MIC5250

Micrel

March 2000

9

MIC5250

Since the total power dissipation allowable is 325mW, the

maximum power dissipation of the second regulator is limited

to:

PP

P

DD

D

(max)

(reg1)

(reg2)

=+

325mW

180.4mW

=+ P

D reg

()

2

P

D reg

()

The maximum output current of the second regulator can be

calculated using the same equations but solving for the

output current (ground current is constant over load and

simplifies the equation):

PV

V

I

V

I

D reg

IN

OUT

OUT

IN GND

()

()

+

144.6mW

4.2V

3.0V

4.2V 100 A

=−

()

+×

µ

I

OUT

I

The second output is limited to 120mA due to the total power

dissipation of the system when operating at 60

°C ambient

temperature.

Fixed Regulator Applications

INA

OUTA

BYPA

GNDA

OUTB

BYPB

GNDB

ENA

INB

ENB

3.3V

3.3V

MIC5250-3.3BMM

0.01

µF

1

µF

0.01

µF

1

µF

10

1

3

8

4

6

2

9

7

5

Figure 1. Ultra-Low-Noise Dual 3.3V Application

Figure 1 includes 0.01

µF capacitors for low-noise operation

and shows EN (pin 3) connected to IN (pin 1) for an applica-

tions where enable/shutdown is not required. C

minimum.

INA

OUTA

BYPA

GNDA

OUTB

BYPB

GNDB

ENA

INB

ENB

3.3V

3.3V

MIC5250-3.3BMM

1

µF

1

µF

10

1

3

8

4

6

2

9

7

5

Figure 2. Low-Noise Fixed Voltage Application

Figure 2 is an example of a low-noise configuration where

C

Dual-Supply Operation

When used in dual supply systems where the regulator load

is returned to a negative supply, the output voltage must be

diode clamped to ground.