MC33166 データシートの表示（PDF） - ON Semiconductor

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MC33166

3.0 A, Step−Up/Down/Inverting Switching Regulators

ON Semiconductor 

MC34166, MC33166

equivalent Schottky barrier rectifier is recommended to fulfill

these requirements.

Undervoltage Lockout

An Undervoltage Lockout comparator has been

incorporated to guarantee that the integrated circuit is fully

functional before the output stage is enabled. The internal

5.05 V reference is monitored by the comparator which

enables the output stage when VCC exceeds 5.9 V. To prevent

erratic output switching as the threshold is crossed, 0.9 V of

hysteresis is provided.

Thermal Protection

Internal Thermal Shutdown circuitry is provided to protect

the integrated circuit in the event that the maximum junction

temperature is exceeded. When activated, typically at 170°C,

the latch is forced into a ‘reset’ state, disabling the output

switch. This feature is provided to prevent catastrophic

failures from accidental device overheating. It is not

intended to be used as a substitute for proper heatsinking.

The MC34166 is contained in a 5−lead TO−220 type package.

The tab of the package is common with the center pin (Pin 3)

and is normally connected to ground.

DESIGN CONSIDERATIONS

Do not attempt to construct a converter on wire−wrap

or plug−in prototype boards. Special care should be taken

to separate ground paths from signal currents and ground

paths from load currents. All high current loops should be

kept as short as possible using heavy copper runs to minimize

ringing and radiated EMI. For best operation, a tight

component layout is recommended. Capacitors CIN, CO, and

all feedback components should be placed as close to the IC

as physically possible. It is also imperative that the Schottky

diode connected to the Switch Output be located as close to

the IC as possible.

+

Error

100 mA

Amp

120

Compensation 5

1

R1

I = Standby Mode

Figure 16. Low Power Standby Circuit

+

Error

100 mA

Amp

120

Compensation 5

1

R1

VShutdown = VZener + 0.7

Figure 17. Over Voltage Shutdown Circuit

+

Error

100 mA

Amp

1

120

Compensation 5

D2

D1

R1

Vin

1.0 M

Css

tSoft−Start ≈ 35,000 Css

Figure 18. Soft−Start Circuit

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8

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