Product Discontinued - Not for New Designs
CBC-EVAL-08
EnerChip™ EH Solar Energy Harvester Evaluation Kit
Features
CBC-EVAL-08 is a demonstration kit combining a
solar panel energy transducer with the CBC5300
EnerChip EH module having two rechargeable
50µAh EnerChip solid state energy storage devices
connected in parallel. The EnerChips provide
storage and starting power for the energy harvesting
module. The purpose of this demonstration platform
is to enable designers to quickly develop Energy
Harvesting applications. A block diagram of CBC-
EVAL-08 is shown in Figure 1.
Control
Lines
V
OUT
Photovoltaic
Cell
Boost
Converter
Connector
Power
Management
Figure 2: CBC-EVAL-08 Demo Kit - 3.55 x 2 (inches)
Charge
Control
2 - EnerChip
CBC050
the EnerChips from discharging too deeply in low
ambient light conditions or abnormally high current
load conditions. The power management block
also ensures that the load is powered up with a
smooth power-on transition. The power management
block has a control line (CHARGE) for indication to
the system controller that the energy harvester is
charging the EnerChips. A control line input (BATOFF)
is available for the controller to disconnect itself
from the EnerChips when it is necessary to extend
run time in prolonged low ambient light conditions.
CBC-EVAL-08 is shown in Figure 2 with the CBC5300
EnerChip EH module mounted on the solar board.
There are two connectors on CBC-EVAL-08 for
connection to target devices to be powered. Either
connector can be used for low power microcontroller-
based systems. In the case of a low power wireless
end device, the CBC-EVAL-08 has storage energy for
up to 1000 transmissions - depending on protocol
used - in no/low ambient light conditions.
Microcontroller-based systems that are powered by
the CBC-EVAL-08 should contain firmware that is
“Energy Harvesting Aware” and take advantage of
the power management status and control signals
available on CBC-EVAL-08.
Figure 1: EnerChip CBC-EVAL-08 Demo Kit Block Diagram,
with the Functional Elements of the CBC5300 EnerChip EH
Module Shown in the Shaded Region
System Description
Photovoltaic cells on CBC-EVAL-08 convert ambient
light energy into electrical energy. Because the
output voltage of the photovoltaic cells is too low
to charge the EnerChips and power the rest of the
system directly, a boost converter is used to raise
the photovoltaic cell voltage to the voltage needed to
charge the EnerChips.
The charge control block continuously monitors
the output of the boost converter. If the output of
the boost converter falls below the voltage needed
to charge the EnerChips, the charge controller will
disconnect the boost converter from the EnerChips.
This prevents the EnerChips from back-powering the
boost converter in low ambient light conditions.
The power management block is used to protect
DS-72-08 Rev A
©2009-2014 Cymbet Corporation • Tel: +1-763-633-1780 • www.cymbet.com
Page 1 of 11
EnerChip Solar Energy Harvesting Demo Kit
CBC-EVAL-08 Module Connectors
PT1
J7 J8
Solar Panel
EnerChip
EH
5300
Module
1
J5
1
J1
The CBC-EVAL-08 and CBC5300 modules are
sensitive to electrostatic discharge (ESD) and
must be handled accordingly. In cases where the
CBC-EVAL-08 or CBC5300 modules are removed
from their original packaging, it is a requirement
to maintain the same type of anti-static, non-
conductive packaging to prevent discharge of the
on-board EnerChips. Do not store the CBC-EVAL-08
or CBC5300 modules in conductive black foam, as
it will discharge and destroy the EnerChips on the
CBC5300 module.
J1 Connector for User
Pin Number(s)
1
2
3
4
5
6
Designation
J5 Connector for User
Pin Number(s)
1
2
3
4
5
Designation
CHARGE
BATOFF
1
J7 Connector
Pin Number(s)
Description
Cut Trace to use
external source
BATOFF
GND
Not
Connected
Not
Connected
V
BAT
GND
Connector Type: Circular pad and
trace
J8 Connector
Pin Number(s)
1
2
Designation
Positive input
GND
V
OUT2
V
OUT2
CHARGE
Connector Type: Vertical SIP
PT1 Connector
Pin Number(s)
1
2
Designation
Piezo input 1
Piezo input 2
Connector Type: Rt. Angle SIP
Connector Type: Trace Vias
Connector Type: Trace Vias
Figure 3: EnerChip EVAL-08 Connections
EVAL-08 Module Connector Explanations
J1 Connector
- Power and handshaking signals for connection to a target board - e.g. wireless end-point
module. (For reference, header connector J1 is Mill-Max p/n 850-10-006-20-001000; the socket it mates to is
Mill-Max p/n 851-93-006-20-001000.)
module. (For reference, header connector J5 is a 5-pin section of Samtec 50-pin header p/n TSW-150-07-G-S.
J5 Connector
- Power and handshaking signal pins for connection to a target board - e.g. wireless end-point
J7 Connector
- This trace is to be cut if an alternate solar panel is to be connected to J8.
is removed before CBC-EVAL-08 is charged for the first time. This connector can also be used to connect an
alternate solar panel to CBC-EVAL-08.
J8 Jumper and Shunt
- This connector ships with the shunt installed to protect the EH module. The shunt
PT1 Connector
- An alternate piezoelectric (or other AC) energy harvesting transducer can be connected.
It can be connected in parallel with the CBC-EVAL-08 solar panel by leaving J7 intact. Or, the piezoelectric
transducer can be used stand-alone by cutting the J7 trace.
Cable Assembly
- A 5-conductor cable with a header connector at each end is provided with CBC-EVAL-08 to
facilitate connection between the J5 connector and a 5-pin header on the user’s board.
DS-72-08 Rev A
©2009-2014 Cymbet Corporation • Tel: +1-763-633-1780 • www.cymbet.com
Page 2 of
EnerChip Solar Energy Harvesting Demo Kit
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.
Pin
BATOFF
J1 and J5 Pin Descriptions
Designation
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.
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
OUT2
. See
the section Circuit Recommendations to Save Power for additional
information.
Connected indirectly to the EnerChips’ positive terminals through
an isolation FET. Voltage is one diode drop above the potential at
V
OUT2.
System power
System ground
CHARGE
(not accessible from the J1 connector)
V
BAT
V
OUT2
GND
• V
OUT2
is the DC output voltage from the CBC-EVAL-08 and is approximately 3.5V depending on 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-08. It is to be connected to the system ground line.
• V
BAT
is normally used for factory test purposes. It is indirectly connected to the on-board EnerChips
through an isolation pass transistor. The voltage on V
BAT
is connected to V
OUT2
by a diode and thus the
voltage at V
OUT2
is one diode drop lower than the voltage on V
BAT
. It is recommended that V
BAT
remain
disconnected from external circuits. In no event should V
BAT
be used for any purpose other than to provide
power to a load.
• BATOFF is typically controlled by a microcontroller I/O line. When driven high, the on-board EnerChips will
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:
»
When transducer output power is very low, a low level on CHARGE indicates that the
EnerChips have been charged.
»
CHARGE will also be driven low when transducer output power is more than sufficient to operate
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.
DS-72-08 Rev A
©2009-2014 Cymbet Corporation • Tel: +1-763-633-1780 • www.cymbet.com
Page 3 of
EnerChip Solar Energy Harvesting Demo Kit
Operating Characteristics
Parameter
Input Luminous Intensity
Parasitic Load Current
Average Output Power
(measured at
V
OUT2
pin)
Condition
Minimum operating Lux
Full charge rate
Boost converter off
Boost converter on
1000 Lux (FL), EnerChips
not charging
200 Lux (FL), EnerChips
not charging
EnerChips charged
25°C
4.7kΩ load
20 msec
25°C
10% depth-of-discharge
50% depth-of discharge
40°C
10% depth-of-discharge
50% depth-of-discharge
From deep discharge
25°C
Min
200
(1)
700
(1)
-
-
-
-
3.5
-
3.0
-
-
5000
1000
2500
500
-
-
-
Typical
-
-
800
20
350
80
3.55
4.06
3.3
30
2.5
-
-
-
-
10
50
100
Max
-
-
-
-
-
-
3.6
-
3.6
-
-
-
-
-
-
-
-
-
Units
Lux
Lux
nA
µA
µW
µW
V
V
V
mA
% per year
-
-
-
-
minutes
minutes
µAh
V
OUT2
, 2 µA Load
V
BAT
Charging Voltage
EnerChip Cutoff Voltage
Pulse Discharge Current
Self-Discharge (non-recoverable average)
Recharge Cycles
(to 80% of rated
capacity; 4.1 V charge
voltage)
Recharge Time (to 80% of rated capacity) From 50% state-of-charge
Capacity
(1) Fluorescent (FL) Light Conditions
Specifications subject to change without notice
16 µA discharge; 25°C
EVAL-08 Circuit Schematic
Figure 4: EnerChip EVAL-08 Circuit Schematics
DS-72-08 Rev A
©2009-2014 Cymbet Corporation • Tel: +1-763-633-1780 • www.cymbet.com
Page 4 of
EnerChip Solar Energy Harvesting Demo Kit
Designing for Pulse Discharge Currents in Wireless Devices
Pulse currents of tens of milliamperes are common in wireless sensor systems during transmit and receive
modes. Pulse discharge currents place special demands on energy storage devices. Repeated delivery of
pulse currents exceeding the recommended load current of a given chemistry will diminish the useful life of
the cell. The effects can be severe, depending on the amplitude of the current and the particular cell chemistry
and construction. Moreover, the internal impedance of the cell often results in an internal voltage drop that
precludes the cell from delivering the pulse current at the voltage necessary to operate the external circuit.
One method of mitigating such effects is to place a low Equivalent Series Resistance (ESR) capacitor across
the main energy storage device. The storage device charges the capacitor between discharge pulses and the
capacitor delivers the pulse current to the load. Specifying the capacitance for a given energy storage device in
an application is a straightforward procedure, once a few key parameters are known. The key parameters are:
»
»
»
»
»
»
Storage cell impedance (at temperature and state-of-charge)
Storage cell voltage (as a function of state-of-charge)
Operating temperature
Pulse current amplitude
Pulse current duration
Allowable voltage droop during pulse discharge
Two equations will be used to calculate two unknown parameters:
1) the output capacitance needed to deliver the specified pulse current of a known duration;
2) the latency time that must be imposed between pulses to allow the capacitor to be recharged by the
main energy storage device such as the EnerChip solid state storage cell.
Both formulae will assume that the capacitor ESR is sufficiently low to result in negligible internal voltage
drop while delivering the specified pulse current; consequently, only the EnerChip device resistance will be
considered in the formula used to compute capacitor charging time and only the load resistance will be
considered when computing the capacitance needed to deliver the discharge current. The first step in creating
an EnerChip-capacitor couple for pulse current applications is to size the capacitance using the following
formula:
Discharge formula: C = t / [ R * ln (Vmax / Vmin) ]
where:
C = output capacitance, in parallel with EnerChip;
t = pulse duration;
R = load resistance = Vout(average) / Ipulse
Vmin and Vmax are determined by the combination of the EnerChip voltage at a given state-of-charge and the
operating voltage requirement of the external circuit.
Once the capacitance has been determined, the capacitor charging time can be calculated using the following
formula:
Charge formula: t = - R * C * ln [ (Vmax - Vchg) / (Vmin - Vchg) ]
where:
t = capacitor charging time, from Vmin to Vmax
R = EnerChip resistance
C = output capacitance, in parallel with EnerChip
Vmax = final voltage to which the capacitor must be charged prior to delivering the next current pulse
Vmin = initial voltage on the capacitor when charging begins
Vchg = applied charging voltage on the capacitor
DS-72-08 Rev A
©2009-2014 Cymbet Corporation • Tel: +1-763-633-1780 • www.cymbet.com
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