MIC204 datasheet(14/15 Pages) MICREL

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MIC2044/2045

Micrel

MIC2044/2045

October 2003

7,11,

13,16

9,12,14

RSET

200W

0.1mF

MIC2044-1BTS

VBIAS

VIN

/FAULT

UVLOIN

SLEW

VOUT

PGREF

PWRGD

ILIM

GND

47kW

75kW

36.5kW

CLOAD

22mF

VOUT

0.8V @1.5A

47kW

Digital

Output

Signals

10mF

0.1mF

VIN

0.8V

VDD

2.5V

95.3kW

59.0kW

47kW

Note:

All VIN pins (7, 11, 13, 16) must be externally tied together.

All VOUT pins (9, 12, 14) must be externally tied together.

Undervoltage Lockout = 0.6V.

Output Power-Good = 0.7V.

Figure 4. Lower UVLO Setting

Power Dissipation

Power dissipation depends on several factors such as the

load, PCB layout, ambient temperature, and package type.

The following equations can be used to calculate power

dissipation and die temperature.

Calculation of power dissipation can be accomplished by the

following equation:

D = RDS(on) × (IOUT)

(5)

To relate this to junction temperature, the following equation

can be used:

J = PD × R(

θJ-A) + TA

(6)

where T

J = junction temperature, TA = ambient temperature

and Rθ(J-A) is the thermal resistance of the package.

Printed Circuit Board Hot Plug

The MIC2044/45 are ideal inrush current limiting power

switches suitable for hot plug applications. Due to the inte-

grated charge pump, the MIC2044/45 present a high imped-

ance when in the off state and the device slowly becomes a

low impedance as it turns on. This effectively isolates power

supplies from highly capacitive loads by reducing inrush

current during hot plug events. This same feature also can be

used for soft-start requirements.

PCB Layout Recommendations

The MIC2044 and MIC2045 have very low on-resistance,

typically 20m

Ω, and the switches can provide up to 6A of

continuous output current. Under heavy loads, the switched

current may cause the devices to heat up considerably. The

following list contains some useful suggestions for PCB

layout design of the MIC2044/45 in order to prevent the die

from overheating under normal operating conditions.

1. Micrel Semiconductor does not assume responsibility for the use of

this program tool in the event that any PCB assembled, tested,

produced, and/or manufactured becomes damaged and/or causes any

degradation of system performance or damage to any system

components in which the aforementioned PCB is included.

1. Supply additional copper area under the device

to remove heat away from the IC.

See

“Application Hint 17” for a general guideline

in calculating the suggested area.

2. Provide additional pad area on the corner pins of

the MIC2044/45 IC for heat distribution.

3. Tie the common power pins (V

IN = pins 7, 11,

13, 16 and V

OUT = pins 9, 12, 14) together in a

manner such that the traces entering and

leaving the device have a uniform width suffi-

cient for the application’s current requirements

plus added margin (25% minimum recom-

mended).

Ex: For 4A maximum current, design traces for

5A capability.

4. For PCB trace width calculation, there are

numerous calculator programs available on the

internet and elsewhere. As a general rule of

thumb, 15-20 mils width for every 1A of current

when using 1oz. copper. However, the trace

width calculators often take into account maxi-

mum temperature increase constraints, as well

as layer arrangement, in determining the PCB

trace widths. As a reference, the following link is

suggested for trial tests in PCB trace width

calculations.1

http://www.aracnet.com/cgi-usr/gpatrick/trace.pl

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