Application Note
EnerChip™ CC Li-Ion Battery Charger with Integrated Energy Storage
Power Manager with Charge Control
Capable of Charging Li-Ion Coin Cells
Integrated Thin Film Energy Storage
Built-in Energy Storage Protection
Temperature Compensated Charge Voltage
Operates Over a Wide Power Supply Range
Low Standby Power and Cutoff Current
Integrated Energy Storage: Low Self-Discharge
and Thousands of Recharge Cycles Available
• Eco-Friendly, RoHS Compliant
• Surface Mount - Lead-Free Reflow Tolerant
• Standby supply for non-volatile SRAM, real-time
clocks, controllers, and supply supervisors.
• Wireless sensors and RFID tags and other
powered, low duty cycle applications.
• Localized power source to keep microcontrollers
and other devices alert in standby mode.
• Power bridging to provide back-up power to the
system during exchange of main batteries.
• Consumer appliances that have real-time
• Business and industrial systems such as
network routers, point-of-sale terminals, test
equipment, printers, and industrial controllers.
• Energy Harvesting by coupling the EnerChip
with energy transducers such as solar panels.
EnerChip CC: Battery Management
with Integrated Energy Storage
The EnerChip CC product family consists of
devices having battery management circuitry
and rechargeable solid state energy storage - the
EnerChip - integrated in a single low profile, surface
mount package.
Each device functions as a backup power source
and supervisor for low power applications and has
the added capability to manage the charging and
discharge cutoff of Li-ion batteries such as LiR
coin cells. The EnerChip CC can deliver up to 1mA
charging current at 4.1V. It can charge up to 10
additional EnerChips connected in parallel.
During normal operation, the EnerChip CC derives
power from the main supply (2.5V to 5.5V) that
activates the internal charge pump, producing 4.1V
on the VCHG pin. This voltage not only charges
the internal EnerChips, but can also serve as a
charging source for small rechargeable Li-ion cells.
The EnerChip CC also has a discharge cutoff circuit
(3.0V typical) that prevents the battery from being
discharged too deeply - a condition that can destroy
Li-ion cells. When the primary power supply drops
below a user-defined threshold voltage, the EnerChip
CC monitors this event, routes the battery voltage to
VOUT, and signals the event by driving RESET/ low.
Figure 1: Application Circuit Showing Connection of External Li-Ion Rechargeable Cell.
©2010 Cymbet Corporation • Tel: +1-763-633-1780 •
AN-1041 Rev A
Page 1 of 3
EnerChip CC Li-Ion Battery Charger with Integrated Energy Storage
EnerChip CC Operation
The EnerChip CC schematic is shown in Figure 2. The device is typically configured to operate from a main
supply such as wall power or a large battery, which is applied to VDD and routed to VOUT directly through a
p-channel pass FET to power the system components. When that supply voltage drops below the threshold
voltage as determined by the VMODE comparator setting, the EnerChip CC redirects power to VOUT from the
internal EnerChip. The EnerChip gets charged whenever the charge pump is active. The charge pump can be
disabled by external control of the ENABLE line and will also be disabled anytime VDD drops below 2.5V.
VMODE is an analog input ranging from 0V to VDD. The ENABLE pin is a digital input that turns off the charge
pump when low. Depending on the operating mode, VOUT is supplied from VDD, the integrated EnerChip, or an
external battery attached to VCHG. RESET/ is a digital output that, when low, indicates VOUT is being sourced
by the integrated EnerChip or external battery and not the main power supply connected to VDD.
CFLY is the flying capacitor in the voltage doubler circuit. The value of CFLY can be changed if the output
impedance of the EnerChip CC needs to be modified - for example, when it is necessary to increase the charge
pump drive current to charge a Li-ion battery attached to VCHG. The output impedance is dictated by 1/fC,
where f is the frequency of oscillation (typically 100kHz) and C is the capacitor value (typically 0.1µF). See DS72-03 EnerChip CC CBC3150 Datasheet or DS-72-04 EnerChip CC CBC3112 Datasheet for guidelines on sizing
the charge pump capacitor for your application.
Figure 2: EnerChip CC Internal Block Diagram
Electrical Properties
EnerChip backup output voltage:
Energy storage capacity (typical): Recharge time to 80%:
Charge/discharge cycles: Physical Properties
Operating temperature:
Storage temperature:
12µAh to 50µAh
10 minutes
>5000 to 10% discharge
20-pin dual flat no-lead (DFN)
-20°C to +70°C
-40°C to +125°C
©2010 Cymbet Corporation • Tel: +1-763-633-1780 •
AN-1041 Rev A
Page 2 of 3
EnerChip CC Li-Ion Battery Charger with Integrated Energy Storage
Using Additional EnerChips and External Batteries
The EnerChip CC is designed to permit attachment of additional EnerChips or small rechargeable Li-ion batteries that can be charged with a constant voltage of 4.1V. In cases where the internal EnerChip has insufficient
energy to power the system for extended periods, an external rechargeable Li-ion cell can be attached to the
VCHG pin. VCHG delivers up to 1mA at 4.1V and can therefore charge a small, fully depleted Li-ion coin cell in a
matter of several hours. This configuration allows the designer to achieve longer system run-time than what the
EnerChips can provide, while avoiding the relative bulk associated with non-rechargeable cells.
As configured in the schematic of Figure 1, the circuit will operate from the external Li-ion battery (and internal
EnerChip in parallel) whenever VDD is below 3.0V (typical). The Li-ion cell and EnerChip will be charging whenever ENABLE is at a logical high and VDD is above 2.5V. To isolate the Enerchip from the Li-ion cell, simply do
not connect VCHG to VBAT. VBAT is the positive terminal of the EnerChip within the EnerChip CC package.
The battery discharge cutoff voltage is fixed at 3.0V +/- 0.25V. To ensure the cutoff circuit is applied to the Liion cell, the system load must be powered from VOUT and not directly from the Li-ion cell. VOUT, when sourced
from the EnerChip or external battery, is protected internally by a silicon diode. Consequently, the voltage at
VOUT will be approximately 0.6V below the battery terminal voltage. If the cutoff circuit is not needed, the output can be derived directly from the Li-ion cell, which is tied to VCHG. Charging voltage on VCHG will be disconnected whenever the charge pump is inactive - either by driving the ENABLE pin low, or when the supply voltage
on VDD drops below 2.5V.
Examples of rechargeable batteries supported by EnerChip CC are the LiR-type coin cells, including LiR-1220
(~8mAh) and LiR-2032 (~40mAh). The charging rate for such external cells will be a function of available input
power, to a maximum of 1mA as limited by the EnerChip CC charge pump drive current. Li-ion cells rated at a
4.2V charging voltage will be charged to approximately 90% of their rated capacity when charged to 4.1V by
the EnerChip CC. The 10% reduction in discharge capacity will be offset by an increase in the charge/discharge
cycle life. The charging voltage on VCHG is temperature compensated, thus ensuring longer service life of the
EnerChips and external Li-ion batteries by lowering the charging voltage at elevated temperatures.
See DS-72-03 EnerChip CC CBC3150 Datasheet or DS-72-04 EnerChip CC CBC3112 Datasheet for complete
specifications of the respective Enerchip CC.
©2010 Cymbet Corporation • Tel: +1-763-633-1780 •
AN-1041 Rev A
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