TOP232G Ver la hoja de datos (PDF) - Power Analog Micoelectronics

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componentes Descripción

Fabricante

TOP232G

Design Flexible, EcoSmart, Integrated Off-line Switcher

Power Analog Micoelectronics 

TOP232-234

Function

TOPSwitch-II TOPSwitch-FX Figures Advantages

Remote ON/OFF

N/A*

Single transistor 8, 19,

or optocoupler

20, 21,

interface or manual 22, 23,

switch

27

• Fast on/off (cycle by cycle)

• Active-on or active-off control

• Low consumption in remote off state

• Active-on control for fail-safe

• Eliminates expensive in-line on/off

switch

• Allows processor controlled turn on/

off

• Permits shutdown/wake-up of

peripherals via LAN or parallel port

Synchronization

N/A*

Single transistor

or optocoupler

interface

• Synchronization to external lower

frequency signal

• Starts new switching cycle on

demand

Thermal Shutdown

Latched

Hysteretic (with

70 °C hysteresis)

• Automatic recovery from thermal

fault

• Large hysteresis prevents circuit

board overheating

Current Limit Tolerance ±10% (@25 °C) ±7% (@25 °C)

-8% (0 °C to100 °C) -4% (0 °C to 100 °C)

• 10% higher power capability due to

tighter tolerance

DRAIN

Creepage at

Package

DIP 0.037" / 0.94 mm

SMD 0.037" / 0.94 mm

TO-220 0.046" / 1.17 mm

0.137" / 3.48 mm

0.137" / 3.48 mm

0.068" / 1.73 mm

• Greater immunity to arcing as a

result of build-up of dust, debris and

other contaminants

DRAIN Creepage at

PCB for TO-220

0.045" / 1.14 mm 0.113" / 2.87 mm

(preformed leads)

• Preformed leads accommodate

large creepage for PCB layout

• Easier to meet Safety (UL/VDE)

*Not available

Table 3 (cont). Comparison Between TOPSwitch-II and TOPSwitch-FX.

TOPSwitch-FX Design Considerations

TOPSwitch-FX Selection

Selecting the optimum TOPSwitch-FX depends upon required

maximum output power, efficiency, heat sinking constraints

and cost goals. With the option to externally reduce current

limit, a larger TOPSwitch-FX may be used for lower power

applications where higher efficiency is needed or minimal heat

sinking is available.

Input Capacitor

The input capacitor must be chosen to provide the minimum

DC voltage required for the TOPSwitch-FX converter to maintain

regulation at the lowest specified input voltage and maximum

output power. Since TOPSwitch-FX has a higher DCMAX than

TOPSwitch-II, it is possible to use a smaller input capacitor. For

TOPSwitch-FX, a capacitance of 2 µF per watt is usually

sufficient for universal input with an appropriately designed

transformer.

Primary Clamp and Output Reflected Voltage VOR

A primary clamp is necessary to limit the peak TOPSwitch-FX

drain to source voltage. A Zener clamp (see Figure 26, VR1)

requires few parts and takes up little board space. For good

efficiency, the clamp Zener should be selected to be at least 1.5

times the output reflected voltage VOR as this keeps the leakage

spike conduction time short. When using a Zener clamp in a

universal input application, a V of less than 135 V is

OR

recommended to allow for the absolute tolerances and

temperature variations of the Zener. This will ensure efficient

operation of the clamp circuit and will also keep the maximum

drain voltage below the rated breakdown voltage of the

TOPSwitch-FX MOSFET.

A high VOR is required to take full advantage of the wider DCMAX

of TOPSwitch-FX. An RCD clamp provides tighter clamp

voltage tolerance than a Zener clamp and allows a VOR as high

as 165 V. The VOR can be further increased in continuous mode

designs up to 185 V by reducing the external current limit as a

function of input line voltage (see Figure 18). The RCD clamp

20 B

7/01

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