nAN400-02 battery powered applications might desirable power supp

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nAN400-02 battery powered applications might desirable power supp

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nRF0433 power supply duty cycling
nAN400-02
battery powered applications might desirable power supply duty cycling reduce average current consumption, which means that transceiver switched communication pauses. This application note describes reduce average current consumption nRF0433 single-chip transceiver power supply duty cycling.
Circuit description
Power supply duty cycling implemented feeding power supply nRF0433 device external P-channel enhancement mode MOSFET transistor, switch power on/off controlling gate voltage transistor. gate voltage would normally controlled microcontroller port shown Figure logic transistor gate will power chip. transistor gate causes transistor open, power will connected chip. nRF0433 uses 4MHz reference signal from microcontroller.
4.7µ ON_OFF
MOSFET P-channel
100nF
TXEN
+5V_RF
micro controller
XTAL1 XTAL2
DOUT
100pF
nRF0433
5.6pF
8.2M
22pF
22pF
Figure Principal circuit diagram power duty cycling with nRF0433
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nRF0433 power supply duty cycling
speed turn-on/off cycle, base-band decoupling should done source side switching transistor. nRF0433 supply voltage (+5V_RF) should decoupled close possible pins with high performance capacitors (e.g. ceramic). transceiver used with maximum output power (10mW), switching transistor should able handle current drain about 50mA. on-resistance transistor (rDS(on)) should small possible (rDS(on) less than minimize voltage drop over transistor, minimize power dissipation (PTR rDS(on) Recommended transistors MMBF0202PLT1 (Motorola) BSH202 (Philips). reduce noise generated full swing digital data input signal, DIN, serial termination signal line included. serial termination resistor (R1) should placed close possible microcontroller port where signal generated.
Communication protocol considerations
Each communication device should start each transmission with preamble. preamble pattern reversals, 101010., repeated given period (say second). preamble then gives remote devices opportunity save battery power, because nRF0433 remote devices turned receive mode milliseconds then turned again about second preamble detected. preamble would also normally used receiving devices attain synchronization. duty-cycle, that often nRF0433 remote devices turned depends duration preamble. Increasing duration preamble means transceivers turned less frequently, average power consumption will decrease. long duration preamble depends required response time from remote devices when they polled. time from power nRF0433 device switched until synthezised frequency stable power time, ton. When external 4MHz reference signal (eg. from driver active microcontroller, shown Figure available input when powering transceiver, This means that during power receive mode, receiver receive data until pins have been stable (±5%) least 7.5ms. further details important timing data, nRF0433 datasheet, revision [1].
Battery life calculation example
example communication system consists master node which polls number remote devices their state measurement values. Each transmission from master node remote devices starts with preamble. Each remote device battery powered with 550mAh battery. battery remote devices should last about year (365 days/year year hours/day 8760 hours).
Nordic VLSI Revision:
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February 2000
nRF0433 power supply duty cycling
This means that allowed average current consumption 550mAh 62.8µA 8760 hours
During power-up receive mode, receiver susceptible data until pins have been stable (±10%) least 7.5ms. current consumption nRF0433 continuos operation receive mode typically 23mA. transceiver powered receive mode listen preamble 10ms every 3.66 seconds, average current consumption will 62.8µA 3.66
This means that each transmission should start with preamble period least 3.66 seconds. Each remote device then turned receive mode 10ms turned again about 3.66 seconds preamble detected.
References
Product specification nRF0433, "Single chip 433MHz Transceiver", Nordic VLSI ASA.
Nordic VLSI Revision:
Vestre Rosten N-7075 Tiller, Norway Page
Phone
February 2000
nRF0433 power supply duty cycling
LIABILITY DISCLAIMER
Nordic VLSI reserves right make changes without further notice product improve reliability, function design. Nordic VLSI does assume liability arising application product circuits described herein.
LIFE SUPPORT APPLICATIONS
These products designed life support appliances, devices, systems where malfunction these products reasonably expected result personal injury. Nordic VLSI customers using selling these products such applications their risk agree fully indemnify Nordic VLSI damages resulting from such improper sale.
Application Note. Revision Date 22.02.2000. Application Note order code 220200-nAN400-02 rights reserved Reproduction whole part prohibited without prior written permission copyright holder.
Nordic VLSI Revision:
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February 2000
nRF0433 power supply duty cycling
YOUR NOTES
Nordic VLSI Revision:
Vestre Rosten N-7075 Tiller, Norway Page
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nRF0433 power supply duty cycling
Nordic VLSI World Wide Distributors
Your nearest dealer, please http://www.nvlsi.no
Main Office: Vestre Rosten N-7075 Tiller, Norway Phone: Fax: E-mail: nRF@nvlsi.no Visit Nordic VLSI website http://www.nvlsi.no
Revision:
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February 2000

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