MAX5084ATT+T Datasheet MAX5085ATT+T, MAX5084ATT+T | P7-P9

Detailed Description

The MAX5084/MAX5085 are high-voltage linear regula-

tors with a 6.5V to 65V input voltage range. The devices

guarantee 200mA output current and are available with

preset output voltages of 3.3V or 5V. Both devices can

be used to provide adjustable outputs from 2.54V to

11V by connecting a resistive divider from OUT to SET

to GND. Thermal shutdown and short-circuit protection

are provided to prevent damage during overtempera-

ture and overcurrent conditions. An output sense pin

(OUT_SENSE) provides for Kelvin sensing of the output

voltage, thereby reducing the error caused by internal

and external resistances. An enable input (EN) allows

the regulators to be turned on/off through a logic-level

voltage. Driving EN high turns on the device, while dri-

ving EN low places the device in a low-power shut-

down mode. In shutdown, the supply current reduces

to 6µA (typ). Both devices operate over the -40°C to

+125°C temperature range and are available in a 3mm

x 3mm, 6-pin TDFN package capable of dissipating

1.905W at T

= +70°C.

Regulator

The regulator accepts an input voltage range from 6.5V

to 65V. The MAX5084/MAX5085 offer fixed-output volt-

ages of 5V and 3.3V, respectively. The output voltage is

also adjustable from 2.54V to 11V by connecting an

external resistive divider network between OUT, SET,

and GND (see R1 and R2 in Figure 2). The MAX5084/

MAX5085 automatically determine the feedback path

depending on the voltage at SET.

Enable Input (EN)

EN is a logic-level enable input, which turns the

MAX5084/MAX5085 on/off. Drive EN high to turn on the

device and drive EN low to place the device in shut-

down. When in shutdown, the MAX5084/MAX5085 typi-

cally draw 6µA of supply current. EN can withstand

voltages up to 65V, allowing EN to be connected to IN

for an always-on operation. EN has an internal 5MΩ

resistor to GND.

Remote Sensing (OUT_SENSE)

OUT_SENSE provides for Kelvin sensing of the fixed

output voltage, thus eliminating errors due to the volt-

age drop in the trace resistance between OUT and the

load. OUT_SENSE is internally connected to OUT

through a 15Ω resistor (Figure 1), and can be left float-

ing when remote sensing is not required. However, if

accurate output voltage regulation at the load is

required, then connect OUT_SENSE directly to the load.

Thermal Protection

When the junction temperature exceeds +160°C, an

internal thermal sensor signals the shutdown logic to

turn off the pass transistor and allows the IC to cool.

The thermal sensor turns the pass transistor on again

after the junction temperature cools by 10°C. This

results in a cycled output during continuous thermal

overload conditions. Thermal protection protects the

MAX5084/MAX5085 in the event of fault conditions. For

continuous operation, do not exceed the maximum

junction temperature rating of +150°C.

Output Short-Circuit Current Limit

The MAX5084/MAX5085 feature a 340mA current limit.

The output can be shorted to GND for an indefinite

period of time without damage to the device. During a

short circuit, the power dissipated across the pass tran-

sistor can quickly heat the device. When the die tem-

perature reaches +160°C, the MAX5084/MAX5085 shut

down and automatically restart after the die temperature

cools by 10°C. This results in a pulsed output operation.

Applications Information

Output Voltage Setting

The MAX5084/MAX5085 feature Dual Mode

opera-

tion: they operate in either a preset output voltage

mode or an adjustable output voltage mode. Connect

SET to GND for preset output voltage operation. In pre-

set mode, internal feedback resistors set the MAX5084’s

internal linear regulator to 5V, and the MAX5085’s inter-

nal linear regulator to 3.3V. In adjustable mode, select

an output from 2.54V to 11V using a resistive divider

(see R1 and R2 in Figure 2) connected from OUT to

SET to GND. In adjustable mode, first select the resis-

tor from SET to GND (R2) in the 1kΩ to 100kΩ range.

The resistor from OUT to SET (R1) is then calculated

by:

where V

SET

= 1.251V.

Available Output Current Calculation

The MAX5084/MAX5085 provide up to 200mA of con-

tinuous output current. The input voltage extends to

65V. Package power dissipation limits the amount of

output current available for a given input/output volt-

age and ambient temperature. Figure 3 depicts the

maximum power dissipation curve for these devices.

RRx

OUT

SET

12 1 =−

⎛

⎝

⎜

⎞

⎠

⎟

MAX5084/MAX5085

65V, 200mA, Low-Quiescent-Current

Linear Regulators in TDFN

_______________________________________________________________________________________ 7

Dual Mode is a trademark of Maxim Integrated Products, Inc.

MAX5084/MAX5085

Use Figure 3 to determine the allowable package dissi-

pation for a given ambient temperature. Alternately, use

the following formula to calculate the allowable pack-

age dissipation:

After determining the allowable package dissipation,

calculate the maximum output current using the follow-

ing formula:

The above equations do not include the negligible

power dissipation from self-heating due to the device’s

ground current.

Example 1:

= +85°C

= 14V

OUT

= 5V

Find the maximum allowable output current. First calcu-

late package dissipation at the given temperature as

follows:

= 1.905W – 0.0238W/°C (85°C – 70°C) = 1.548W

Then determine the maximum output current:

Example 2:

= +125°C

= 14V

OUT

= 3.3V

Calculate package dissipation at the given temperature

as follows:

= 1.905W – 0.0238W/°C (125°C – 70°C) = 596mW

And establish the maximum output current:

Example 3:

= +50°C

= 9V

OUT

= 5V

OUT MAX()

−

596

14 3 3

OUT MAX

()

−

1 548

14 5

172

OUT(MAX)

– V

OUT

≤ 200mA

W for T C

W W C x T C for C T C

.–. / ( )

≤+ °

°−°+°<≤+°

⎧

⎨

⎩

⎫

⎬

⎭

1 905 70

1 905 0 0238 70 70 125

65V, 200mA, Low-Quiescent-Current

Linear Regulators in TDFN

8 _______________________________________________________________________________________

= 6.5V

TO 65V

OUT

= 2.5V TO 11V

(200mA)

10μF

OUT

OUT_SENSE

SET

LOAD

GND

MAX5084

MAX5085

Figure 2. Adjustable Output Voltage Operation

MAX5084 fig03

TEMPERATURE (°C)

(W)

20 40 60 80 100 120 140-20 0

0.6

0.4

0.2

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

-40

MAXIMUM POWER

1.905W

DERATE

23.8mW/°C

Figure 3. Calculated Maximum Power Dissipation vs.

Temperature

Calculate package dissipation at the given temperature

as follows:

= 1.905W

Find the maximum output current:

In example 3, the maximum output current is calculated

as 476mA, however, the maximum output current can-

not exceed 200mA.

Alternately, use Figure 4 to quickly determine allow-

able maximum output current for selected ambient

temperatures.

Output Capacitor Selection and

Regulator Stability

For stable operation over the full temperature range

and with load currents up to 200mA, use a 10µF (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 variations 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, 10µF 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.

mA I mA

OUT MAX OUTMAX()

( )=

−

1 905

476 200

MAX5084/MAX5085

65V, 200mA, Low-Quiescent-Current

Linear Regulators in TDFN

_______________________________________________________________________________________ 9

MAX5084 fig04

(V)

OUT

(mA)

5545352515

100

150

200

250

300

565

OUT

= 5V

≤ +70°C

= +85°C

= +125°C

Figure 4. Calculated Maximum Output Current vs. Input Voltage

Chip Information

PROCESS: BiCMOS

Selector Guide

PART TEMP RANGE

OUTPUT

VOLTAGE (V)

MAX5084ATT+T

-40°C to +125°C

5 or adjustable

MAX5085ATT+T

-40°C to +125°C

3.3 or adjustable

P1-P3 P4-P6 P7-P9 P10-P11

MAX5084ATT+T

Mfr. #:

Buy MAX5084ATT+T

Manufacturer:

Maxim Integrated

Description:

Linear Voltage Regulators 65V 200mA Low-Q

Lifecycle:

New from this manufacturer.

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MAX5084ATT+T

MAX5084ATT+T

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