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Linear Technology DC2118A Demo Manual

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DESCRIPTION
Demonstration circuit 2118A is a combination step-down
battery charger and step-up battery backup regulator us-
ing the
LTC
4040
®
DC2118A has an input voltage range from 4.8V to 5.5V
with overvoltage protection (OVP) to 40V, as limited by
the external MOSFET. The input current is monitored to
prioritize the load up to the 2.5A threshold before charge
current is reduced.
Battery Charging
As initially configured, DC2118A is programmed for 2A
charge current limit when in charge mode. The charge
voltage is jumper-selectable in 8 discrete steps from
3.45V to 3.6V for LiFePO
Li-ion chemistry, according to the F2/F1/F0 programming
input settings.
The charge current limit is adjustable via the PROG pin
resistor. End-of-charge status is triggered by current
falling below C/8 and indicated by the CHRG LED. The
optional NTC input provides temperature fault detection
PERFORMANCE SUMMARY
PARAMETER
Charge Mode
Input Voltage Range
Overvoltage Protection Range
Input Current Limit
Default Charging Voltage
Charging Current
Safety Timer Period
Backup Mode
DCIN Input Power Fail Threshold
System Output Voltage
Backup Battery Voltage Range
System Reset Threshold
Backup Boost Efficiency
Arrow.com.
Downloaded from
monolithic system power manager. The
chemistry or 3.95V to 4.1V for
4
DEMO MANUAL DC2118A
Battery Charger and Backup
and status indicated by the FAULT LED. Charging can be
enabled/disabled with the ENCHG jumper.
Battery Backup
Following an input power failure, the circuit automatically
shifts to battery backup boost mode to regulate the VSYS
output rail. The backup mode system output voltage is
initially programmed for 5V. The input power failure status
is indicated by the PFO LED.
If VSYS ever falls below the programmed reset threshold
voltage, the RST LED will change states to indicate the
need to reset the system and recharge the battery. Backup
regulation can be enabled/disabled with the ENBST jumper.
For convenience, all LEDs can be disabled with the LED
jumper to reduce the quiescent current of the system.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2118A
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Specifications are at T
= 25°C
A
CONDITIONS
Limited by Q1 BV
DSS
R7 = 10mΩ
F2 = 1 (Li-Ion), F1 = 1, F0 = 1
RPROG = 1.00k
F2 = 1 (Li-Ion)
F2 = 0 (LiFePO
)
4
R2 = 357k, R27 = 121k, DCIN Falling
R4 = 1.69M, R5 = 324k
R4 = 1.69M, R5 = 324k, VSYS Falling
VBAT = 3.6V, ISYS = 2A, VOUT = 5V
LTC4040
Power Manager
4.8V to 5.5V
2.7V to 5.0V
VALUE
5.5V to 40V
2.5A
4.10V
2.0A
4Hr
2Hr
4.8V
5.0V
4.6V
89%
dc2118af
1

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Summary of Contents for Linear Technology DC2118A

  • Page 1 End-of-charge status is triggered by current falling below C/8 and indicated by the CHRG LED. The L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.

  • Page 2: Performance Summary

    QUICK START PROCEDURE Demonstration circuit 2118A is easy to set up to evaluate NOTE: While DC2118A is robust to overvoltage condi- the performance of LTC4040. Refer to Figure 2 for proper tions up to 40V on DCIN, DO NOT exceed this limit or measurement equipment setup and follow the procedure damage may occur to MOSFET Q1 and IC U1.
  • Page 3 DEMO MANUAL DC2118A QUICK START PROCEDURE 11. Total backup runtime is based on battery capacity, 2000 • V PROG circuit efficiency, and system load. Figure 2 shows an PROG example discharge curve with constant current system load. Where R = R6 = 1kΩ.

  • Page 4: Parts List

    DEMO MANUAL DC2118A PARTS LIST ITEM REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Required Circuit Components CIN1 CAP., X7R, 0.1µF, 10%, 50V, 0805 AVX, 08055C104KAT4A COUT1, COUT2 CAP., X5R, 100µF, 20%, 10V, 1210 MURATA, GRM32ER61A107ME20L CAP., X7R, 2.2µF, 10%, 6.3V, 0805 MURATA, GRM21BR70J225MA01L CAP., X5R, 10µF, 20%, 10V, 0603...

  • Page 5: Schematic Diagram

    Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
  • Page 6 Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions: This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety measures typically found in finished commercial goods.

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