Power Supply Design

For 90-264VAC should consider one of these wall warts:
15W 5V/2.6A Universal Power Supply - $9.95 @ Circuit Specialists
Wall Adapter Power Supply - 5VDC 1A - $5.95 @ sparcfun

If a PCB version is absolutely required (for size and connections) consider this one:
Digikey 102-1470-ND - 5V/1A Universal AC Input; $19.96

After studying the design, I think that there should be two designs; non-isolated DC and isolated AC. The MAX5033 (7.5V - 76V) or TL2575HV (4.75V - 60V) are the best bet for DC. These devices are super simple and support most applications (9-12V wall wart) as well as UPS/telecom (24V - 76V) applications. One of the others should then be used to create an isolated AC 90V - 265V power supply. Isolated AC supplies are slightly more complicated requiring a transformer, opto-isolator, careful component selection (for safety and longevity), as well as careful PCB layout. The AC version could prove to be the most widely used if done right because it will only be slightly more expensive than the DC version and will not require a relatively expensive wall wart. UL, CE, and EU certifications might be a problem though for someone wanting to sell them.

Selection

7-40V DC Input; 1A SMPS

• LM2595T-ADJ - $3.85; 1.2V-40V in; adj out; 1A; smaller inductor and caps (150KHz)

I decided to use the adjustable version. It is really easy to use a fixed version by installing 0 ohm for the one of the adjustment resistors. This is primairly so that I can change between 5V and 3.3V VCC voltages if needed. Many parts are starting to come with 3.3V (e.g. XBee)

• Adj Resistors Selection
  • (1% metal film)
  • R1 range 240 - 1.5k; lower is better
  • R2 = R1 * ((Vout / 1.23V) - 1)
  • 5V: R1 = 976; R2 = 3.00k; 0.28% error
  • 3.3V: R1 = 1.07k; R2 = 1.80k; 0.04% error
  • Use this spreadsheet to find resistor ratios: ResistorRatios_v2.xls
• Inductor Selection
  • I graphed the formula in the datasheet for Vo = {3.3, 5} over Vi = 0-40V. The highest E*T occurs at the highest input voltage, 40V. For Vin=40 I calculated that E*T is 23 @ 3.3V and 32 @ 5V. From the data sheet, I need 68uH/L30 @ 3.3V/1A and 100uH/L29 @ 5V/1A.
  • At 1A output the inductor current will be 1.350A
  • SP-1207-101M - $1.25; shielded; surface mount; 100uH/1.7A
  • SP-1207-101M - $1.25; shielded; surface mount; 68uH/2.1A
  • CWS - Excellent mfg direct coils; $10 minimum order
• Output Capacitor
  • 220uF/10V - AVX TPS Series or Sprague 595D Series
  • 80-T491D227K010 Mouser - $1.40; tantalum; 10V; 220uF;
• Feedforward Capacitor
  • 4.7nF
  • Not ceramic Z5U material
  • 581-CF012D0472J Mouser - $0.46; 4.7nF; 5%; 50V
• Catch Diode
  • Schottky
  • 1.3 x max current (1.3*1.0=1.30A)
  • 1.25 x max input voltage (1.25*40=50V)
  • MBRS160/10BQ050/10MQ060
  • 512-SS26 Mouser - $0.40; 2A; 60V; Schottky
• Input Capacitor
  • Voltage: 1.25 x max input voltage (1.25*40=50V)
  • RMS Current: 0.5 x max output current (0.50*1.2=600mA)
  • 120-220uF
  • 647-UUD1H221MNL Mouser - $0.90; Low Impedance SMD Aluminum Electrolytic; 220uF; 50V

7-15V DC Input; 800mA Linear

• Regulator IC
  • MC33269DTRK (DPack/T0-252 package) - (MC33269DT-5.0) (has 20V maximum input)
  • TI: TLV1117 (KVU/TO-252 package) - $0.96 (TLV1117-50CKVURG3) or (TLV1117-33CKVURG3)
  • ST: LD1117 - $0.78
• Could use the adjustable version then select 3.3 vs 5V w/ resistors
  • Vo=Vref*(1+(R2/R1))+(Iadj*R2); Vref=1.25V; Iadj=80uA
  • Same formula as SMPS above: R2=R1*((Vo/Vr)-1)
  • 5V: R1 = 1.00k; R2 = 3.00k; 0.00% error
  • 3.3V: R1 = 976; R2 = 1.60k; 0.04% error
• Diode on Vin (for reverse protection) eliminates need for diode across the part
• Cout: 100uF/10V
• Cin: 10uF/25V

Approach

The main PIC board should have both a standard 7805/7805LDO footprint and a TL2575HV/MAX5033 footprint. This will allow flexibility when populating the board w/o requiring much additional real estate.

Both of the battery powered boards should be provided on a separate board that can stack onto the common processor board. One battery board will be for low power applications and use AA batteries w/ a step up SMPS controller. The other battery board will be a rechargeable Li w/ a Li charger and step up SMPS controller.

The isolated AC version should be provided on a separate board that can stack onto the common processor board. This is primairly because a PS like that will come in handy for many projects and because I don't initially plan to take the time to design the layout. It will wait until I have a number of other modules created.

Offline

MAX5021/MAX5022 - 90-265v to 5V @ 1A; isolated
UCC3888 - 400-100V to 5V @ 200mA; non-isolated
UCC3809-2 off-line; isolated

Wide DC Input

• LM5575 - $5.10; 6V-75V; 1.5A; adj output; High frequency; same design and footprint at 42V volt LM75575
• TL2575HV-ADJ - 4.75V - 60V input; adjustable output; 1A; simple; $2.50-HV; $1.75 std
  • This part will need different inductors for various input voltages vs. expected output current. It is probably not all that good on the top voltage end with low currents.
  • Needs large capacitors because of the low 52KHz frequency
• MAX5033 - One part 7.5V to 76V; adjustable output; 500mA; simple
  • This part is not stocked by DigiKey
  • Has better low current performance
  • Needs smaller caps <100uF
• LM5010 - 8V-75V input; 1A; adjustable output; $4.50 @ DigiKey

Medium DC Input

• LM25575 - $4.05; 6V-42V; 1.5A; adj output; High frequency; same design and footprint at 75V volt LM5575
• LM5575 - $4.00; 6V-75V; 1.5A; adj output; High frequency; same design and footprint at 42V volt LM75575
• TL2575-ADJ - 4.75V - 40V input; adjustable output; 1A; simple; $1.50
• LM2595T-ADJ - $3.85; 1.2V-40V in; adj out; 1A; smaller inductor and caps (150KHz)
• L5970D - $3.50; 4.4V-36V in; adj out; 1A; Small caps (250KHz)
  • App note w/ layout
• LM3478 - $2.62; Nice but needs external IRF7807 @ ~$2; a few more parts but easy to make a 3V-24V in / 5V 1A out supply
• LM3489 - $1.77; 4.5V-35V input; Adj out; Needs FDC5614P @ $0.98 for 500mA out

-48V Telecom

MAX5021/MAX5022 - 38-72v to 5V @ 1A; isolated
Designing Compact Telecom Power Supplies - Uses MAX5021

Support both AC and DC from one chip layout

Might be different parts, but same board layout is likely possible
MAX5068
MAX5052-MAX5053

Battery Based w/ Li Charger

To Be Chosen - switching supply for AA batteries

• LTC4088 - $4.40; USB or wall cube input; single cell Li battery charger; both 5V and 3.3V output; no boost
• LM3658B - $1.92; USB or wall cube input; single cell Li battery charger; NO REGULATOR
• bq2403x - $4; Dual input; single cell Li charger and power selector; no boost
• TPS6300 - $4.50; buck-boost 5.5V-1.8V input; 5V or 3.3V output @1A; good for use with Li packs and chargers
• Microchip MCP73833

Battery Based w/ NiMh Charger

• Battery Fast Charge Controllers

Battery Based w/o Charger

• LM2703 - $2.23; 2.2V-6V in; adj out; >100mA
• LM2704 - $2.65; 2.2V-7V in; adj out; 120mA @ 5V
• LM2621 - $1.98; 1.2V-14V in; adj out; 500mA @ 5V
• LM2733 - $2.58; 2.7V-14V in; adju out; designed for higher voltage output (30V) for LED drives
• TPS61202 - $3.90; 0.5V-5.5V in; adj out; 300mA @ 3.3 600ma @ 5V

Reverse Polarity Protection

FET Supplies Low-Voltage Reverse-Polarity Protection - Use a pchannel FET like a dual IRF7342 FET; drain to the power source; source to the load; and gate to ground