DC2220A Datasheet DC2220A | P1-P3

dc2220afb

DEMO MANUAL DC2220A

DESCRIPTION

LTC3643

Bidirectional Charger/Regulator for

System Power Backup

Demonstration circuit 2220A is a 2A, bidirectional charger/

regulator featuring the LT C

3643, a bidirectional synchro-

nous step-up charger and step-down converter. DC2220A

implements backup by charging a storage capacitor up to

40V in boost mode, when the input voltage is present. It

discharges the storage capacitor in buck mode, providing

a regulated load voltage of 3V to 17V (set to 5V), when

the input is interrupted. Its wide voltage range, both in

capacitor charger mode and in system backup mode,

makes it well suited to a wide variety of applications. The

ability of the LTC3643 to boost an input rail to a relatively

high voltage of 40V, combined with the DC2220 option of

adding external capacitor banks, makes this regulator an

excellent choice for energy storage applications.

The DC2220A features automatic switching from charge

to backup mode, 2A input current limit during charging,

the ability to set maximum current in the backup mode of

operation, Burst Mode

operation, fast 1MHz switching

frequency, and open-collector outputs to indicate charge

status and input power fail.

The 1MHz constant-frequency operation results in a small

and efficient circuit. In backup mode, the LTC3643 provides

high output voltage accuracy over a wide load range with

no minimum load requirement.

PERFORMANCE SUMMARY

Demo circuit 2220A is set up for automatic mode opera-

tion. In this mode, the DC2220 automatically charges the

energy storage capacitor when a system voltage is present.

It automatically switches to work as a step-down DC/DC

converter providing system backup power to the load when

system power is removed. An on board MOSFET isolates

the backup circuit from the input line if the system voltage

is not present, implementing PowerPath™ functionality.

The DC2220A supports three levels of load current limits:

2A, 3A and 4A when working as step-down converter

discharging the energy storage capacitor.

The DC2220A has a small circuit footprint. It is a high

performance and cost effective solution for high voltage

capacitor backup converters, servers, solid-state drives,

RAID and RF systems.

The LTC3643's input disconnect circuitry protects the

DC2220A from short circuit and overcurrent conditions

in the boost mode of operation, in case a short circuit oc-

curs on a high voltage rail. A similar circuit protects the

DC2220A against a short circuit in step-down mode, when

the load is supplied from an energy storage capacitor.

Design files for this circuit board are available at

http://www.linear.com/demo/DC2220A

L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks

and PowerPath is a trademark of Linear Technology Corporation. All other trademarks are the

property of their respective owners.

Specifications are at T

= 25°C

PARAMETER CONDITIONS UNITS

Minimum Input Supply Voltage 3.0 V

Maximum Input Supply Voltage 17.0 V

System Voltage Range Backup (Step-Down) Mode 3.0 to 17.0 V

Energy Storage Capacitor Voltage Range 3.0V to 40V V

Typical Switching Frequency 1.0 MHz

Efficiency Typical, Backup Mode V

CAP

= 12V, V

LOAD

= 5.0V, I

LOAD

= 0.5A 93 %

dc2220afb

DEMO MANUAL DC2220A

QUICK START PROCEDURE

Demonstration circuit 2220A is easy to set up to evaluate

the performance of the LTC3643 bidirectional regulator.

Refer to Figure 1 for the proper measurement equipment

setup and follow the procedure below.

NOTE: When measuring the input or output voltage ripple,

care must be taken to avoid a long ground lead on the

oscilloscope probe. Measure the input or output voltage

ripple by touching the probe tip directly across the V

OUT

and GND terminals. See Figure 2 for proper scope

probe technique.

To verify the capability of the DC2220A for charging energy

storage capacitors, proceed with the following steps:

. Place jumper RUN (JP1) to OFF position.

. Place jumper ILIM_BUCK (JP2) to 2.0A position.

. With power off, connect the input power supply to

terminals V

(E1) and GND, voltmeter to V

CAP

(E8)

and GND, load to LOAD (E3) and GND as shown on

Figure1.

Figure1. Proper Measurement Equipment Setup

20V

POWER

SUPPLY

LOAD

–

GND

VIN

Figure2. Measuring Input or Output Ripple

dc2220afb

DEMO MANUAL DC2220A

QUICK START PROCEDURE

4. Turn the input power source on and slowly increase

the input voltage to 5.5V. Set the load to 0.1A. You

have to see voltage around 4.8V on terminal LOAD,

a diode forward voltage drop lower compared to V

If there is no output, temporarily disconnect the load

to make sure that the load is not set too high.

. Place jumper RUN (JP1) in the ON position. Voltage

on V

CAP

terminal should rise to 39V level. Voltage on

terminal LOAD should be equal to input voltage.

To verify the ability of DC2220 to work in backup mode,

proceed with the following:

. Disconnect input power from V

terminal; energy

storage capacitor C5 starts discharging from 39V level,

however LTC3643 will maintain a voltage of 5.0V on

terminal LOAD.

. To increase holdup time, install optional capacitor C6

on the bottom side of DC2220A or connect additional

capacitor bank to terminals V

CAP

(E8) and GND (E7).

200µs/DIV

1V/DIV

DC2220 F03a

LOAD

50ms/DIV

1V/DIV

DC2220 F03b

LOAD

LOAD CURRENT (A)

EFFICIENCY (%)

DC2220 F04

0 2.5 321 1.50.5

Figure3. Power interruption, V

LOAD

5.0V, I

LOAD

0.5A

Figure4. Efficiency vs Load, V

CAP

12V, LOAD 5.0V, Step-Down Mode

8. Repeat steps 1 to 7 for different load currents and V

voltages.

. You can measure voltage regulation and ripple in

backup mode on V

LOAD

terminals.

. Make sure that input voltage on V

terminals does not

exceed 17V and V

CAP

voltage is not set above 40V.

Figure 3 illustrates power interruption. In the beginning of

the process V

(yellow) is 5.5V and supplies LOAD rail,

PFI signal is low and step-down converter is OFF. Once

value is reduced to 4.75V, PFI signal changes state

to high, the step-down converter turns ON and starts to

supply the LOAD rail by 5.0V taking energy from the storage

capacitor C5. The efficiency curve is presented in Figure 4.

The efficiency measurement was conducted in step-down

mode. A constant DC voltage of 12V was applied to the V

CAP

and GND terminals with the input voltage disconnected

from the V

and GND terminals.

P1-P3 P4-P6

DC2220A

Mfr. #:

Buy DC2220A

Manufacturer:

Analog Devices Inc.

Description:

Power Management IC Development Tools LTC3643 Demo Board - 2A, Bidirectional C

Lifecycle:

New from this manufacturer.

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