circuit in step-down mode, when The 1MHz constant-frequency operation results in a small the load is supplied from an energy storage capacitor. and efficient circuit. In backup mode, the LTC3643 provides Design files for this circuit board are available at high output voltage accuracy over a wide load range with GND VIN DEMO MANUAL DC2220A QUICK START PROCEDURE Demonstration circuit 2220A is easy to set up to evaluate To verify the capability of the DC2220A for charging energy the performance of the LTC3643 bidirectional regulator. storage capacitors, proceed with the following steps: Refer to Figure 1 for the proper measurement equipment 1. Place jumper RUN (JP1) to OFF position. setup and follow the procedure below. 2. Place jumper ILIM BUCK (JP2) to 2.0A position. NOTE: When measuring the input or output voltage ripple, 3. With power off, connect the input power supply to care must be taken to avoid a long ground lead on the terminals V (E1) and GND, voltmeter to V (E8) oscilloscope probe. Measure the input or output voltage IN CAP and GND, load to LOAD (E3) and GND as shown on ripple by touching the probe tip directly across the V or IN Figure1. V and GND terminals. See Figure 2 for proper scope OUT probe technique. 20V POWER SUPPLY + + + LOAD Figure1. Proper Measurement Equipment Setup Figure2. Measuring Input or Output Ripple dc2220afb 2