Cymbet CBC050-M8C Enerchipâ ¢ cc energy harvester evaluation kit Datasheet

CBC-EVAL-10
EnerChip™ CC Energy Harvester Evaluation Kit
System Features and Overview
CBC-EVAL-10 is a demonstration kit that provides
designers a platform to easily develop Energy
Harvesting (EH) solutions using the EnerChip
CBC3150TM configured to operate in an energy
harvesting mode. The kit combines a small solar
panel, power management circuit, energy storage,
regulated output voltage, and input/output pins for
connection to commercially available microcontroller
(MCU) and radio boards. A 16-pin CBC51100 module
is included, providing the EH functions, battery
management, and 100µAh solid state rechargeable
energy storage. CBC-EVAL-10 is a practical, low
cost realization of an EH-based power system that
can provide many years of service without need of
battery maintenance.
•
•
Controls charge voltage and discharge cutoff
circuit for maximizing the service life of the
EnerChip solid state batteries within the CBC3150
and auxiliary CBC050 energy storage device on
the CBC51100 module.
Manages internal circuitry for switching from PV
power to EnerChip (or external battery) power when
ambient light level is too low to power the system
and/or recharge the energy storage devices.
CBC-EVAL-10 is shown in Figure 1, including the 16pin CBC51100 EnerChip EH module and the PV cells
attached to the board via a 2-wire cable assembly.
CBC-EVAL-10 has the following elements:
•
•
•
•
•
The photovoltaic (PV) panel included in the CBCEVAL-10 converts ambient light energy into electrical
energy, which is fed into the CBC3150 device
residing on the CBC51100 module. The CBC3150
performs several important functions:
•
Decouples the load impedance from the PV cell
impedance to ensure maximum power conversion
efficiency from the PV transducer to the energy
storage and system load.
Figure 1: CBC-EVAL-10 Demo Kit.
A block diagram of CBC-EVAL-10 is shown in Figure 2.
Photovoltaic
Cells
Input Power Tracking
Battery Management
Power Management
Energy Storage
External Battery
and Control
(Optional)
CBC51100 Module
•
Energy harvesting circuitry that matches the
impedance of photovoltaic cells to ensure
maximum power transfer to system load and onboard energy storage devices
Solid state energy storage with thousands of
charge-discharge cycles available
Integrated battery management that controls
battery charging and discharge cutoff, ensuring
maximum service life of on-board storage cells
Provision for additional energy storage (primary
or rechargeable batteries) with switchover
control circuit to meet application requirements
Regulated output voltage with user-configurable
voltage settings
Input/output headers for connection to system
components such as radios and microcontrollers
Output Voltage
Regulation
I/O Control
Figure 2: EnerChip CBC-EVAL-10 Demo Kit block diagram.
The functions in the center block are performed by the
EnerChip CBC51100 module.
©2011 Cymbet Corporation • Tel: +1-763-633-1780 • www.cymbet.com
DS-72-20 Rev A
Page 1 of 15
CBC-EVAL-10 EnerChip CC EH Evaluation Kit
Operating Modes
CBC-EVAL-10 can be configured to operate in any of three modes, as required by the application. The operating
mode is set by configuring the various jumpers on the CBC-EVAL-10. [See Figure 3 and the associated tables for
jumper settings associated with each of the operating modes.] The three operating modes are as follows:
1. Standard energy harvesting mode using PV cells, on-board EnerChips, regulated output voltage, and
switchover control circuit to ensure a seamless transition from PV power to EnerChips when little or no
ambient light is available. In this mode, power from the PV cells is used to power the system load and
charge the EnerChips when sufficient light is available. With very low or no ambient light, the system
operates from on-board EnerChips. Variations of this mode are configured using jumper select pins J11,
allowing the user to drive the internal charge pump of the CBC3150 through one of three control methods,
as indicated on the silk screen next to J11:
a) EH: External control using the BATOFF control line. Used when an external microcontroller derives
input from CHARGE/ in an ‘energy-aware’ operating mode.
b) CCEH: CBC3150 RESET/ output is fed to CBC3150 ENABLE input in a standard transducer impedance matching mode.
c) CPEH: VIN controls the CBC3150 ENABLE line. When the input transducer voltage falls below 2.5V,
the CBC3150 charge pump is disabled.
2. Energy harvesting mode that relies on not only the on-board EnerChips for energy storage, but also taps
into the capacity of a conventional non-rechargeble battery when the EnerChips are at low state-of-charge,
such as during extended periods of darkness. Typical batteries might be 2-series alkaline cells, primary
coin cells, or certain cylindrical cells having output voltage of 3V to 3.6V. This ‘battery assist’ energy
harvesting mode can be used to supplement conventional batteries, extending their operational life by
months or years.
3. Energy harvesting mode that uses not only the PV cells and on-board EnerChips, but also an external
rechargeable battery such as a rechargeable coin cell or other small, Li-ion or Li-polymer cells having a
charging voltage of ~4.1V. This ‘extra capacity’ operating mode allows the designer to incorporate a higher
capacity rechargeable battery in order to achieve longer system run-time in periods of darkness than what
the EnerChips can provide, while avoiding the relative bulk associated with non-rechargeable cells.
In all operating modes, the input power source - whether PV cells, EnerChips, or external battery - passes
through a linear drop-out regulator (LDO) that supplies power to VOUT. The LDO output voltage is set at 2.5V
but can be modified to 3.0V - through selection of J12 and J13 solder traces - or to 2.2V or 3.3V by replacing
regulator U4 with regulator U6 (not populated) as indicated in the schematic of Figure 4 and Table 1: CBCEVAL-10 Bill of Materials. A power-on-reset (POR) circuit drives the LDO ENABLE pin in all operating modes
except when an external non-rechargeable battery is providing power to the LDO. To avoid starving the external
system elements of power particularly during start-up or when pulse currents are required by the system, the
POR circuit enables the LDO only after the output capacitors are fully charged to a voltage above the LDO
drop-out voltage. Consequently, the user must recognize the relationship between the POR trip voltage and the
LDO turn-on voltage when designing with a POR/LDO combination other than the components installed on the
CBC-EVAL-10 module.
©2011 Cymbet Corporation • Tel: +1-763-633-1780 • www.cymbet.com
DS-72-20 Rev A
Page 2 of 15
CBC-EVAL-10 EnerChip CC EH Evaluation Kit
External Control of the CBC-EVAL-10 Energy Harvesting Functions
In addition to protecting the EnerChips from being discharged too deeply in low ambient light conditions or
abnormally high current load conditions, the CBC3150 power management circuit also ensures that the
system load is powered with a smooth power-on transition. The power management circuit 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 external controller to disable the CBC3150 charge pump. Use of these
two control lines is optional.
There are several connectors on CBC-EVAL-10 for connection to target devices to be powered. Either the J9 or
J10 connector can be used for low power microcontroller-based systems. In the case of a low power wireless
end device, the CBC-EVAL-10 has storage energy for approximately 1000 radio transmissions - depending on
protocol used - in no/low ambient light conditions.
Microcontroller-based systems that are powered by the CBC-EVAL-10 should contain firmware that is “Energy
Harvesting Aware” and take advantage of the power management status and control signals available on CBCEVAL-10.
Using Additional EnerChips and External Batteries
The CBC-EVAL-10 is designed to permit attachment of rechargeable and non-rechargeable batteries whereby
the energy harvesting circuitry extends the life of those batteries by operating from (i) PV cell power when sufficient light is available, (ii) EnerChips when in an acceptable state-of-charge, and (iii) the external battery when
neither of those two conditions exists.
Two classes of external batteries may be attached to the CBC-EVAL-10:
1. A primary battery (i.e., non-rechargeable) or series combination of primary batteries may be connected to
header pins J3 only. The acceptable voltage range is 2.7 to 3.6. Commonly used batteries in this category
are: A single 3V CR-type or BR-type coin cell (e.g., CR2032, BR2032), or two alkaline cells (e.g., AAA, AA, C,
D) connected in series. A single 3.6V thionyl chloride cell may also be used. Contact Cymbet for recommendations in selecting a primary battery for your application.
2. A secondary (i.e., rechargeable) battery may be connected to header pins J7 only. The acceptable charging
voltage range is 4.0V to 4.2V. The charging source for this battery is the VCHG output pin of the CBC3150
that normally charges the EnerChips to 4.1V. Maximum drive current of this pin is on the order of 1mA.
VCHG drive current can be adjusted by populating capacitor C9 (module shipped without a capacitor).
See DS-72-03 EnerChip CC CBC3150 Data Sheet for guidelines on sizing the charge pump capacitor. The
discharge cutoff voltage is fixed at 3.0V +/- 0.3V. Examples of rechargeable batteries supported by CBCEVAL-10 are the LiR-type coin cells, including LiR-1220 (~8mAh) and LiR-2032 (~40mAh). The charging
rate for these external cells will be a function of available light, to a maximum of 1mA as limited by the
CBC3150 charge pump drive current.
To operate the CBC-EVAL-10 board for use with an external battery, configure the header pins as follows:
1. Non-rechargeable (i.e., primary) battery connected to EXT BAT terminal block J3:
J1 and J2 - shorted
J4, J5, J6 - not shorted
J7 - no connection
2. Rechargeable (i.e., secondary) battery connected to header pins J7:
J1, J2 - not shorted
J3 - no connection
J4, J5, and J6 - shorted
©2011 Cymbet Corporation • Tel: +1-763-633-1780 • www.cymbet.com
DS-72-20 Rev A
Page 3 of 15
CBC-EVAL-10 EnerChip CC EH Evaluation Kit
CBC-EVAL-10 Module Connectors, Jumpers, and Test Points
CONNECTORS
J2
Connector
J14
J6
J5
J4
J3
J1
TP2
TP1
Designation
1
External Primary
Battery Input (+)
2
External Primary
Battery Input (-)
J3
J7
TP3
J8
Connector Type: Terminal Block
CBC51100
TP4
1
J10
J9
J11
1
External
Rechargeable
Battery Input (+)
2
External
Rechargeable
Battery Input (-)
J7
1
Connector Type: vias
J15
J8
TP5
J9
Figure 3: Locations of connectors, jumpers, and test points.
JUMPERS
PV Cell Input (+)
2
PV Cell Input (-)
1
CHARGE/
2
BATOFF
3
No Connection
4
GND
5
VOUT
Connector Type: Vertical SIP
Jumper
Pin
Number
Designation
J1
1-2
External Battery to LDO Enable
J2
1-2
External Battery Mode Enable
J4
1-2
External Battery Bypass
J5
1-2
VOUT to LDO Enable
J6
1-2
Voltage Threshold Detect to LDO Enable
1-2
External Control of Energy Harvesting
3-4
Normal Energy Harvesting Mode
5-6
Disable Energy Harvesting
PCB TRACES and PADS
1
Connector Type: Terminal Block
J12 J13
J11
Pin
Number
J10
1
BATOFF
2
GND
3
No Connection
4
No Connection
5
VOUT
6
CHARGE/
Connector Type: Right Angle SIP
TEST POINTS
Test Point
Designation
TP1
External Primary Battery (+)
Reference
Designation
TP2
GND
J12
LDO Voltage Select
TP3
DC Input (PV+)
J13
LDO Voltage Select
TP4
VOUT
J15
Schottky Diode Bypass
TP5
GND
©2011 Cymbet Corporation • Tel: +1-763-633-1780 • www.cymbet.com
DS-72-20 Rev A
Page 4 of 15
CBC-EVAL-10 EnerChip CC EH Evaluation Kit
CBC-EVAL-10 Module Connector Descriptions
J3: Terminal block for connecting the positive and negative terminals of an external non-rechargeable battery.
See specifications elsewhere in this document for the minimum and maximum allowable battery voltage before
attaching a battery to this connector.
J7: Header pins to be used only for the purpose of connecting the positive and negative terminals of an
external 4.1V rechargeable battery. No other connections are allowed on these pins and the pins are not to
be shorted together. See specifications elsewhere in this document for the minimum and maximum allowable
external battery voltage before attaching a battery to this connector.
J8: Terminal block for connecting a photovoltaic cell (or other DC voltage). See specifications elsewhere in this
document for the minimum and maximum allowable DC voltage to be applied to this connector.
J9 and J10: Power and handshaking signals for connection to a target board - e.g. wireless end-point module.
(For reference, header connector J9 is a 5-pin section of Samtec 50-pin header p/n TSW-150-07-G-S. Header
connector J10 is Mill-Max p/n 850-10-006-20-001000; the socket it mates to is Mill-Max p/n 851-93-006-20001000.)
J14: Used for factory test purposes only. Do not make any connections to J14.
Cable Assembly - A 5-conductor cable with a header connector at each end is provided with CBC-EVAL-10 to
facilitate connection between the J9 connector and a 5-pin header on the user’s board.
Getting Started
To operate the CBC-EVAL-10 in the standard energy harvesting mode, using the EnerChips as the storage
devices, leave each of the several jumpers in the same position as received. The factory default settings are as
follows:
Header
J1
J2
J3
J4
J5
J6
J7
J8
J9
J10
J11
J12
J13
J14
J15
Shorting Jumper, Connector, or Solder Trace/Pad
No
No
No
Yes
Yes
Yes
No. DO NOT APPLY A SHORTING JUMPER TO J7 UNDER ANY CIRCUMSTANCES! Doing so will destroy the EnerChips.
PV Cell Input (2.5VDC to 5.5VDC)
System I/O (See J9 and J10 Pin Descriptions Table)
System I/O (See J9 and J10 Pin Descriptions Table)
Pin 3 to Pin 4
Leave as is for 2.5V Regulated Output (Cut J12 and Short J13 for 3.0V Regulation)
Leave as is for 2.5V Regulated Output (Cut J12 and Short J13 for 3.0V Regulation)
No Connections Necessary (Used for Factory Testing)
Leave as is for 2.5V Regulated Output
©2011 Cymbet Corporation • Tel: +1-763-633-1780 • www.cymbet.com
DS-72-20 Rev A
Page 5 of 15
CBC-EVAL-10 EnerChip CC EH Evaluation Kit
After confirming the header pins are properly configured, simply connect the 2-wire cable assembly from the PV
panel to jumper J8. [Note polarity; red wire goes to the positive terminal, pin 1.]
Expose the PV panel to ambient light of greater than 200 Lux. The EnerChip storage devices on the CBC51100
module will begin to charge and power will be supplied to the load via header pins J9 and J10. The magnitude
of power available to the load will be a function of the ambient light, the angle of incidence of light to the PV
panel, and the state of charge of the EnerChips.
To verify that the circuit is operating properly, measure the voltage on any of the readily accessible test points:
Test Point
TP1
TP2
TP3
TP4
TP5
Node Description
External Battery Terminals
System Ground
PV Input
Regulated Output
System Ground
The various header pins may also be used as test measurement points. Refer to the schematic of Figure 4.
Reference the CBC3150 data sheet for operating characteristics of the CBC3150.
Users may populate R2 and R3 to set the maximum power point of the DC transducer. See the CBC3150 data
sheet for recommended resistor values. Note that the resistor divider will present a parasitic load to the transducer.
©2011 Cymbet Corporation • Tel: +1-763-633-1780 • www.cymbet.com
DS-72-20 Rev A
Page 6 of 15
CBC-EVAL-10 EnerChip CC EH Evaluation Kit
Connecting CBC-EVAL-10 to the System
The CBC-EVAL-10 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 battery life. The table
below describes the functionality of the J9 and J10 connector pins.
J9 and J10 Pin Descriptions
Pin
Designation
BATOFF
Input control line to the CBC-EVAL-10 for disconnecting the EnerChips
from the CBC-EVAL-10 charging circuit. See the section System Design
Recommendations to Save Power for additional information.
CHARGE/
Active low output from the CBC-EVAL-10 indicating that the EnerChips
have been charged or are being charged (provided CBC3150 EN pin was/
is high). CHARGE/ is an open drain output with an internal 1.0MΩ pull-up
resistor to VOUT. See the section System Design Recommendations to
Save Power for additional information.
VOUT
CBC-EVAL-10 output power
GND
System ground
NC
No connection
(J9 has one NC pin and J10 has two NC pins)
• 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-10 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-10. CHARGE/ is a 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 also be toggling. To determine whether the
batteries are charged during such conditions, an MCU could be programmed to integrate the total time
that CHARGE/ is low over some elapsed time or pre-defined use period. From that data, it can be inferred
whether the batteries are charged and available for use in the event input power (VIN) drops below the level
required to operate the charge pump at all.
• VOUT is the DC output voltage from the CBC-EVAL-10 and is typically 2.5V, 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-10. It is to be connected to the system ground line.
©2011 Cymbet Corporation • Tel: +1-763-633-1780 • www.cymbet.com
DS-72-20 Rev A
Page 7 of 15
CBC-EVAL-10 EnerChip CC EH Evaluation Kit
Operating Characteristics (1)
Parameter
Input Luminous Intensity (using PV cells
provided with kit)
Typical
Max
Units
-
-
Lux
Lux
Volts DC
3.0
3.6
Volts DC
Rechargeable
4.0
4.1
4.2
Volts DC
1000 Lux (FL); battery
not charging; continuous
output
-
300
-
µA
200 Lux (FL), battery not
charging
-
10
-
µA
No ambient light, EnerChips charged
-
2000 (4)
-
µA
Battery charged; 2µA
load
2.48
2.5
2.52
V
4.7kΩ load
3.0
3.3
3.6
V
25°C ; 20 msec pulse
-
30 (5)
-
mA
5-year average
25°C
-
2.5
-
% per year
Pulse Discharge Current
EnerChip Self-Discharge (non-recoverable)
Operating Temperature
-
0
25
70
°C
10% depth-of-discharge
5000
-
-
-
50% depth-of discharge
1000
-
-
-
10% depth-of-discharge
2500
-
-
-
50% depth-of-discharge
500
-
-
-
-
10
-
minutes
-
50
-
minutes
100
-
-
µAh
From 50% state-of-charge
EnerChip Recharge Time (to 80% of rated
capacity)
From deep discharge
EnerChip Storage Capacity
5.5
2.7
EnerChip and External Rechargeable Battery Discharge Cutoff Voltage
40°C
3.2 (3)
Non-rechargeable
VOUT
25°C
800
(2)
25°C
External Battery Voltage
EnerChip Recharge
Cycles
(to 80% of rated
capacity; 4.1 V charge
voltage)
Min
250 (2)
Full charge rate
Photovoltaic Input Voltage (VIN)
Continuous Output Power
(measured at VOUT pin; 25°C)
Condition
Minimum operating Lux
200 µA discharge; 25°C
(1) See DS-72-03 EnerChip CC CBC3150 Data Sheet and DS-72-01 EnerChip CBC050 Data Sheet for complete specifications of the Cymbet components on the CBC51100 module included with CBC-EVAL-10.
(2) Fluorescent (FL) light conditions. EnerChip state-of-charge >90%.
(3) Dependent on battery state-of-charge and load conditions. State-of-charge will affect average VIN. At 0% battery stateof-charge, 2.6V < VIN < 3.1V, depending on load. At 100% battery state-of-charge, VIN will approach 5.2V at 700Lux.
(4) Continuous current for up to 1 minute with CBC51100 EnerChip module.
(5) For guidelines on adjusting the pulse current capability, see AN-1025: Using the EnerChip in Pulse Current Applications.
Specifications subject to change without notice.
CBC-EVAL-10 Circuit Schematics
As a result of designing the CBC-EVAL-10 to be versatile and useful for designing to any number of operating
environments and system requirements, there are many circuit elements that will not be necessary for any
given CCEH implementation. The full schematic of Figure 4 depicts the CBC-EVAL-10 in its entirety. A simpler
and more often used embodiment is shown in Figure 5. In Figure 5, the provision for external batteries has
been removed, as has the circuitry required for external system control of the CBC3150 charge pump. The
schematic of Figure 5 is reduced to the essential elements necessary for implementing an energy harvestingbased design using the CBC3150 circuitry and EnerChip batteries.
©2011 Cymbet Corporation • Tel: +1-763-633-1780 • www.cymbet.com
DS-72-20 Rev A
Page 8 of 15
CBC-EVAL-10 EnerChip CC EH Evaluation Kit
CBC-EVAL-10 Circuit Schematic
Figure 4: CBC-EVAL-10 Circuit Schematic.
©2011 Cymbet Corporation • Tel: +1-763-633-1780 • www.cymbet.com
DS-72-20 Rev A
Page 9 of 15
Figure 5: CBC-EVAL-10 Circuit Schematic with External Battery and External System Control Circuits Removed.
©2011 Cymbet Corporation • Tel: +1-763-633-1780 • www.cymbet.com
DS-72-20 Rev A
Page 10 of 15
CBC-EVAL-10 EnerChip CC EH Evaluation Kit
CBC-EVAL-10 Assembly Diagram
Figure 6: CBC-EVAL-10 Assembly Diagram (Top View).
Table 1: CBC-EVAL-10 Bill of Materials.
©2011 Cymbet Corporation • Tel: +1-763-633-1780 • www.cymbet.com
DS-72-20 Rev A
Page 11 of 15
CBC-EVAL-10 EnerChip CC EH Evaluation Kit
Using Other Energy Harvesting Transducers
CBC-EVAL-10 includes a standard amorphous silicon solar panel (Sanyo AM1815 type) configured as 8 seriesconnected cells on a glass substrate. The output voltage and current vary with incident light intensity, wavelength, and load impedance.
DC sources other than the PV cell provided with the CBC-EVAL-10 may also be used as the energy harvesting
power transducer. While the CBC-EVAL-10 module has a Zener diode at the transducer input to limit high voltage excursions at 5.6V, it is recommended that any DC transducer input be limited to 5.5V under all anticipated operating conditions. The minimum input voltage required to activate the internal charge pump of the
CBC3150 is 2.5V. At <2.5V, the EnerChips will not charge and the power management circuit will not function.
It is recommended that the input power source have a maximum power operating point above 3.0V. Operating
characteristics for most transducers are typically available from the manufacturer’s data sheet. An example
photovoltaic cell operating curve is shown below. Output impedance, operating voltage, and peak power point
can also be verified by empirical measurements. To determine the peak power point of a given PV cell, measure
the load voltage and current as a variable load impedance across the transducer is swept over a broad enough
range where the peak power point can be found by finding the maximum product of the measured load voltage
and current.
VOC: Open-circuit voltage
ISC: Short-circuit current
VOP: Optimum operating voltage
IOP: Optimum operating current
PMAX: Maximum operating power
Current-Voltage Curve
Once the peak power point of the PV cell has been determined, the CBC3150 operating point can be adjusted
to match the PV cell. This is done by adding a resistor divider R2 and R3 to the CBC-EVAL-10 module. As
shipped, those resistors are not populated. Cut the solder trace in the R2 location prior to adding the resistor.
Resistor values should be sized according the guidelines in the CBC3150 data sheet. It is important to note
that the resistor divider will present a permanent parasitic load to the PV cells and therefore the calculation
should be made to determine whether the standard CBC3150 impedance matching setpoint of ~3V - though it
might not be at the peak power point of a particular PV cell - is preferred to the more optimized setpoint when
considering the additional parasitic load on the PV resulting from the added resistor divider.
©2011 Cymbet Corporation • Tel: +1-763-633-1780 • www.cymbet.com
DS-72-20 Rev A
Page 12 of 15
CBC-EVAL-10 EnerChip CC EH Evaluation Kit
System Design Recommendations to Save Power
In most system power budgets, the peak power required is not as critical as the length of time the power is
required.
1. Careful selection of the message protocol for the RF link can have a significant impact on the overall power
budget.
2. In many cases, using higher power analog circuits that can be turned on, settle quickly, and immediately
turned off can decrease the overall energy consumed.
3. Microcontroller clock frequency can also have a significant impact on the power budget.
4. In some applications it might be advantageous to use a higher microcontroller clock frequency to reduce
the time the microcontroller and peripheral circuits are active.
5. Avoid using circuits that bias microcontroller digital inputs to mid-level voltages; this can cause significant
amounts of parasitic currents to flow.
6. Use 22MΩ (or larger) pull-up/down resistors where possible. However, be aware that high circuit
impedances coupled with parasitic capacitance can make for a slow rise/fall time that can place the
voltage on the microcontroller inputs at mid-levels, resulting in parasitic current flow. One solution to
the problem is to enable the internal pull-up/down resistor of the microcontroller input to force the input
to a known state, then disable the resistor when it’s time to check the state of the line. If using the
microcontroller’s internal pull-up/down resistors on the inputs to bias push-button switches in a polled
system, leave the pull-up/down resistor disabled and enable the resistor only while checking the state of
the input port. Alternatively, in an interrupt-driven system, disable the pull-up/down resistor within the first
few instructions in the interrupt service routine. Enable the pull-up/down resistor only after checking that
the switch has been opened.
7. Microcontroller pull-up/down resistors are typically less than 100kΩ and will be a huge load on the system
if left on continuously while a button is being pressed or if held for any significant length of time. For
even greater reduction in power, use external pull-up/down resistors in the 10MΩ to 22MΩ range. Bias
the external resistor not with the power rail but with a microcontroller port. The same algorithm used for
internal pull-up/down resistors can then be used to save power.
8. The CHARGE/ line on the CBC-EVAL-10 has a 1.0MΩ pull-up resistor with a very slow rise time. Use an
internal microcontroller pull-down resistor to force the CHARGE/ line low all of the time and then disable
the pull-down resistor to check the state of the line. This will keep the CHARGE/ line from biasing the input
at mid level for long periods of time, which could case large parasitic currents to flow.
9. The CBC-EVAL-10 module has a feature for disabling the CBC3150 charge pump. A handshake line BATOFF
is provided for use of this feature. A high level will disable the charge pump. This is useful in very low
ambient energy conditions to steer all of the available energy into the load. EnerChip batteries have very
low self-discharge rates (typically 2.5% per year) so it is not necessary to continuously charge them.
10. While it is relatively straightforward to calculate a power budget and design a system to work within the
constraints of the power and energy available, it is easy to overlook the power required to initialize the
system to a known state and to complete the radio link with the host system or peer nodes in a mesh
network. The initialization phase can sometimes take two to three times the power needed for steady state
operation. Ideally, the hardware should be in a low power state when the system power-on reset is in its
active state. If this is not possible, the microcontroller should place the hardware in a low power state as
soon as possible. After this is done, the microcontroller should be put into a sleep state long enough for
the energy harvester to replenish the energy storage device. If the power budget is not exceeded during
this phase, the system can continue with its initialization. Next, the main initialization of the system, radio
links, analog circuits, and so forth, can begin. Care should be taken to ensure that the time the system
is on during this phase does not exceed the power budget. Several sleep cycles might be needed to
‘stairstep’ the system up to its main operational state. The Cymbet CBC-EVAL-10 module has a handshake
line CHARGE/ to indicate to the microcontroller when energy is available. Another way to know whether
energy is available is to have the microcontroller monitor the voltage on its power bus using one its internal
A/D converters.
©2011 Cymbet Corporation • Tel: +1-763-633-1780 • www.cymbet.com
DS-72-20 Rev A
Page 13 of 15
CBC-EVAL-10 EnerChip CC EH Evaluation Kit
Frequently Asked Questions
Q:
A:
I am not sure if I have enough input power to charge the EnerChip batteries?
Measure the voltage on pin 1 of header connector J7. If the voltage is 4.1V, the EnerChips (and external rechargeable battery connected to J7, if any) are being charged. If the voltage is not 4.1V (+/- 50mV), there is insufficient power to charge the batteries.
Q:
A:
What if I short-circuit the output?
The disconnect circuit will disconnect the EnerChip devices from the output after the capacitor is discharged below about 3.0V. This prevents the EnerChips from being discharged too deeply. The EnerChip cell will automatically reconnect after the capacitor is recharged.
Q:
A:
What happens if I want to run a larger pulse current application?
See application note AN-1025. The output capacitor can be sized to drive almost any load as long as the duration is not too long. AN-1025 describes how to calculate the capacitor size.
Q:
A:
What happens if the EnerChip is short-circuited? Will it explode or leak harmful chemicals?
No. There are no harmful chemicals to leak and the energy storage cells will not explode.
Q:
A:
How long will the CBC-EVAL-10 module operate with no ambient light?
This depends on many factors, including load power consumption, EnerChip state-of-charge, operating temperature, etc. The EnerChips on the CBC51100 module provide 100µAh of discharge capacity when fully charged.
Q:
How long will the CBC-EVAL-10 module last if I use it every day and input power is available most of the
time?
The CBC-EVAL-10 module should last at least 10 years.
A:
Q:
A:
How long will the two EnerChips on the CBC51100 module hold a charge, assuming no input power?
The self-discharge of the EnerChip is a function of several parameters, including temperature. Self-
discharge specifications can be found in the product data sheets at http://www.cymbet.com/content/
products-resource-docs.asp.
Q:
A:
What happens if the EnerChip is left in a discharged state for a long period of time?
Leaving the EnerChip in a discharged state is not detrimental to its performance.
Q:
A:
I see no voltage on VOUT.
Make sure there is sufficient input power to operate the CBC3150 charge pump and that the output is not short-circuited.
Q:
A:
Will the CBC-EVAL-10 disconnect the EnerChips before they become too deeply depleted?
Yes, the CBC-EVAL-10 has a cutoff circuit that will prevent the EnerChips from being damaged due to over-discharge. However, repeatedly operating the system in a mode that allows the cutoff
circuit to be invoked at deep discharge will cause premature capacity fade and shorter product life. If it is anticipated that the low voltage cutoff point will be reached, it is better to put the system into a high power mode to force cutoff at a higher state-of-charge, thereby prolonging the life of the EnerChips.
©2011 Cymbet Corporation • Tel: +1-763-633-1780 • www.cymbet.com
DS-72-20 Rev A
Page 14 of 15
CBC-EVAL-10 EnerChip CC EH Evaluation Kit
Power Conversion Efficiency Considerations
System factors such as PV cell properties; ambient light; input and output capacitor sizes; battery state-ofcharge; and CBC3150 VMODE peak power setting will all affect the duty cycle of the CBC3150 charge pump
and system power conversion efficiency.
The CBC3150 has a built-in latency of about 200ms with respect to the timing of RESET/ being asserted low after the charge pump is disabled. For optimum power conversion efficiency, size the input capacitor so that it will
only charge one or two tenths of a volt during that 200ms period under the lowest anticipated lighting condition
- that is, where the PV cell gives its lowest power output.
For example, suppose the PV cell at 200Lux can deliver 50µA at a maximum power point of 3.0V. Transposing
the standard equation I = C x dv/dt, the input capacitor can be sized as C = 50µA x 200ms/100mV = 100µF of
capacitance. When the charge pump runs, it will quickly pump the capacitor to the switching point. When the
charge pump stops during the 200ms latency time, the capacitor will not charge above the maximum power
point. At higher light intensity, the efficiency is less important and thus the capacitor does not need to be oversized to maintain operation at the peak power point of the PV cell.
Ordering Information
EnerChip Part Number
Description
Notes
CBC-EVAL-10
EnerChip CC Energy Harvester
Evaluation Kit
Contains Solar Cell Panel and
CBC51100 Module
CBC3150-D9C
EnerChip CC with Integrated Power
Management
Packaged in Tape and Reel or
Tubes
CBC050-M8C
EnerChip 50µAh Solid State
Battery
Packaged in Tape and Reel or
Tubes
Disclaimer of Warranties; As Is
The information provided in this data sheet is provided “As Is” and Cymbet Corporation disclaims all representations or warranties of any
kind, express or implied, relating to this data sheet and the Cymbet battery product described herein, including without limitation, the
implied warranties of merchantability, fitness for a particular purpose, non-infringement, title, or any warranties arising out of course of
dealing, course of performance, or usage of trade. Cymbet battery products are not approved for use in life critical applications. Users shall
confirm suitability of the Cymbet battery product in any products or applications in which the Cymbet battery product is adopted for use and
are solely responsible for all legal, regulatory, and safety-related requirements concerning their products and applications and any use of
the Cymbet battery product described herein in any such product or applications.
Cymbet, the Cymbet Logo and EnerChip are trademarks of Cymbet Corporation. All Rights Reserved.
EnerChip products and technology are covered by one or more patents or patents pending.
©2011 Cymbet Corporation • Tel: +1-763-633-1780 • www.cymbet.com
DS-72-20 Rev A
Page 15 of 15
Similar pages