MAX5023 Просмотр технического описания (PDF) - Maxim Integrated

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MAX5023

65V, Low-Quiescent-Current, High-Voltage Linear Regulators with µP Reset and Watchdog Timer

Maxim Integrated 

65V, Low-Quiescent-Current, High-Voltage Linear

Regulators with µP Reset and Watchdog Timer

Example 1:

TA = +95°C

VIN = +14V

VOUT = +5V

Find the maximum allowable output current. First calcu-

late package dissipation at the given temperature as

follows:

PD = 1.538W - (0.01923W/°C) (95°C - 70°C)

= 1.057W

Then determine the maximum output current:

(1.057W)

IOUT(MAX) = (14V) - (5V) = 117.4mA

Example 2:

TA = +125°C

VIN = +14V

VOUT = +3.3V

Calculate package dissipation at the given temperature

as follows:

PD = 1.538W - (0.01923W/°C) (125°C - 70°C)

= 480.4mW

And establish the maximum current:

(480.4mW)

IOUT(MAX) = (14V) - (3.3V) = 44.89mA

Example 3:

TA = +50°C

VIN = +14V

VOUT = +5V

Calculate package dissipation at the given temperature

as follows:

PD = 1.538W

And find the maximum output current:

(1.538W)

IOUT(MAX) = (14V) - (5V) = 170.9mA ⇒IOUT(MAX) = 150mA

MAXIMUM OUTPUT CURRENT

vs. INPUT VOLTAGE

0.16

VOUT = +5V

0.14

DEVICE EXPOSED

PAD SOLDERED TO

0.12

1IN2 COPPER ISLAND

0.10

TA = +70°C

0.08

TA = +85°C

0.06

0.04

0.02

TA = +125°C

0

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

VIN (V)

Figure 6. Maximum Output Current vs. Input Voltage

In Example 3, the maximum output current is calculated

as 170.9mA, however, the maximum output current

cannot exceed 150mA. Use Figure 6 to quickly deter-

mine allowable maximum output current for selected

ambient temperatures.

Capacitor Selection and Regulator

Stability

For stable operation over the full temperature range

and with load currents up to 150mA, use a 15µF (min)

output capacitor with an ESR < 0.5Ω. To reduce noise

and improve load-transient response, stability, and

power-supply rejection, use larger output capacitor val-

ues such as 22µF.

Some ceramic dielectrics exhibit large capacitance

and ESR variation with temperature. For dielectric

capacitors such as Z5U and Y5V, use 22µF or more to

ensure stability at temperatures below -10°C. With X7R

or X5R dielectrics, 15µF should be sufficient at all oper-

ating temperatures. For high-ESR tantalum capacitors

use 22µF or more to maintain stability. To improve

power-supply rejection and transient response use a

minimum 10µF capacitor between IN and GND.

______________________________________________________________________________________ 11

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