Prototype
Description
Each cup is to have its own power supply and must stay operational for two hours. The cup must NOT drive the power line of the HIU’s CANbus connection. Due to the fact that there are 4 devices to power, the most economical battery option is to use 9Volt batteries. 9Volt batteries have a maximum discharge at around 150mA continuous. Given this, each device will need more than one 9V battery wired in parallel to match the current needs of the system. Because the majority of the cup runs on a 3.3V level there would be great power loss in using a linear voltage regulator, instead the cup will utilize a 3.3V switching regulator to maximize efficiency. I have chosen to use a linear voltage regulator for the 5V line because the datasheet for the RFID reader says that it has problems being fed by a switching regulator. For further safety measures, there is a 3.6V Zener diode on the 3.3V line and a 5.1V Zener on the 5V line in case of regulator failure. The cup’s estimated to pull 120mA at 5V and 330mA at 3.3V at maximum.
Features of parts
Features of LM2675
- 3.3V switching regulator
- Efficiency up to 96%
- Available in 8-pin SOIC
- Requires Only 5 External Components
- Min input voltage 6.5V
- Max input voltage 40V
- Output voltage 3.3V fixed
- Output current 1A
- Switching frequency 260kHz
We are using a switching regulator to increase efficiency.
Features of U9VL-J-P 9V Li battery
- Average voltage 9V
- Max continuous current 150mA
- Nominal capacity 1200mA
- Battery life at max continuous discharge of 8 hours
- Pulse capability 1050mA
- Max continuous power 1350mW
The decision to use 9V batteries is purely economic.
Features of LM340-N
- Standard 3-Terminal Positive Regulator
- Fixed 5V output voltage
- Max output current 1A
- Min input voltage 7.5V
- Load regulation 50mV
- Line regulation 50mV
- Requires a capacitor on input of 0.22uF
- Optional capacitor on output of 0.1uF
Given that only CANbus will use 5V and the much closer voltages, I have chosen to use a linear voltage regulator for this portion.
Circuit diagram
Figure 1: Typical application of switching regulator
Figure 2: Typical application of linear regulator
UltiBoard Layout
Schematic used to generate UltiBoard layout
Block diagram
Prototype Testing
Figure 1: Time dependent input signal from 9V battery
Used 3 9V batteries. Total current draw 330mA
Figure 2: 3.3V output voltage
R=10Ohms I=360mA
Figure 3: 5V output voltage
R=39Ohms I=115mA
References
1. Discrete Semiconductors, “BZX84 series Voltage regulator diodes,” BZX84-A3V6,215 Datasheet, Apr. 2003.
2. Discrete Semiconductors, “PLVA6xxA series Low-voltage avalanche regulator diodes,” PLVA6xxA datasheet, May 1999.
3. On Semiconductor, “MC7800, MC7800A, MC7800AE, NCV7800,” MC7800 datasheet, May 2013.
4. Texas Instruments, “ADJUSTABLE AND FIXED LOW-DROPOUT VOLTAGE REGULATOR,” TLV1117 Datasheet, Dec. 2004April 2013.
5. Texas Instruments, “LM340-N/LM78XX Series 3-Terminal Positive Regulators,” LM340-N datasheet, April 2013.
6. Texas Instruments, “LM2675 SIMPLE SWITCHER ® Power Converter High Efficiency 1A Step-Down Voltage Regulator,” LM2675 datasheet, June 2005.
7. UltraLife, “U9VL-J-P Technical Datasheet,” U9VL-J-P datasheet, Mar. 2013.
8. Vishay, “Surface Mount Multilayer Ceramic Chip Capacitors for Commodity Applications,” VJ....W1BC datasheet, Mar. 2013.
9. Texas Instruments, “POSITIVE-VOLTAGEREGULATORS,” uA78M00 datasheet, May 2013.
10. Panasonic, “NICKEL METAL HYDRIDE BATTERIES: INDIVIDUAL DATA SHEET,” HHR120AA datasheet, Aug. 2005.
11. Vishay, “Schottky Barrier Rectifier,” SB120 thru SB160 datasheet, Oct. 2009.
12. Panasonic, “Aluminum Electrolytic Capacitors,” Capacitor datasheet, Jul. 2008.
13. Vishay, “Zener Diodes,” BZX85 datasheet, Nov. 2011.
14 TDK, “C3216X5R1A107M160AC,” C3216X5R1A107M160AC datasheet, Sep. 2013.
15. Bourns, “SRN6045 Series - Semi-shielded Power Inductors,” SRN6045 datasheet, Aug. 2013.
16. Vishay, “Surface Mount Multilayer Ceramic Chip Capacitors for Commercial Applications,” VJ Commercial Series datasheet, May 2013.