MAX5091 データシートの表示（PDF） - Maxim Integrated

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MAX5091

28V, 100mA, Low-Quiescent-Current LDO with Reset and Power-Fail Input/Output

Maxim Integrated 

MAX5091

28V, 100mA, Low-Quiescent-Current LDO

with Reset and Power-Fail Input/Output

Applications Information

Available Output Current Calculation

The MAX5091 high-voltage regulator provides up to

100mA of output current. The input voltage extends to

+28V. Package power dissipation limits the amount of

output current available for a given input/output voltage

and ambient temperature. Figure 2 depicts the maximum

power dissipation curve for the 8-pin SO-EP package.

The graph assumes that the exposed metal back of the

MAX5091 package is soldered to copper on a single layer

PCB according to the JEDEC51 standard.

Use Figure 2 to determine the allowable package dissi-

pation for a given ambient temperature. Alternately, use

the following formula to calculate the allowable package

dissipation:

PD

=



1.538

−

1.538W for TA ≤

0.01923 (TA − 70°C) For

+ 70°C

+ 70°C

<

TA

≤

+



125°C

2.0

1.8

1.6

1.538W

8-PIN SO-EP

1.4

DERATE

1.2

19.23mW/°C

1.0

0.8

0.6

0.4

0.2

0

10 30 50 70 90 110 130 150

20 40 60 80 100 120 140

TEMPERATURE (°C)

Figure 2. 8-Pin SO-EP Maximum Power Dissipation vs.

Temperature

After determining the allowable package dissipation,

calculate the maximum output current using the following

formula:

IOUT(MAX)

≅

VS

PD

− VOUT

The above equations do not include the power dissipation

from self-heating due to the IC ground current.

The junction-to-ambient thermal impedance depends

on the area of the copper plane, its thickness, and the

number of copper layers on PCB. For the higher power

dissipation requirement, use multiple-layered PCBs with

2oz copper and a large copper area.

Capacitor Selection and Regulator Stability

For stable operation over the full temperature range

and with load currents up to 100mA, use a 10μF output

capacitor with a low ESR. Table 1 shows a list of recom-

mended output capacitor ESR for various load conditions.

Table 1. Recommended Output Capacitor

ESR

RECOMMENDED COUT ESR

IOUT

VOUT = 3.3V

VOUT = 5.0V

IOUT ≤ 10mA

CESR < 0.66Ω

CESR < 1Ω

IOUT ≤ 50mA

CESR < 0.132Ω

CESR < 0.2Ω

IOUT ≤ 100mA

CESR < 66mΩ

CESR < 0.1Ω

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