CBC-EVAL-10B EnerChip CC EH Evaluation Kit

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DS-72-40 Rev C

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• 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.