EnerChip Solar Energy Harvesting Demo Kit

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DS-72-08 Rev18

Page 3 of 11

Connecting CBC-EVAL-08 to the System

The CBC-EVAL-08 board has two control lines that can be connected to a microcontroller (MCU) for the purpose

of conserving available energy, using incoming power efficiently, and extending EnerChip life. The table below

describes the functionality of the J1 and J5 connector pins.

V

current. It provides power to the system according to the Operating Characteristics table shown below.

GND is the ground connection of the CBC-EVAL-08. It is to be connected to the system ground line.

•

V

power to a load.

BATOFF is typically controlled by a microcontroller I/O line. When driven high, the on-board EnerChips will

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be disconnected from the charging source of the CBC-EVAL-08. 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-08 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-08 that will be forced low under one of two conditions:

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When transducer output power is very low, a low level on CHARGE indicates that the

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EnerChips have been charged.

CHARGE will also be driven low when transducer output power is more than sufficient to operate

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the boost converter and charge the EnerChips at peak rate, regardless of the state of charge of the

EnerChips. Programming an MCU timer to allow enough charging time to elapse after the assertion

of CHARGE will ensure that the EnerChips are fully charged before using them to deliver power to the

system. The advantage is that the system is then aware of the minimum reservoir of energy available in

the event transducer power goes to zero.

J1 and J5 Pin Descriptions

Pin

Designation

BATOFF

Input control line to the CBC-EVAL-08 for disconnecting the

EnerChips from the CBC-EVAL-08 charging circuit. See the section

Circuit Recommendations to Save Power for additional information.

CHARGE

Active low output from the CBC-EVAL-08 indicating that the Ener-

Chips have been charged or are being charged. This is an open

drain output with an internal 10MΩ pull-up resistor to V

the section Circuit Recommendations to Save Power for additional

information.

V

BAT

(not accessible from the J1 connector)

Connected indirectly to the EnerChips’ positive terminals through

an isolation FET. Voltage is one diode drop above the potential at

V

OUT2.

V

OUT2

System power

GND

System ground