EA-APP-002 Embedded Artists, EA-APP-002 Datasheet - Page 14

• Manufacturer Part Number: EA-APP-002
• Description: Development Boards & Kits - ARM LOW POWER APP KIT LPC11U37 (ORYX)
• Manufacturer: Embedded Artists

Specifications of EA-APP-002

• Rohs: yes
• Product: Demonstration Kits
• Tool Is For Evaluation Of: LPC11U37
• Core: ARM Cortex M0
• Interface Type: I2C, USB
• Operating Supply Voltage: 5 V

Copyright 2012 © Embedded Artists AB
Low-power Application Kit (Oryx) - User’s Guide
the possibility to wake-up the LPC11U37 from a low-power mode. If the capacitive sensors are
completely disabled (i.e., the PCF8885 is in sleep mode) the current consumption is only 100 nA (= 0.3
uW). Since the sleep mode current consumption is so low, the chip is always powered (i.e., there is no
power switch). PIO1_15 can be used to control sleep mode of the PCF8885.
3.4.5
The board can be powered from a rechargeable Lithium coin battery (LiR2032). The board contains a
coin cell holder for the LiR2032 battery.
The Lithium battery is charged via the LTC4071 from Linear Technology, U9. It implements a shunt
battery charger system where the battery is disconnected when battery voltage is too low. The
LTC4071 allows charging of Lithium coin batteries from very low current, intermittent or continuous
charging sources. The low battery latching disconnect function protects the battery from deep
discharge and potentially irreparable damage. The disconnect level is programmable via the LBSEL
input pin. By default it is set to 2.7V (LBSEL connected to VCC). If the battery is disconnected, the
board can still operate but then power must be supplied from an external source.
There are 4 different power sources for charging the battery or for powering the board:
The LTC4071 further prevents the battery voltage from exceeding a programmed level (set via the ADJ
input pin). By default this level is set to 4.2V (ADJ connected to VCC).
The design around the LTC4071 is very flexible and alternative energy storage solutions (other than
Lithium coin batteries) can be used. Via SJ4 an external battery can be used, for example a thin-film
battery from IPS (Infinite Power Solutions). C44 is a voltage conserving capacitor in case the external
energy reserve has high internal resistance. This is typically the case when using thin-film batteries.
Current surges will create voltage dips unless C44 is properly sized. See LTC4071 datasheet for
details about operation in general and alternative energy storage solutions. The capacitance of C44
might need to be increased for other energy storage solutions.
The LTC4071 is a shunt charger that can handle up to 50 mA. With the help of R30 (the shunt
resistance, Rin) the correct charge voltage and current for the battery is created. R30 is by default 30
ohm which has been carefully selected with trade-offs between input voltage range, maximum charge
current and current consumption of the board. R30 = 30 ohm gives the following data for the charger:




 Maximum input voltage is (Ishunt_max * Rin) + Vbat_min + Vfdiode= (0.050 * 30) + 3.2 + 0.3
 Max power dissipation in R30 occurs when maximum input voltage and minimum battery
USB power from the LPC-LINK (embedded SWD/JTAG debug interface). By default this path
is enabled via JP2, pin 1-2 and D5. It can be disables as charging/powering option by
removing the jumper in JP2, pin 1-2.
USB power from the LPC11U37 USB interface. This path is always enabled via D3.
External power input from J7, pin 2. Voltage shall be 5.0V. By default this path is enabled via
JP2, pin 3-4 and D4. It can be disables as charging/powering option by removing the jumper
in JP2, pin 3-4.
for external power source to be connected. There are additional series resistors for the 10V
nominal input since the Lithium charger is designed for 5V nominal input voltage. There is
also provision (pads) for protection diodes to keep the input voltage under control, see
D11/D12 in the schematic.
= 5.0 V
voltage: (Vin_max – Vbat_min)
The board can also consume current while charging the battery. This will reduce the available
charging current, i.e., will increase charging time.
An external source, either 5V or 10V nominal. It can for example be a solar panel. J5 allow
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2
/ Rin = (5 – 0.3 – 3.2)
2
/ 30 = 75 mW
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