STMicroelectronics LD1085xx User Guide

3 A low drop positive voltage regulator adjustable and fixed

Features

■ Typical dropout 1.3 V (at 3 A)

■ Three terminal adjustable or fixed output

voltage 1.5 V, 1.8 V, 2.5 V, 3.3 V, 5 V, 12 V.

■ Automotive Grade product: adjustable V

only in TO-220 Full Pack package

■ Guaranteed output current up to 3 A

■ Output tolerance ± 1 % at 25°C and ± 2 % in full

temperature range

■ Internal power and thermal limit

■ Wide operating temperature range -40 °C to

125 °C

■ Package available: TO-220, TO-220FP,

2

DPAK, D

■ Pinout compatibility with standard adjustable

PAK, D2PAK/A

VREG

Description

The LD1085xx is a low drop voltage regulator
able to provide up to 3 A of output current.
Dropout is guaranteed at a maximum of 1.2 V at
the maximum output current, decreasing at lower
loads. The LD1085xx is pin to pin compatible with
the older 3-terminal adjustable regulators, but has
better performances in term of drop and output
tolerance.

A 2.85 V output version is suitable for SCSI-2
active termination. Unlike PNP regulators, where
a part of the output current is wasted as quiescent
current, the LD1085xx quiescent current flows

OUT

LD1085xx

TO-220

D2PAKDPAK

into the load, so increase efficiency. Only a 10 µF
minimum capacitor is need for stability.

The device is supplied in TO-220, TO-220FP,
DPAK, D

2

PAK and D2PAK/A. On chip trimming
allows the regulator to reach a very tight output
voltage tolerance, within ± 1 % at 25 °C.

The LD1085xx is available as Automotive Grade
in TO-220FP package only, for the option of
adjustable output voltage whose commercial part
number is shown in the Ta bl e 1 1 (order codes).
This device is qualified according to the
specification AEC-Q100 of the Automotive
market, in the temperature range -40 °C to
125 °C, and the statistical tests PAT, SYL, SBL are
performed.

TO-220FP

D2PAK/A

Table 1. Device summary

Part numbers

LD1085XX LD1085XX25

LD1085XX15 LD1085XX33

LD1085XX18 LD1085XX50

February 2008 Rev 21 1/28

www.st.com

28

Contents LD1085xx

Contents

1 Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4 Schematic application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

5 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

6 Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

7 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

8 Order codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

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LD1085xx Diagram

1 Diagram

Figure 1. Schematic diagram

3/28

Pin configuration LD1085xx

2 Pin configuration

Figure 2. Pin connections (top view)

TO-220

D2PAK

TO-220FP

D2PAK/A

DPAK

4/28

LD1085xx Maximum ratings

3 Maximum ratings

Table 2. Absolute maximum ratings

Symbol Parameter Value Unit

T

P

T

V

I

I

O

D

STG

OP

DC input voltage 30 V

Output current Internally limited mA

Power dissipation Internally limited mW

Storage temperature range -55 to +150 °C

Operating junction temperature range -40 to +125 °C

Note: Absolute maximum ratings are those values beyond which damage to the device may occur.

Functional operation under these condition is not implied

Table 3. Thermal data

2

PAK

Symbol Parameter TO-220 DPAK

R

R

thJC

thJA

Thermal resistance junction-case 3 8 3 °C/W

Thermal resistance junction-ambient 50 100 62.5 °C/W

D

D2PAK/A

Unit

5/28

Schematic application LD1085xx

4 Schematic application

Figure 3. Application circuit

R

2

VOV

REF

⋅=

⎛⎞

1

------ -+

⎝⎠

R

1

6/28

LD1085xx Electrical characteristics

5 Electrical characteristics

Table 4. Electrical characteristics of LD1085#15

(V

= 4.5 V, CI = CO =10 µF, TA = -40 to 125 °C, unless otherwise specified).

I

Symbol Parameter Test condition Min. Typ. Max. Unit

(1)

ΔV

ΔV

V

Output voltage

O

Line regulation

O

Load regulation

O

V

Dropout voltage IO =3 A 1.3 1.5 V

d

Quiescent current VI ≤ 30 V 5 10 mA

I

q

I

Short circuit current

sc

Thermal regulation T

SVR Supply voltage rejection

eN

RMS output noise voltage (%

)

of V

O

IO = 0 mA, TJ = 25°C 1.485 1.5 1.515 V

I

= 0 to 3 A, VI = 3.1 to 30 V 1.47 1.5 1.53 V

O

I

= 0 mA, VI = 3.1 to 18 V, TJ = 25°C 0.2 4 mV

O

I

= 0 mA, VI = 3.1 to 15 V 0.4 4 mV

O

I

= 0 to 3 A, TJ = 25°C 2 10 mV

O

= 0 to 3 A 4 20 mV

I

O

V

- VO = 5 V 3.2 4.5 A

I

V

- VO = 25 V 0.2 0.5 A

I

= 25°C, 30ms pulse 0.008 0.04 %/W

A

f = 120 Hz, C

= 7.5 ± 3 V

V

I

T

= 25°C, f =10 Hz to 10 kHz 0.003 %

A

= 25 µF, IO = 3 A

O

60 72 dB

S Temperature stability 0.5 %

S Long term stability T

1. See short-circuit current curve for available output current at fixed dropout.

= 125°C, 1000Hrs 0.5 %

A

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Electrical characteristics LD1085xx

Table 5. Electrical characteristics of LD1085#18

(V

= 4.8 V, CI = CO =10 µF, TA = -40 to 125 °C, unless otherwise specified).

I

Symbol Parameter Test condition Min. Typ. Max. Unit

IO = 0 mA, TJ = 25°C 1.782 1.8 1.818 V

I

= 0 to 3 A, VI = 3.4 to 30 V 1.764 1.8 1.836 V

O

I

= 0 mA, VI = 3.4 to 18 V TJ = 25°C 0.2 4 mV

O

= 0 mA, VI = 3.4 to 15 V 0.4 4 mV

I

O

ΔV

V

O

O

Output voltage

Line regulation

(1)

IO = 0 to 3 A, TJ = 25°C 2 10 mV

ΔV

SVR Supply voltage rejection

eN

Load regulation

O

V

Dropout voltage IO = 3 A 1.3 1.5 V

d

Quiescent current VI ≤ 30 V 5 10 mA

I

q

I

Short circuit current

sc

Thermal regulation T

RMS output noise voltage (% of

)

V

O

= 0 to 3 A 4 20 mV

I

O

V

- VO = 5 V 3.2 4.5 A

I

V

- VO = 25 V 0.2 0.5 A

I

= 25°C, 30 ms pulse 0.008 0.04 %/W

A

f = 120 Hz, C

= 7.5 ± 3 V

V

I

T

= 25°C, f =10 Hz to 10 kHz 0.003 %

A

= 25 µF, IO = 3 A

O

60 72 dB

S Temperature stability 0.5 %

S Long term stability T

1. See short-circuit current curve for available output current at fixed dropout.

= 125°C, 1000 Hrs 0.5 %

A

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LD1085xx Electrical characteristics

Table 6. Electrical characteristics of LD1085#25

(V

= 5.5 V, CI = CO =10 µF, TA = -40 to 125 °C, unless otherwise specified).

I

Symbol Parameter Test condition Min. Typ. Max. Unit

V

O

Output voltage

(1)

IO = 0 mA, TJ = 25°C 2.475 2.5 2.525 V

= 0 to 3 A, VI = 4.1 to 30 V 2.45 2.5 2.55 V

I

O

IO = 0 mA, VI = 4.1 to 18 V, TJ = 25°C 0.2 4 mV

ΔV

ΔV

SVR Supply voltage rejection

eN

Line regulation

O

Load regulation

O

Dropout voltage IO = 3 A 1.3 1.5 V

V

d

I

Quiescent current VI ≤ 30 V 5 10 mA

q

I

Short circuit current

sc

Thermal regulation T

RMS output noise voltage (%
of V

)

O

= 0 mA, VI = 4.1 to 18 V 0.4 4 mV

I

O

I

= 0 to 3 A, TJ = 25°C 2 10 mV

O

I

= 0 to 3 A 4 20 mV

O

V

- VO = 5 V 3.2 4.5 A

I

- VO = 25 V 0.2 0.5 A

V

I

= 25°C, 30ms pulse 0.008 0.04 %/W

A

f = 120 Hz, C
VI = 7.5 ± 3 V

= 25°C, f =10 Hz to 10 kHz 0.003 %

T

A

= 25µF, IO = 3 A

O

60 72 dB

S Temperature stability 0.5 %

S Long term stability T

1. See short-circuit current curve for available output current at fixed dropout.

= 125°C, 1000 Hrs 0.5 %

A

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