DS-72-40 Datasheet, PDF (5/17 Pages) Cymbet Corporation – EnerChip™ CC Energy Harvester Evaluation Kit

CBC-EVAL-10B EnerChip CC EH Evaluation Kit
• BATOFF is typically controlled by a microcontroller I/O line. When driven high, the CBC3150 charge pump
will be disabled. This feature allows all available power to be delivered to the load rather than to charging
the EnerChips, a useful mode when limited transducer power is available or when higher operating current
is required from the system. When BATOFF is driven low, the interaction between the charging source and
the CBC-EVAL-10B behaves normally. In other words, when BATOFF is low the EnerChips will always be
charging when sufficient input power is available.
• CHARGE/ is an output signal from the CBC-EVAL-10B. CHARGE/ is a filtered logical inversion of the
CBC3150 RESET/ output signal. Therefore, CHARGE/ will be driven low (RESET/ driven high) whenever VIN
is at a voltage above the VMODE switchover setpoint (nominally 3.0V with VMODE tied to GND). In CCEH
mode - as configured by jumper J11 - RESET/ is tied to EN, meaning the charge pump will be active and the
batteries will be charging only when RESET/ is high. During operating conditions when RESET/ is toggling
on and off at some duty cycle (for example in low light), CHARGE/ will not toggle but send a filtered version
that does not toggle. To determine whether the batteries are charged during such conditions, an MCU
could be programmed to interrogate the CHARGE/ to determine whether the batteries are charged and
available for use.
• VOUT is the DC output voltage from the CBC-EVAL-10B and is typically 3.2V depending on system
configuration and load current. It provides power to the system according to the Operating Characteristics
table shown below.
• GND is the ground connection of the CBC-EVAL-10B. It is to be connected to the system ground line.
CCEH Energy Harvesting
The energy harvesting technique used in the CBC-EVAL-10B is referred to as CCEH for Charge Controller Energy
Harvesting. This technique uses the ASIC inside the CBC-3150 part to harvest energy from a transducer such
as a solar cell at its Maximum Peak Power Point (MPPT). The most basic circuit implementing CCEH has a
capacitor on the input of the CBC-3150 to charge up from the solar cell to a voltage where the RESET/ line
on the CBC-3150 part transitions high meaning that the input voltage is higher than the VMODE comparator
threshold. Since RESET/ is wired to the charger EN pin, when RESET/ goes high it starts the charger which
moves charge from the input capacitor to the EnerChip at a higher voltage to charge the EnerChip. The
movement of charge out of the input capacitor draws the input voltage down since it is assumed that the solar
cell is relatively high in impedance and cannot supply enough current to power the charger. This action causes
the RESET/ line to drop which turns off the charger and allows the input capacitor to again charge up from the
input transducer. In this manner the input capacitor is held to nearly the VMODE threshold and the transducer
delivers its current into essentially a fixed voltage which must be selected to be the MPPT voltage of the
transducer for maximum efficiency.
The CBC-EVAL-10B uses the basic CCEH harvesting technique but also implements some optional circuitry to
improve its performance in startup and to add some useful features. The following sections describe the input
and output circuit additions.
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DS-72-40 Rev C

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