MIC5206

Micrel

January 2000

7

MIC5206

Resistor values are not critical because ADJ (adjust) has a

high input impedance, but for best results use resistors of

470k

Ω or less. A capacitor from ADJ to ground provides

greatly improved noise performance.

1

2

3

4

8

7

6

5

2.2µF

Flag Output

(optional)

47k

R1

R2

MIC5206BMM

470pF

ADJ

Figure 3. Ultra-Low-Noise

Adjustable Voltage Application

Figure 3 also includes a 470pF capacitor for lowest-noise

operation and shows EN (pin 7) connected to IN (pin 8) for an

application where enable/shutdown is not required. C

2.2

µF minimum. The error flag is shown with a 47kΩ pullup

resistor.

Thermal Considerations

Layout

The MIC5206-x.xBM5 (5-lead SOT-23 package) has the

following thermal characteristics when mounted on a single

layer copper-clad printed circuit board.

Multilayer boards having a ground plane, wide traces near the

pads, and large supply bus lines provide better thermal

conductivity.

PC Board

θθθθθ

JA

Dielectric

FR4

220

°C/W

Ceramic

200

°C/W

SOT-23-5 Thermal Characteristics

The “worst case” value of 220

°C/W assumes no ground

plane, minimum trace widths, and a FR4 material board.

The MIC5206-xxBMM (8-lead MSOP) has a thermal resis-

tance of 200

°C/W when mounted on a FR4 board with

minimum trace widths and no ground plane.

PC Board

θθθθθ

JA

Dielectric

FR4

200

°C

MSOP Thermal Characteristics

Nominal Power Dissipation and Die Temperature

The MIC5206-x.xBM5 at a 25

°C ambient temperature will

operate reliably at over 450mW power dissipation when

mounted in the “worst case” manner described above. At an

ambient temperature of 40

°C, the device may safely dissi-

pate over 380mW. These power levels are equivalent to a die

temperature of 125

°C, the maximum operating junction tem-

perature for the MIC5206.

For additional heat sink characteristics, please refer to Micrel

Application Hint 17, “Calculating P.C. Board Heat Sink Area

For Surface Mount Packages”.