LD2985
Very low drop and low noise voltage regulator with inhibit function
SOT23-5L
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 µVrms
• Small package SOT23-5L
• Temperature range: - 40 °C to 125 °C
Datasheet
-
production data
Description
The LD2985 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, C
BYP
= 10 nF, connected between bypass pin and GND reduces the noise to 30 µVrms. Typical application are in cellular phone, palmtop laptop computer, personal digital assistant (PDA), personal stereo, camcorder and camera.
Table 1. Device summary
Order codes Output voltages
LD2985BM18R
LD2985BM25R
LD2985BM28R
LD2985BM30R
LD2985BM31R
LD2985BM33R
LD2985BM50R
1.8 V
2.5 V
2.8 V
3.0 V
3.1 V
3.3 V
5.0 V
August 2021
This is information on a product in full production.
DocID8189 Rev 16 1/18 www.st.com
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Contents
Contents
LD2985
Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Application notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.1
External capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
6.2
Input capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
6.3
Output capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
6.4
Important . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
6.5
Inhibit input operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
6.6
Reverse current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Packing information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2/18 DocID8189 Rev 16
LD2985
1 Diagram
Figure 1. Schematic diagram
Diagram
DocID8189 Rev 16 3/18
Pin configuration LD2985
Figure 2. Pin connections (top view)
5 4
Pin n°
1
2
3
4
5
1 2 3
SC12360
Symbol
IN
GND
INHIBIT
Bypass
OUT
Table 2. Pin description
Name and function
Input port
Ground pin
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 0.18 V
Bypass pin: capacitor to be connected to GND in order to improve the thermal noise performance
Output port
Symbol
R thJC
R thJA
Table 3. Thermal data
Parameter
Thermal resistance junction-case
Thermal resistance junction-ambient
Value
81
255
Unit
°C/W
°C/W
4/18 DocID8189 Rev 16
LD2985 Maximum ratings
Note:
Symbol
V
I
V
INH
I
O
P
D
T
STG
T
OP
Table 4. Absolute maximum ratings
Parameter
DC input voltage
INHIBIT input voltage
Output current
Power dissipation
Storage temperature range
Operating junction temperature range
Value
-0.3 to 16
-0.3 to 16
Internally limited
Internally limited
-65 to 150
-40 to 125
Unit
V
V
°C
°C
Absolute maximum ratings are those values beyond which damage to the device may occur.
Functional operation under these condition is not implied.
DocID8189 Rev 16 5/18
Electrical characteristics LD2985
T
J
= 25 °C, V
I
= V
O
+ 1 V, I
O
= 50 mA, V
INH
= 2 V, C
I
= C
O
= 1 µF, unless otherwise specified.
Symbol
V
OP
V
O
V
O
V
O
V
O
V
O
V
O
V
O
I
SC
Parameter
Operating input voltage
Table 5. Electrical characteristics
Test conditions
Output voltage
Output voltage
Output voltage
Output voltage
Output voltage
Output voltage
Load regulation
Output voltage
Short-circuit current
Δ
V
O
/
Δ
V
I
Line regulation
V
I
= 2.8 V
I
O
= 1 to 150 mA
I
O
= 1 to 150 mA, T
J
= -40 to 125 °C
V
I
= 3.5 V
I
O
= 1 to 150 mA
I
O
= 1 to 150 mA, T
J
= -40 to 125 °C
V
I
= 3.8 V
I
O
= 1 to 150 mA
I
O
= 1 to 150 mA, T
J
= -40 to 125 °C
V
I
= 4.0 V
I
O
= 1 to 150 mA
I
O
= 1 to 150 mA, T
J
= -40 to 125 °C
V
I
= 4.1 V
I
O
= 1 to 150 mA
I
O
= 1 to 150 mA, T
J
= -40 to 125 °C
V
I
= 4.3 V
I
O
= 1 to 150 mA
I
O
= 1 to 150 mA, T
J
= -40 to 125 °C
I
O
= 1 to 150 mA, T
J
= -40 to 125 °C
V
I
= 6.0 V
I
O
= 1 to 150 mA
I
O
= 1 to 150 mA, T
J
= -40 to 125 °C
R
L
= 0
V
I
= V
O
+ 1 V to 16 V, I
O
= 1 mA
V
I
= V
O
+ 1 V to 16 V, I
O
= 1 mA,
T
J
= -40 to 125 °C
Min.
2.4
2.73
2.716
2.688
2.925
2.91
2.5
1.755
1.746
1.728
2.437
2.425
2.88
3.023
3.007
2.976
3.218
3.201
3.168
4.875
4.85
4.8
Typ.
Max.
Unit
V
1.8
2.5
2.8
3.0
3.1
3.3
3.432
20
5.125
5
5.15
5.2
400
0.003
0.014
3.12
3.177
3.193
3.224
3.382
3.399
2.6
2.87
2.884
2.912
3.075
3.09
16
1.845
1.854
1.872
2.562
2.575
V
V
V
V
V
V mV
V mA
%/V
I
0.032
6/18 DocID8189 Rev 16
LD2985 Electrical characteristics
Symbol
V
DROP
I
Q
SVR
V
IL
V
IH
I
INH e
N
Parameter
Table 5. Electrical characteristics (continued)
Test conditions Min.
Dropout voltage
Quiescent current
ON MODE
I
O
= 0
I
O
= 0, T
J
= -40 to 125 °C
I
O
= 1 mA
I
O
= 1 mA, T
J
= -40 to 125 °C
I
O
= 10 mA
I
O
= 10 mA, T
J
= -40 to 125 °C
I
O
= 50 mA
I
O
= 50 mA, T
J
= -40 to 125 °C
I
O
= 150 mA
I
O
= 150 mA, T
J
= -40 to 125 °C
I
O
= 0
I
O
= 0, T
J
= -40 to 125 °C
I
O
= 1 mA
I
O
= 1 mA, T
J
= -40 to 125 °C
I
O
= 10 mA
I
O
= 10 mA, T
J
= -40 to 125 °C
I
O
= 50 mA
I
O
= 50 mA, T
J
= -40 to 125 °C
I
O
= 150 mA
I
O
= 150 mA, T
J
= -40 to 125 °C
V
INH
<0.18 V
OFF MODE
V
INH
<0.18 V, T
J
= -40 to 125 °C
Supply voltage rejection C
BYP
= 0.01 µF, C
O
= 10 µF, f = 1 kHz
Inhibit input logic low
Inhibit input logic high
Inhibit input current
Output noise voltage
T
J
= -40 to 125 °C
T
J
= -40 to 125 °C
V
INH
= 0 V, T
J
= -40 to 125 °C
V
INH
= 5 V, T
J
= -40 to 125 °C
B = 300 Hz to 50 kHz, C
BYP
= 0.01 µF,
C
O
= 10 µF
2
Typ.
Max.
Unit
1
7
40
120
280
80
100
200 300
400
900 600
1200
2000 3000
4000
0
2
45
0.15
350
575
100
150
150
200
90
150
225
10
15
3
5
60 mV
µA dB
V
V
5
0
15
-1
µA
30 µV
DocID8189 Rev 16 7/18
Typical characteristics LD2985
T
J
= 25 °C, V
I
= V
O(NOM) otherwise specified.
+1 V, C
I
= 1 µF(X7R), C
O
= 2.2 µF(X7R), V
INH
= 2 V, unless
Figure 3. Output voltage vs. temperature
(V
O
= 2.5 V)
Figure 4. Dropout voltage vs. temperature
(V
O
= 2.5 V)
Figure 5. Dropout voltage vs. output current Figure 6. Quiescent current vs. load current
8/18 DocID8189 Rev 16
LD2985 Typical characteristics
Figure 7. Quiescent current vs. temperature Figure 8. Supply voltage rejection vs. temp.
Figure 9. Supply voltage rejection vs. output current (C
O
= 10 µF)
Figure 10. Supply voltage rejection vs. output current (C
O
= 1 µF)
Figure 11. Supply voltage rejection vs. frequency (C
O
= 10 µF)
Figure 12. Supply voltage rejection vs. frequency (C
O
= 1 µF)
DocID8189 Rev 16 9/18
Typical characteristics
Figure 13. Line transient (t r
= t f
= 500 ns)
LD2985
Figure 14. Line transient (t r
= t f
= 1 µs)
V
O
= 2.5 V, I
O
= 50 mA, no C
I
, C
O
= 4.7 µF, t r
= t f
= 500 ns
Figure 15. Load transient (C
O
= 10 µF)
V
O
= 2.5 V, I
O
= 50 mA, no C
I
, C
O
= 4.7 µF, t r
= t f
= 1 µs
Figure 16. Load transient (C
O
= 4.7 µF)
V
O
= 2.5 V, I
O
= 0 to 50 mA, no C
I
, C
O
= 10 µF, t r
= t f
= 500 ns V
O
= 2.5 V, I
O
= 0 to 50 mA, no C
I
, C
O
= 4.7 µF, t r
= t f
= 500 ns
10/18 DocID8189 Rev 16
LD2985 Application notes
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.
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.
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 V
O
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.
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 V
I
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 V
IH
V
IL
. Any slew rate can be used to drive the inhibit.
DocID8189 Rev 16 11/18
Application notes LD2985
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 V
REV
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. R
1
and R
2
resistors are implanted type; typical values are, respectively, 42.6 k
Ω
and 51.150 k
Ω
.
Figure 17. Reverse current test circuit
12/18 DocID8189 Rev 16
LD2985 Package information
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.
Figure 18. SOT23-5L package outline
BN
DocID8189 Rev 16 13/18
Package information LD2985
Dim.
b c
D
A
A1
A2
E e
H
L
θ
Table 6. SOT23-5L mechanical data mm
Typ.
Min.
0.90
0
0.90
0.30
0.09
0.30
0
2.95
1.60
0.95
2.80
Max.
1.45
0.15
1.30
0.50
0.20
0.60
8
Figure 19. SOT23-5L package outlineSOT23-5L recommended footprint (dimensions in mm)
BN
14/18 DocID8189 Rev 16
LD2985
Figure 20. Tape and reel SOT23-5L outline
Packing information
Figure 21. SOT23-5L reel oriented
8VHU'LUHFWLRQRI)HHG
DocID8189 Rev 16 15/18
Packing information
N
T
Ao
A
C
D
Bo
Ko
Po
P
Dim.
Table 7. Tape and reel SOT23-5L mechanical data mm
Min.
Typ.
13.0
Max.
180
13.2
12.8
20.2
60
3.13
3.07
1.27
3.9
3.9
3.23
3.17
1.37
4.0
4.0
14.4
3.33
3.27
1.47
4.1
4.1
LD2985
16/18 DocID8189 Rev 16
LD2985 Revision history
Date
22-Aug-2005
02-Sep-2005
25-Jul-2006
13-Feb-2008
04-Mar-2008
10-Jul-2008
27-Aug-2008
27-Jan-2009
09-Feb-2012
12-Nov-2013
08-Feb-2019
19-Apr-2021
30-Aug-2021
Revision
Table 8. Document revision history
Changes
4
5
6
7
8
9
10
11
12
13
14
15
16
Add new value V
O
==> 2.7 V on tables 5 and 6.
Mistake V
O
min. ==> 2.7 V on table 5.
Order codes updated.
Added: Table 1 on page 1.
Modified: Table 5 on page 6.
Modified: Table 1 on page 1 and Table 5 on page 6.
Modified: Features on page 1.
Modified: Features on page 1.
Modified: pin inhibit Figure 1 on page 3.
Removed: order codes and electrical characteristics table for type A.
RPN LD2985Bxx changed to LD2985.
Updated the Title and the Description in cover page.
Modified Table 1: Device summary, the title of the Figure 3: Output voltage vs. temperature (VO = 2.5 V) and Section 7: Package mechanical data
Added Section 8: Packaging mechanical data
Minor text changes
Updated: V
I
, V
INH
value in Table 4: Absolute maximum ratings and
Table 5: Electrical characteristics
Added: Figure 21: SOT23-5L reel oriented
Updated Table 5: Electrical characteristics
.
DocID8189 Rev 16 17/18
LD2985
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18/18 DocID8189 Rev 16
