Description
The RD7 reference design board is an example of a very low cost production worthy DC input standby power supply design using the TOPSwitch-II family of Three-terminal Off-line PWM switchers. The reference design board is intended to help TOPSwitch-II users quickly develop their products. It provides a basic design that can be easily modified to fit a particular application. The RD7 operates from a rectified and filtered AC mains voltage and provides 3.5 W output at 5 V. Features such as a 12 V non-isolated output or tighter output voltage tolerance may be implemented by changing only a few components.

Low Cost Production Worthy Reference Design
*Up to 3.5 W of output power
*Meets Blue Angel requirements (5 W)
*Single sided board
*Low cost through-hole components
*Fully assembled and tested
*Easy to evaluate and modify
*Extensive performance data
*Light weight - no heat sink required for TOPSwitch-II
*Non-isolated +12 V output option

Fully Protected by TOPSwitch-II
*Primary safety current limit
*Output short circuit protection
*Thermal shutdown protects entire supply

Designed for World Wide Operation
*Designed for IEC/UL safety requirements
*Designed for wide range of input voltage

Typical Applications
*Desktop PC stand-by power supply (PS98, ATX, NLX, SFX, Micro ATX)
*Consumer stand-by supply (e.g. TV, VCR, DVD)

Description
TinySwitch-II integrates a 700 V power MOSFET, oscillator, high voltage switched current source, current limit and thermal shutdown circuitry onto a monolithic device. The start-up and operating power are derived directly from the voltage on the DRAIN pin, eliminating the need for a bias winding and associated circuitry. In addition, the TinySwitch-II devices incorporate auto-restart, line under-voltage sense, and frequency jittering.
An innovative design minimizes audio frequency components in the simple ON/OFF control scheme to practically eliminate audible noise with standard taped/varnished transformer construction. The fully integrated auto-restart circuit safely limits output power during fault conditions such as output short circuit or open loop, reducing component count and secondary feedback circuitry cost. An optional line sense resistor externally programs a line under-voltage threshold, which eliminates power down glitches caused by the slow discharge of input storage capacitors present in applications such as standby supplies. The operating frequency of 132 kHz is jittered to significantly reduce both the quasi-peak and average EMI, minimizing filtering cost.

TinySwitch-II Features Reduce System Cost
*Fully integrated auto-restart for short circuit and open loop fault protection–saves external component costs
*Built-in circuitry practically eliminates audible noise with ordinary dip-varnished transformer
*Programmable line under-voltage detect feature prevents power on/off glitches–saves external components
*Frequency jittering dramatically reduces EMI (~10 dB)–minimizes EMI filter component costs
*132 kHz operation reduces transformer size–allows use EF12.6 or EE13 cores for low cost and small size
*Very tight tolerances and negligible temperature variation on key parameters eases design and lowers cost
*Lowest component count switcher solution
*Expanded scalable device family for low system cost

Better Cost/Performance over RCC & Linears
*Lower system cost than RCC, discrete PWM and other integrated/hybrid solutions
*Cost effective replacement for bulky regulated linears
*Simple ON/OFF control–no loop compensation needed
*No bias winding–simpler, lower cost transformer
*Simple design practically eliminates rework in manufacturing

EcoSmart®–Extremely Energy Efficient
*No load consumption < 50 mW with bias winding and < 250 mW without bias winding at 265 VAC input
*Meets Blue Angel, Energy Star, and EC requirements
*Ideal for cell-phone charger and PC standby applications

High Performance at Low Cost
*High voltage powered–ideal for charger applications
*High bandwidth provides fast turn on with no overshoot
*Current limit operation rejects line frequency ripple
*Built-in current limit and thermal protection improves safety

TNY263G, TNY264G, TNY265G, TNY266G, TNY267G, TNY268G,
TNY263P, TNY264P, TNY265P, TNY266P, TNY267P, TNY268P

Lower System Cost, High Design Flexibility
• Extended power range to 250 W
• Features eliminate or reduce cost of external components
• Fully integrated soft-start for minimum stress/overshoot
• Externally programmable accurate current limit
• Wider duty cycle for more power, smaller input capacitor
• Separate line sense and current limit pins on Y/R packages
• Line under-voltage (UV) detection: no turn off glitches
• Line overvoltage (OV) shutdown extends line surge limit
• Line feed forward with maximum duty cycle (DCMAX) reduction rejects line ripple and limits DCMAX at high line
• Frequency jittering reduces EMI and EMI filtering costs
• Regulates to zero load without dummy loading
• 132 kHz frequency reduces transformer/power supply size
• Half frequency option in Y/R packages for video applications
• Hysteretic thermal shutdown for automatic fault recovery
• Large thermal hysteresis prevents PC board overheating

Description
TOPSwitch-GX uses the same proven topology as TOPSwitch, cost effectively integrating the high voltage power MOSFET,
PWM control, fault protection and other control circuitry onto a single CMOS chip. Many new functions are integrated to reduce system cost and improve design flexibility, performance
and energy efficiency.
Depending on package type, the TOPSwitch-GX family has either 1 or 3 additional pins over the standard DRAIN, SOURCE and CONTROL terminals. allowing the following functions:
line sensing (OV/UV, line feedforward/DC max reduction), accurate externally set current limit, remote on/off, and synchronization to an external lower frequency and frequency selection (132 kHz/66 kHz).
All package types provide the following transparent features: Soft-start, 132 kHz switching frequency (automatically reduced at light load), frequency jittering for lower EMI, wider DCMAX,
hysteretic thermal shutdown and larger creepage packages. In addition, all critical parameters (i.e. current limit, frequency, PWM gain) have tighter temperature and absolute tolerance, to
simplify design and optimize system cost.


TOP245
TOP246

Design Highlights
• Extremely low component count
• High efficiency – 85% using Schottky rectifiers
• No current sense resistor or transformer required
• Accurate input under/over voltage meets ETSI standards
• Operates to zero load with no pre-load required
• Output overload, open loop and thermally protected
• 400 kHz operation minimizes size of magnetics

Operation
DPA-Switch greatly simplifies the design compared to a discrete implementation. Resistor R1 programs the input under/over voltages to 33 V and 86 V, respectively. Including tolerances
these thresholds guarantee the converter is operational between 36 V and 75 V, without the cost of additional line sense components.
Resistor R3 programs the internal current limit of the DPA425R to 50% of nominal. The larger DPA-Switch selection reduces conduction losses, raising efficiency without circuit changes or increased overload power.
Zener VR1 clamps leakage inductance spikes, keeping the DRAIN voltage below BVDSS. The bias supply for U1 is provided from an auxiliary flyback transformer winding.
On the secondary, a snubber across D2 (C9, R5 and R13) limits the secondary leakage inductance spikes generated by diode reverse recovery. Inductor L2, C13 and C14 form a
post-filter to reduce high frequency output switching ripple. A soft-finish network, C18, D3 and R7, eliminates output turn-on overshoot. The remaining components provide output voltage regulation and loop compensation.

Key Design Points
• For nominal under-voltage set point VUV: R1 = (VUV-2.35 V)/50μA. VOV = (R1×135 μA)+2.5 V.
• Zener VR1 voltage is 130 V to safely limit the DRAIN voltage below VDSS of 200 V.
• Opto U2 should have a CTR of between 100% and 200% for optimum loop stability.
• Set resonance of L2 and C13 + C14 to beyond loop crossover frequency (typically 5% to 10% of switching frequency).
• Good layout practices should be followed:
- Locate C5, C6 and R4 close to U1, with grounds returned to the SOURCE pin.
- Primary return should be connected to the DPA-Switch tab, not the SOURCE pin.
- Minimize the primary and secondary loop areas to reduce parasitic leakage inductance.


DPA425R

Description
TinySwitch-II maintains the simplicity of the TinySwitch topology, while providing a number of new enhancements to further reduce system cost and component count, and to practically eliminate audible noise. Like TinySwitch, a 700 V power MOSFET, oscillator, high voltage switched current source, current limit and thermal shutdown circuitry are integrated onto a
monolithic device. The start-up and operating power are derived directly from the voltage on the DRAIN pin, eliminating the need for a bias winding and associated circuitry. In addition, the
TinySwitch-II devices incorporate auto-restart, line undervoltage sense, and frequency jittering. An innovative design minimizes audio frequency components in the simple ON/OFF control scheme to practically eliminate audible noise with standard taped/varnished transformer construction. The fully integrated auto-restart circuit safely limits output power during
fault conditions such as output short circuit or open loop, reducing component count and secondary feedback circuitry cost. An optional line sense resistor externally programs a line
under-voltage threshold, which eliminates power down glitches caused by the slow discharge of input storage capacitors present in applications such as standby supplies. The operating frequency of 132 kHz is jittered to significantly reduce both the quasi-peak and average EMI, minimizing filtering cost.

Product Highlights
1. TinySwitch-II Features Reduce System Cost
  • Fully integrated auto-restart for short circuit and open loop fault protection–saves external component costs
  • Built-in circuitry practically eliminates audible noise with ordinary varnished transformer
  • Programmable line under-voltage detect feature prevents power on/off glitches–saves external components
  • Frequency jittering dramatically reduces EMI (~10 dB)
   – minimizes EMI filter component costs
  • 132 kHz operation reduces transformer size–allows use of EF12.6 or EE13 cores for low cost and small size
  • Very tight tolerances and negligible temperature variation on key parameters eases design and lowers cost
  • Lowest component count switcher solution
2. Better Cost/Performance over RCC & Linears
  • Lower system cost than RCC, discrete PWM and other integrated/hybrid solutions
  • Cost effective replacement for bulky regulated linears
  • Simple ON/OFF control–no loop compensation needed
  • No bias winding–simpler, lower cost transformer
3. EcoSmart®–Extremely Energy Efficient
  • No load consumption < 50 mW with bias winding and < 250 mW without bias winding at 265 VAC input
  • Meets Blue Angel, Energy Star, and EC requirements
  • Ideal for cell-phone charger and PC standby applications
4. High Performance at Low Cost
  • High voltage powered–ideal for charger applications
  • High bandwidth provides fast turn on with no overshoot
  • Current limit operation rejects line frequency ripple
  • Built-in current limit and thermal protection

TNY264P, TNY266P, TNY267P, TNY268P, TNY264G, TNY266G, TNY267G, TNY268G