LD2985BM25R - STMicroelectronics - Datasheet.Directory

February 2012 Doc ID 8189 Rev 12 1/18

LD2985Bxx

Very low drop and low noise voltage regulator low ESR

capacitors compatible, with inhibit function

Features

■Very low dropout voltage (280 mV at 150 mA

and 7 mV at 1 mA load)

■Very low quiescent current (2 mA typ. at 150

mA load and 80 µA at no load)

■Output current up to 150 mA

■Logic controlled electronic shutdown

■Output voltage of 1.8, 2.5, 2.8, 3, 3.1, 3.3, 5 V

■Internal current and thermal limit

■Low output noise voltage 30 mVrms

■Smallest package SOT23-5L

■Temperature range: - 40°C to 125 °C

Description

The LD2985Bxx is a 150 mA fixed output voltage

regulator. The ultra low drop voltage and the low

quiescent current make them particularly suitable

for low noise, low power applications, and in

battery powered systems. In sleep mode

quiescent current is less than 1 µA when INHIBIT

pin is pulled low. Shutdown logic control function

is available on pin 3 (TTL compatible). This

means that when the device is used as local

regulator, it is possible to put a part of the board in

standby, decreasing the total power consumption.

An external capacitor, CBYP = 10 nF, connected

between bypass pin and GND reduce the noise

to 30 µVrms. Typical application are in cellular

phone, palmtop laptop computer, personal digital

assistant (PDA), personal stereo, camcorder and

camera.

SOT23-5L

Table 1. Device summary

Part numbers Order codes Output voltages

LD2985BXX18 LD2985BM18R 1.8 V

LD2985BXX25 LD2985BM25R 2.5 V

LD2985BXX28 LD2985BM28R 2.8 V

LD2985BXX30 LD2985BM30R 3.0 V

LD2985BXX31 LD2985BM31R 3.1 V

LD2985BXX33 LD2985BM33R 3.3 V

LD2985BXX50 LD2985BM50R 5.0 V

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Contents LD2985Bxx

2/18 Doc ID 8189 Rev 12

Contents

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

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

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

4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

5 Typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

6 Application notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

6.1 External capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

6.2 Input capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

6.3 Output capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

6.4 Important . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

6.5 Inhibit input operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

6.6 Reverse current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

7 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

8 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

LD2985Bxx Diagram

Doc ID 8189 Rev 12 3/18

1 Diagram

Figure 1. Schematic diagram

Pin configuration LD2985Bxx

4/18 Doc ID 8189 Rev 12

2 Pin configuration

Figure 2. Pin connections (top view)

Table 2. Pin description

Pin n° Symbol Name and function

1 IN Input port

2 GND Ground pin

3 INHIBIT

Control switch ON/OFF. Inhibit is not internally pulled-up; it cannot be left

floating. Disable the device when connected to GND or to a positive

voltage less than 0.18V

4Bypass

Bypass pin: capacitor to be connected to GND in order to improve the

thermal noise performances

5 OUT Output port

Table 3. Thermal data

Symbol Parameter Value Unit

RthJC Thermal resistance junction-case 81 °C/W

RthJA Thermal resistance junction-ambient 255 °C/W

SC12360

123

LD2985Bxx Maximum ratings

Doc ID 8189 Rev 12 5/18

3 Maximum ratings

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

Functional operation under these condition is not implied.

Table 4. Absolute maximum ratings

Symbol Parameter Value Unit

VIDC input voltage 16 V

VINH INHIBIT input voltage 16 V

IOOutput current Internally limited

PDPower dissipation Internally limited

TSTG Storage temperature range -65 to 150 °C

TOP Operating junction temperature range -40 to 125 °C

Electrical characteristics LD2985Bxx

6/18 Doc ID 8189 Rev 12

4 Electrical characteristics

TJ = 25 °C, VI = VO + 1 V, IO = 50 mA, VINH= 2 V, CI = CO = 1 µF, unless otherwise specified.

Table 5. Electrical characteristics

Symbol Parameter Test conditions Min. Typ. Max. Unit

VOP Operating input voltage 2.5 16 V

VOOutput voltage

VI = 2.5V 1.463 1.5 1.537

VIO = 1 to 150mA 1.455 1.545

IO = 1 to 150mA, TJ= -40 to 125°C 1.440 1.560

VOOutput voltage

VI = 2.8V 1.755 1.8 1.845

VIO = 1 to 150mA 1.746 1.854

IO = 1 to 150mA, TJ= -40 to 125°C 1.728 1.872

VOOutput voltage

VI = 3.5V 2.437 2.5 2.562

VIO = 1 to 150mA 2.425 2.575

IO = 1 to 150mA, TJ= -40 to 125°C 2.4 2.6

VOOutput voltage

VI = 3.5V 2.633 2.7 2.767

VIO = 1 to 150mA 2.619 2.781

IO = 1 to 150mA, TJ= -40 to 125°C 2.592 2.808

VOOutput voltage

VI = 3.8V 2.73 2.8 2.87

VIO = 1 to 150mA 2.716 2.884

IO = 1 to 150mA, TJ= -40 to 125°C 2.688 2.912

VOOutput voltage

VI = 3.85V 2.779 2.85 2.921

VIO = 1 to 150mA 2.764 2.935

IO = 1 to 150mA, TJ= -40 to 125°C 2.736 2.964

VOOutput voltage

VI = 4.0V 2.925 3.0 3.075

VIO = 1 to 150mA 2.91 3.09

IO = 1 to 150mA, TJ= -40 to 125°C 2.88 3.12

VOOutput voltage

VI = 4.1V 3.023 3.1 3.177

VIO = 1 to 150mA 3.007 3.193

IO = 1 to 150mA, TJ= -40 to 125°C 2.976 3.224

VOOutput voltage

VI = 4.2V 3.120 3.2 3.28

VIO = 1 to 150mA 3.104 3.296

IO = 1 to 150mA, TJ= -40 to 125°C 3.072 3.328

VOOutput voltage

VI = 4.3V 3.218 3.3 3.382

VIO = 1 to 150mA 3.201 3.399

IO = 1 to 150mA, TJ= -40 to 125°C 3.168 3.432

VOOutput voltage

VI = 4.5V 3.413 3.5 3.587

VIO = 1 to 150mA 3.395 3.605

IO = 1 to 150mA, TJ= -40 to 125°C 3.360 3.640

LD2985Bxx Electrical characteristics

Doc ID 8189 Rev 12 7/18

VOOutput voltage

VI = 4.6V 3.51 3.6 3.69

VIO = 1 to 150mA 3.492 3.708

IO = 1 to 150mA, TJ= -40 to 125°C 3.456 3.744

VOOutput voltage

VI = 4.8V 3.705 3.8 3.895

VIO = 1 to 150mA 3.686 3.914

IO = 1 to 150mA, TJ= -40 to 125°C 3.648 3.952

VOOutput voltage

VI = 5.0V 3.900 4 4.100

VIO = 1 to 150mA 3.88 4.12

IO = 1 to 150mA, TJ= -40 to 125°C 3.84 4.16

VOOutput voltage

VI = 5.7V 4.583 4.7 4.817

VIO = 1 to 150mA 4.559 4.841

IO = 1 to 150mA, TJ= -40 to 125°C 4.512 4.888

VOOutput voltage

VI = 6.0V 4.875 5 5.125

VIO = 1 to 150mA 4.85 5.15

IO = 1 to 150 mA, TJ= -40 to 125°C 4.8 5.2

ISC Short circuit current RL = 0 400 mA

ΔVO/ΔVILine regulation

VI = VO + 1V to 16V, IO = 1 mA 0.003 0.014

%/VI

VI = VO + 1V to 16V, IO = 1 mA,

TJ= -40 to 125°C 0.032

VDROP Dropout voltage

IO = 0 1 3

IO = 0, TJ= -40 to 125°C 5

IO = 1mA 7 10

IO = 1mA, TJ= -40 to 125°C 15

IO = 10mA 40 60

IO = 10mA, TJ= -40 to 125°C 90

IO = 50mA 120 150

IO = 50mA, TJ= -40 to 125°C 225

IO = 150mA 280 350

IO = 150mA, TJ= -40 to 125°C 575

Table 5. Electrical characteristics (continued)

Symbol Parameter Test conditions Min. Typ. Max. Unit

Electrical characteristics LD2985Bxx

8/18 Doc ID 8189 Rev 12

Quiescent current

ON MODE

IO = 0 80 100

µA

IO = 0, TJ= -40 to 125°C 150

IO = 1mA 100 150

IO = 1mA, TJ= -40 to 125°C 200

IO = 10mA 200 300

IO = 10mA, TJ= -40 to 125°C 400

IO = 50mA 600 900

IO = 50mA, TJ= -40 to 125°C 1200

IO = 150mA 2000 3000

IO = 150mA, TJ= -40 to 125°C 4000

OFF MODE VINH<0.18V 0

VINH<0.18V, TJ= -40 to 125°C 2

SVR Supply voltage rejection CBYP = 0.01µF, CO = 10µF, f = 1kHz 45 dB

VIL Inhibit input logic low TJ= -40 to 125°C 0.15 V

VIH Inhibit input logic high TJ= -40 to 125°C 2 V

IINH Inhibit input current VINH = 0V, TJ= -40 to 125°C 5 15 µA

VINH = 5V, TJ= -40 to 125°C 0 -1

eNOutput noise voltage B = 300 Hz to 50 kHz, CBYP = 0.01µF,

CO = 10µF 30 µV

Table 5. Electrical characteristics (continued)

Symbol Parameter Test conditions Min. Typ. Max. Unit

LD2985Bxx Typical characteristics

Doc ID 8189 Rev 12 9/18

5 Typical characteristics

TJ = 25 °C, VI = VO(NOM) +1 V, CI = 1 µF(X7R), CO = 2.2 µF(X7R), VINH = 2 V, unless

otherwise specified.

Figure 3. Output voltage vs. temperature

(VI = 3.5 V)

Figure 4. Dropout voltage vs. temperature

(VO = 2.5 V)

Figure 5. Dropout voltage vs. output current Figure 6. Quiescent current vs. load current

Figure 7. Quiescent current vs. temperature Figure 8. Supply voltage rejection vs. temp.

Typical characteristics LD2985Bxx

10/18 Doc ID 8189 Rev 12

Figure 9. Supply voltage rejection vs. output

current (CO = 10 µF)

Figure 10. Supply voltage rejection vs. output

current (CO = 1 µF)

Figure 11. Supply voltage rejection vs.

frequency (CO = 10 µF)

Figure 12. Supply voltage rejection vs.

frequency (CO = 1 µF)

Figure 13. Line transient (tr = tf = 500 ns) Figure 14. Line transient (tr = tf = 1 µs)

VO = 2.5V, IO = 50mA, no CI, CO = 4.7µF, tr=tf=500ns

VO = 2.5V, IO = 50mA, no CI, CO = 4.7µF, tr=tf=1µs

LD2985Bxx Typical characteristics

Doc ID 8189 Rev 12 11/18

Figure 15. Load transient (CO = 10 µF) Figure 16. Load transient (CO = 4.7 µF)

VO = 2.5V, IO = 0 to 50mA, no CI, CO = 10µF, tr=tf=500ns

VO = 2.5V, IO = 0 to 50mA, no CI, CO = 4.7µF, tr=tf=500ns

Application notes LD2985Bxx

12/18 Doc ID 8189 Rev 12

6 Application notes

6.1 External capacitors

Like any low-dropout regulator, the LD2985 requires external capacitors for regulator

stability. This capacitor must be selected to meet the requirements of minimum capacitance

and equivalent series resistance. We suggest to solder input and output capacitors as close

as possible to the relative pins.

6.2 Input capacitor

An input capacitor whose value is 1 µF is required with the LD2985 (amount of capacitance

can be increased without limit). This capacitor must be located a distance of not more than

0.5" from the input pin of the device and returned to a clean analog ground. Any good quality

ceramic, tantalum or film capacitors can be used for this capacitor.

6.3 Output capacitor

The LD2985 is designed specifically to work with ceramic output capacitors. It may also be

possible to use Tantalum capacitors, but these are not as attractive for reasons of size and

cost. By the way, the output capacitor must meet both the requirement for minimum amount

of capacitance and ESR (equivalent series resistance) value. Due to the different loop gain,

the stability improves for higher output versions and so the suggested minimum output

capacitor value, if low ESR ceramic type is used, is 1 µF for output voltages equal or major

than 3.8 V, 2.2 µF for VO going from 1.8 to 3.3 V, and 3.3 µF for the other versions. However,

if an output capacitor lower than the suggested one is used, it's possible to make stable the

regulator adding a resistor in series to the capacitor.

6.4 Important

The output capacitor must maintain its ESR in the stable region over the full operating

temperature to assure stability. Also, capacitor tolerance and variation with temperature

must be considered to assure the minimum amount of capacitance is provided at all times.

This capacitor should be located not more than 0.5" from the output pin of the device and

returned to a clean analog ground.

6.5 Inhibit input operation

The inhibit pin can be used to turn OFF the regulator when pulled low, so drastically

reducing the current consumption down to less than 1 µA. When the inhibit feature is not

used, this pin must be tied to VI to keep the regulator output ON at all times. To assure

proper operation, the signal source used to drive the inhibit pin must be able to swing above

and below the specified thresholds listed in the electrical characteristics section under VIH

VIL. Any slew rate can be used to drive the inhibit.

LD2985Bxx Application notes

Doc ID 8189 Rev 12 13/18

6.6 Reverse current

The power transistor used in the LD2985 has not an inherent diode connected between the

regulator input and output. If the output is forced above the input, no current will flow from

the output to the input across the series pass transistor. When a VREV voltage is applied on

the output, the reverse current measured flows to the GND across the two feedback

resistors. This current typical value is 160 µA. R1 and R2 resistors are implanted type;

typical values are, respectively, 42.6 kΩ and 51.150 kΩ.

Figure 17. Reverse current test circuit

Package mechanical data LD2985Bxx

14/18 Doc ID 8189 Rev 12

7 Package mechanical data

In order to meet environmental requirements, ST offers these devices in different grades of

ECOPACK® packages, depending on their level of environmental compliance. ECOPACK®

specifications, grade definitions and product status are available at: www.st.com.

ECOPACK® is an ST trademark.

LD2985Bxx Package mechanical data

Doc ID 8189 Rev 12 15/18

Dim.

mm. mils.

Min. Typ. Max. Min. Typ. Max.

A0.90 1.45 35.4 57.1

A1 0.00 0.10 0.0 3.9

A2 0.90 1.3035.4 51.2

b0.35 0.50 13.7 19.7

C0.090.20 3.5 7.8

D2.803.00 110.2 118.1

E 1.50 1.75 59.0 68.8

e0.9537.4

H 2.60 3.00 102.3118.1

L 0.10 0.60 3.923.6

SOT23-5L mechanical data

7049676D

Package mechanical data LD2985Bxx

16/18 Doc ID 8189 Rev 12

Dim.

mm. inch.

Min. Typ. Max. Min. Typ. Max.

A180 7.086

C 12.813.0 13.2 0.504 0.512 0.519

D 20.2 0.795

N60 2.362

T 14.4 0.567

Ao 3.133.233.33 0.1230.127 0.131

Bo 3.07 3.17 3.27 0.120 0.124 0.128

Ko 1.27 1.37 1.47 0.050 0.054 0.0.58

Po 3.94.0 4.1 0.1530.157 0.161

P3.94.0 4.1 0.1530.157 0.161

Tape & reel SOT23-xL mechanical data

LD2985Bxx Revision history

Doc ID 8189 Rev 12 17/18

8 Revision history

Table 6. Document revision history

Date Revision Changes

22-Aug-2005 4 Add new value VO ==> 2.7 V on tables 5 and 6.

02-Sep-2005 5 Mistake VO min. ==> 2.7 V on table 5.

25-Jul-2006 6 Order codes updated.

13-Feb-2008 7 Added:

Table 1 on page 1

04-Mar-2008 8 Modified:

Table 5 on page 6

10-Jul-2008 9 Modified:

Table 1 on page 1

and

Table 5 on page 6

27-Aug-2008 10 Modified

: Features on page 1

27-Jan-2009 11 Modified

: Features on page 1

09-Feb-2012 12 Modified: pin inhibit

Figure 1 on page 3

Removed: order codes and electrical characteristics table for type A.

LD2985Bxx

18/18 Doc ID 8189 Rev 12

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