MIC2954 Просмотр технического описания (PDF) - Micrel

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MIC2954

250mA Low-Dropout Regulator

Micrel 

Micrel, Inc.

* See Application Information

Figure 1. /Error Output Timing

or about 0.01µF. When doing this, the output capacitor

must be increased to 3.3µF to maintain stability. These

changes reduce the output noise from 430µV to

100µVrms for a100kHz bandwidth at 5V output. With the

bypass capacitor added, noise no longer scales with

output voltage so that improvements are more dramatic

at higher output voltages.

Automotive Applications

The MIC2954 is ideally suited for automotive applica-

tions for a variety of reasons. It will operate over a wide

range of input voltages with very low dropout voltages

(40mV at light loads), and very low quiescent currents

(75µA typical). These features are necessary for use in

battery powered systems, such as automobiles. It is a

“bulletproof” device with the ability to survive both

reverse battery (negative transients up to 20V below

ground), and load dump (positive transients up to 60V)

conditions. A wide operating temperature range with low

temperature coefficients is yet another reason to use

these versatile regulators in automotive designs.

MIC2954

Thermal Calculations

Layout Considerations

The MIC2954-07BM/-08BM (8-pin surface-mount pack-

age) has the following thermal characteristics when

mounted on a single layer copper-clad printed circuit

board.

PC Board Dielectric Material

θJA

FR4

160°C/W

Ceramic

120°C/W

Multilayer boards having a ground plane, wide traces

near the pads, and large supply bus lines provide better

thermal conductivity.

Our calculations will use the “worst case” value of

160°C/W, which assumes no ground plane, minimum

trace widths, and a FR4 material board.

Pad Layout (minimum recommended geometry)

Nominal Power Dissipation and Die Temperature

The MIC2954-07BM/-08BM at a 55°C ambient temp-

erature will operate reliably at up to 440mW power

dissipation when mounted in the “worst case” manner

described above. This power level is equivalent to a die

temperature of 125°C, the recommended maximum

temperature for nonmilitary grade silicon integrated

circuits.

September 2007

11

M9999-090607

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