LP2985-30DBVT [TI]
150-mA LOW-NOISE LOW-DROPOUT REGULATOR WITH SHUTDOWN; 具有关断功能的150 mA的低噪声低压降稳压器
| 型号： | LP2985-30DBVT |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | 150-mA LOW-NOISE LOW-DROPOUT REGULATOR WITH SHUTDOWN |
| 文件： | 总24页 (文件大小：782K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LP2985
150-mA LOW-NOISE LOW-DROPOUT REGULATOR
WITH SHUTDOWN
www.ti.com
SLVS522F–JULY 2004–REVISED AUGUST 2005
FEATURES
PORTABLE APPLICATIONS
•
•
•
•
•
•
Cellular Phones
•
Output Tolerance of
Palmtop and Laptop Computers
Personal Digital Assistants (PDAs)
Digital Cameras and Camcorders
CD Players
– 1% (A Grade)
– 1.5% (Standard Grade)
Ultra-Low Dropout, Typically
– 280 mV at Full Load of 150 mA
– 7 mV at 1 mA
•
MP3 Players
•
•
•
•
Wide VIN Range…16 V Max
Low IQ . . . 850 µA at Full Load at 150 mA
Shutdown Current . . . 0.01 µA Typ
DBV (SOT-23) PACKAGE
(TOP VIEW)
1
2
3
5
4
V
GND
V
OUT
IN
Low Noise . . . 30 µVRMS With 10-nF Bypass
Capacitor
ON/OFF
BYPASS
•
Stable With Low-ESR Capacitors, Including
Ceramic
•
•
Overcurrent and Thermal Protection
High Peak-Current Capability
DESCRIPTION/ORDERING INFORMATION
The LP2985 family of fixed-output, low-dropout regulators offers exceptional, cost-effective performance for both
portable and nonportable applications. Available in voltages of 1.8 V, 2.8 V, 2.9 V, 3 V, 3.3 V and 5 V, the family
has an output tolerance of 1% for the A version (1.5% for the non-A version) and is capable of delivering 150-mA
continuous load current. Standard regulator features, such as overcurrent and overtemperature protection, are
included.
The LP2985 has a host of features that makes the regulator an ideal candidate for a variety of portable
applications:
•
•
•
•
•
•
Low dropout: A PNP pass element allows a typical dropout of 280 mV at 150-mA load current and 7 mV at
1-mA load.
Low quiescent current: The use of a vertical PNP process allows for quiescent currents that are considerably
lower than those associated with traditional lateral PNP regulators.
Shutdown: A shutdown feature is available, allowing the regulator to consume only 0.01 µA when the
ON/OFF pin is pulled low.
Low-ESR-capacitor friendly: The regulator is stable with low-ESR capacitors, allowing the use of small,
inexpensive, ceramic capacitors in cost-sensitive applications.
Low noise: A BYPASS pin allows for low-noise operation, with a typical output noise of 30 µVRMS, with the
use of a 10-nF bypass capacitor.
Small packaging: For the most space-constrained needs, the regulator is available in the SOT-23 package.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2004–2005, Texas Instruments Incorporated
LP2985
150-mA LOW-NOISE LOW-DROPOUT REGULATOR
WITH SHUTDOWN
www.ti.com
SLVS522F–JULY 2004–REVISED AUGUST 2005
ORDERING INFORMATION
PART
GRADE
VOUT
(NOM)
ORDERABLE
PART NUMBER
TOP-SIDE
TJ
PACKAGE(1)
MARKING(2)
Reel of 3000
Reel of 250
Reel of 3000
Reel of 250
Reel of 3000
Reel of 250
Reel of 3000
Reel of 250
Reel of 3000
Reel of 250
Reel of 3000
LP2985A-18DBVR
LP2985A-18DBVT
LP2985A-28DBVR
LP2985A-28DBVT
LP2985A-29DBVR
LP2985A-29DBVT
LP2985A-30DBVR
LP2985A-30DBVT
LP2985A-33DBVR
LP2985A-33DBVT
LP2985A-50DBVR
LP2985A-50DBVT
LP2985-18DBVR
LP2985-18DBVT
LP2985-28DBVR
LP2985-28DBVT
LP2985-29DBVR
LP2985-29DBVT
LP2985-30DBVR
LP2985-30DBVT
LP2985-33DBVR
LP2985-33DBVT
LP2985-50DBVR
LP2985-50DBVT
1.8 V
2.8 V
2.9 V
3.0 V
3.3 V
5.0 V
1.8 V
2.8 V
2.9 V
3.0 V
3.3 V
5.0 V
LPT3
LPJ3
PREVIEW
PREVIEW
LPK3
A grade:
1% tolerance
PREVIEW
LPH3
Reel of 250
SOT-23-5 – DBV
–40°C to 125°C
Reel of 3000
Reel of 250
Reel of 3000
Reel of 250
Reel of 3000
Reel of 250
Reel of 3000
Reel of 250
Reel of 3000
Reel of 250
Reel of 3000
Reel of 250
LPG3
PREVIEW
PREVIEW
LPF3
Standard grade:
1.5% tolerance
PREVIEW
(1) Package drawings, standard packing quantities, thermal data, symbolization, and PCB design guidelines are available at
www.ti.com/sc/package.
(2) The actual top-side marking has one additional character that designates the assembly/test site.
2
LP2985
150-mA LOW-NOISE LOW-DROPOUT REGULATOR
WITH SHUTDOWN
www.ti.com
SLVS522F–JULY 2004–REVISED AUGUST 2005
FUNCTIONAL BLOCK DIAGRAM
V
IN
ON/OFF
1.23 V
V
REF
−
+
BYPASS
V
OUT
Overcurrent/
Overtemperature
Protection
BASIC APPLICATION CIRCUIT
LP2985
V
OUT
V
1
2
5
IN
2.2 µF
(see Note A)
1 µF
(see Note A)
GND
ON/OFF
(see Note B)
3
4
BYPASS
10 nF
(see Note C)
A. Minimum COUT value for stability (can be increased without limit for improved stability and transient response)
B. ON/OFF must be actively terminated. Connect to VIN if shutdown feature is not used.
C. Optional BYPASS capacitor for low-noise operation
3
LP2985
150-mA LOW-NOISE LOW-DROPOUT REGULATOR
WITH SHUTDOWN
www.ti.com
SLVS522F–JULY 2004–REVISED AUGUST 2005
Absolute Maximum Ratings(1)
over virtual junction temperature range (unless otherwise noted)
MIN
–0.3
–0.3
–0.3
–0.3
MAX
16
UNIT
VIN
Continuous input voltage range
ON/OFF input voltage range
Output voltage range(2)
V
VON/OFF
16
9
V
V
V
VIN – VOUT Input/output voltage differential range(3)
16
Internally limited
(short-circuit protected)
IO
Output current(4)
θJA
TJ
Package thermal impedance(4)(5)
Operating virtual junction temperature
Storage temperature range
206
150
°C/W
°C
Tstg
–65
150
°C
(1) Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating
conditions" is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
(2) If load is returned to a negative power supply in a dual-supply system, the output must be diode clamped to GND.
(3) The PNP pass transistor has a parasitic diode connected between the input and output. This diode normally is reverse biased
(VIN > VOUT), but will be forward biased if the output voltage exceeds the input voltage by a diode drop (see Application Information for
more details).
(4) Maximum power dissipation is a function of TJ(max), θJA, and TA. The maximum allowable power dissipation at any allowable ambient
temperature is PD = (TJ(max) – TA)/θJA. Operating at the absolute maximum TJ of 150°C can affect reliability.
(5) The package thermal impedance is calculated in accordance with JESD 51-7.
Recommended Operating Conditions
MIN
2.2(1)
0
MAX
16
UNIT
V
VIN
Supply input voltage
ON/OFF input voltage
Output current
VON/OFF
IOUT
TJ
VIN
V
150
125
mA
°C
Virtual junction temperature
–40
(1) Recommended minimum VIN is the greater of 2.5 V or VOUT(max) + rated dropout voltage (max) for operating IL.
4
LP2985
150-mA LOW-NOISE LOW-DROPOUT REGULATOR
WITH SHUTDOWN
www.ti.com
SLVS522F–JULY 2004–REVISED AUGUST 2005
Electrical Characteristics
at specified virtual junction temperature range, VIN = VOUT(NOM) + 1 V, VON/OFF = 2 V, CIN = 1 µF, IL = 1 mA, COUT = 4.7 µF
(unless otherwise noted)
LP2985A-xx
MIN TYP
LP2985-xx
MIN TYP
PARAMETER
TEST CONDITIONS
IL = 1 mA
TJ
UNIT
MAX
1
MAX
1.5
25°C
25°C
–1
–1.5
–2.5
–2.5
–3.5
–1.5
–2.5
–3.5
–3
1.5
2.5
2.5
3.5
2.5
Output
1 mA ≤ IL ≤ 50 mA
1 mA ≤ IL ≤ 150 mA
VIN = [VOUT(NOM) + 1 V] to 16 V
IL = 0
∆VOUT
voltage
tolerance
–40°C to 125°C
25°C
3.5 %VNOM
3
4
–40°C to 125°C
25°C
–4
0.007 0.014
0.032
0.007 0.014
0.032
Line
regulation
%/V
–40°C to 125°C
25°C
1
3
5
1
3
5
–40°C to 125°C
25°C
7
10
7
10
IL = 1 mA
–40°C to 125°C
25°C
15
15
40
60
40
60
Dropout
VIN – VOUT
IL = 10 mA
mV
voltage(1)
–40°C to 125°C
25°C
90
90
120
280
65
150
225
350
575
95
120
280
65
150
225
350
575
95
IL = 50 mA
–40°C to 125°C
25°C
IL = 150 mA
IL = 0
–40°C to 125°C
25°C
–40°C to 125°C
25°C
125
110
170
220
400
600
1000
1500
2500
0.8
2
125
110
170
220
400
600
1000
1500
2500
0.8
2
75
75
IL = 1 mA
–40°C to 125°C
25°C
120
350
850
120
350
850
IL = 10 mA
–40°C to 125°C
25°C
Ground
pin
current
IGND
µA
IL = 50 mA
–40°C to 125°C
25°C
IL = 150 mA
–40°C to 125°C
25°C
VON/OFF < 0.3 V (OFF)
VON/OFF < 0.15 V (OFF)
0.01
0.05
0.01
0.05
–40°C to 105°C
–40°C to 125°C
25°C
5
5
1.4
0.55
0.01
5
1.4
0.55
0.01
5
VON/OFF = HIGH → O/P ON
VON/OFF = LOW → O/P OFF
VON/OFF = 0
ON/OFF
input
–40°C to 125°C
25°C
1.6
1.6
VON/OFF
V
voltage(2)
–40°C to 125°C
25°C
0.15
–2
0.15
–2
ON/OFF
input
–40°C to 125°C
25°C
ION/OFF
µA
current
VON/OFF = 5 V
–40°C to 125°C
15
15
Output
noise
(RMS)
BW = 300 Hz to 50 kHz,
COUT = 10 µF,
CBYPASS = 10 nF
Vn
25°C
25°C
30
45
30
45
µV
Ripple
rejection
f = 1kHz, COUT = 10 µF,
CBYPASS = 10 nF
∆VOUT/∆VIN
dB
(1) Dropout voltage is defined as the input-to-output differential at which the output voltage drops 100 mV below the value measured with a
1-V differential.
(2) The ON/OFF input must be driven properly for reliable operation (see Application Information).
5
LP2985
150-mA LOW-NOISE LOW-DROPOUT REGULATOR
WITH SHUTDOWN
www.ti.com
SLVS522F–JULY 2004–REVISED AUGUST 2005
Electrical Characteristics (continued)
at specified virtual junction temperature range, VIN = VOUT(NOM) + 1 V, VON/OFF = 2 V, CIN = 1 µF, IL = 1 mA, COUT = 4.7 µF
(unless otherwise noted)
LP2985A-xx
LP2985-xx
PARAMETER
Peak output
TEST CONDITIONS
TJ
UNIT
MIN
TYP
MAX
MIN
TYP
MAX
IOUT(PK)
V
OUT ≥ VO(NOM) – 5%
25°C
25°C
350
350
mA
mA
current
Short-circuit
current
IOUT(SC)
RL = 0 (steady state)(3)
400
400
(3) See Figure 5 in Typical Performance Characteristics.
6
LP2985
150-mA LOW-NOISE LOW-DROPOUT REGULATOR
WITH SHUTDOWN
www.ti.com
SLVS522F–JULY 2004–REVISED AUGUST 2005
TYPICAL PERFORMANCE CHARACTERISTICS
CIN = 1 µF, COUT = 4.7 µF, VIN = VOUT(NOM) +1 V, TA = 25°C, ON/OFF Pin Tied to VIN (unless otherwise specified)
OUTPUT VOLTAGE
vs
TEMPERATURE
DROPOUT VOLTAGE
vs
TEMPERATURE
0.45
0.4
3.345
3.335
3.325
150 mA
V
C
= 3.3 V
O
V = 4.3 V
I
= 10 nF
byp
V
O
= 3.3 V
C = 1 µF
i
C = 4.7 µF
0.35
0.3
o
I
O
= 1 mA
0.25
0.2
3.315
3.305
3.295
50 mA
10 mA
0.15
0.1
0.05
0
1 mA
100 125 150
−50 −25
−50
−25
0
25
50
75
0
25
50
75
100
125 150
Temperature − °C
Temperature − °C
Figure 1.
Figure 2.
SHORT-CIRCUIT CURRENT
SHORT-CIRCUIT CURRENT
vs
vs
TIME
TIME
0.5
0.5
0.45
0.4
V = 16 V
I
V = 6 V
I
V
O
= 3.3 V
V
O
= 3.3 V
0.45
0.4
C = 1 µF
i
C = 1 µF
i
C
byp
= 0.01 µF
C
byp
= 0.01 µF
0.35
0.3
0.35
0.3
0.25
0.2
0.25
0.2
0.15
0.1
0.15
0.1
0.05
0.05
0
0
−100
100
300
Time − ms
500
700
−500
0
500
Time − ms
Figure 3.
1000
1500
2000
Figure 4.
7
LP2985
150-mA LOW-NOISE LOW-DROPOUT REGULATOR
WITH SHUTDOWN
www.ti.com
SLVS522F–JULY 2004–REVISED AUGUST 2005
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
CIN = 1 µF, COUT = 4.7 µF, VIN = VOUT(NOM) +1 V, TA = 25°C, ON/OFF Pin Tied to VIN (unless otherwise specified)
SHORT-CIRCUIT CURRENT
vs
GROUND-PIN CURRENT
vs
OUTPUT VOLTAGE
LOAD CURRENT
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
320
300
280
V
C
= 3.3 V
O
V
= 3.3 V
O
= 10 nF
byp
260
240
220
200
0
0.5
1
1.5
2
2.5
3
3.5
20
40
60
80
100
120
140
160
0
Output Voltage − V
Load Current − mA
Figure 5.
Figure 6.
RIPPLE REJECTION
vs
RIPPLE REJECTION
vs
FREQUENCY
FREQUENCY
100
100
90
80
70
60
50
40
30
20
10
0
V = 3.7 V
V = 5 V
I
I
90
80
70
60
50
40
30
20
10
0
V
O
= 3.3 V
V
O
= 3.3 V
C
C
= 10 µF
C
C
= 10 µF
o
o
= 0 nF
= 0 nF
byp
byp
50 mA
1 mA
1 mA
50 mA
150 mA
150 mA
10
100
1k
10k
100k
1M
10
100
1k
10k
100k
1M
Frequency − Hz
Frequency − Hz
Figure 7.
Figure 8.
8
LP2985
150-mA LOW-NOISE LOW-DROPOUT REGULATOR
WITH SHUTDOWN
www.ti.com
SLVS522F–JULY 2004–REVISED AUGUST 2005
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
CIN = 1 µF, COUT = 4.7 µF, VIN = VOUT(NOM) +1 V, TA = 25°C, ON/OFF Pin Tied to VIN (unless otherwise specified)
RIPPLE REJECTION
vs
RIPPLE REJECTION
vs
FREQUENCY
FREQUENCY
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
V = 5 V
V = 5 V
I
I
V
O
= 3.3 V
V
O
= 3.3 V
C
C
= 4.7 µF
C
C
= 4.7 µF
o
o
= 10 nF
= 10 nF
byp
byp
1 mA
1 mA
10 mA
50 mA
150 mA
100 mA
10
100
1k
10k
100k
1M
10
100
1k
10k
100k
1M
Frequency − Hz
Frequency − Hz
Figure 9.
Figure 10.
OUTPUT IMPEDANCE
vs
OUTPUT IMPEDANCE
vs
FREQUENCY
FREQUENCY
10
10
C = 1 µF
i
C = 1 µF
i
C = 4.7 µF
C
V
= 10 µF
= 3.3 V
o
o
V
O
= 3.3 V
O
1
1 mA
1
1 mA
10 mA
10 mA
100 mA
100 mA
0.1
0.01
0.1
0.01
0.001
0.001
10
100
1k
10k
100k
1M
10
100
1k
10k
100k
1M
Frequency − Hz
Frequency − Hz
Figure 11.
Figure 12.
9
LP2985
150-mA LOW-NOISE LOW-DROPOUT REGULATOR
WITH SHUTDOWN
www.ti.com
SLVS522F–JULY 2004–REVISED AUGUST 2005
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
CIN = 1 µF, COUT = 4.7 µF, VIN = VOUT(NOM) +1 V, TA = 25°C, ON/OFF Pin Tied to VIN (unless otherwise specified)
OUTPUT NOISE DENSITY
OUTPUT NOISE DENSITY
vs
vs
FREQUENCY
FREQUENCY
10
10
I
= 1 mA
LOAD
I
= 150 mA
LOAD
1
1
C
byp
= 100 nF
C
byp
= 100 nF
C
byp
= 1 nF
C
byp
= 1 nF
0.1
0.01
0.1
0.01
C
byp
= 10 nF
C
byp
= 10 nF
100
1k
10k
100k
100
1k
10k
100k
Frequency − Hz
Frequency − Hz
Figure 13.
Figure 14.
INPUT CURRENT
vs
INPUT VOLTAGE
GROUND-PIN CURRENT
vs
TEMPERATURE
1.8
1400
1200
1000
800
600
400
200
0
V
C
= 3.3 V
V
C
= 3.3 V
O
O
= 10 nF
1.6
1.4
1.2
1
= 10 nF
byp
byp
R
= 3.3 kΩ
L
150 mA
0.8
0.6
R
= Open
1 mA
0 mA
L
50 mA
10 mA
0.4
0.2
0
0
1
2
3
4
5
6
−50
−25
0
25
50
75
100 125
150
Input Voltage − V
Temperature − °C
Figure 15.
Figure 16.
10
LP2985
150-mA LOW-NOISE LOW-DROPOUT REGULATOR
WITH SHUTDOWN
www.ti.com
SLVS522F–JULY 2004–REVISED AUGUST 2005
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
CIN = 1 µF, COUT = 4.7 µF, VIN = VOUT(NOM) +1 V, TA = 25°C, ON/OFF Pin Tied to VIN (unless otherwise specified)
LOAD TRANSIENT RESPONSE
LOAD TRANSIENT RESPONSE
200
150
100
50
200
150
100
50
3.4
3.38
3.36
3.34
3.32
3.3
3.4
3.38
3.36
3.34
3.32
3.3
I
I
L
L
V
C
= 3.3 V
O
0
V
C
= 3.3 V
0
O
= 10 nF
byp
= 10 nF
byp
∆I = 100 mA
L
−50
∆I = 150 mA
L
−50
V
O
V
O
−100
−150
−200
−250
3.28
3.26
3.24
3.22
−100
−150
−200
−250
3.28
3.26
3.24
3.22
20 µs/div"
20 µs/div"
Figure 17.
Figure 18.
LOAD TRANSIENT RESPONSE
LINE TRANSIENT RESPONSE
3.4
3.38
3.36
3.34
3.32
3.3
3.41
200
5.5
150
100
50
3.39
3.37
3.35
3.33
3.31
3.29
3.27
5
V
I
4.5
I
L
V
= 3.3 V
= 0 nF
= 150 mA
O
V
C
= 3.3 V
= 0 nF
C
I
O
byp
4
0
byp
O
∆I = 150 mA
L
−50
3.5
V
O
−100
−150
−200
−250
3.28
3.26
V
O
3
2.5
3.24
3.22
2
20 µs/div"
20 µs/div"
Figure 20.
Figure 19.
11
LP2985
150-mA LOW-NOISE LOW-DROPOUT REGULATOR
WITH SHUTDOWN
www.ti.com
SLVS522F–JULY 2004–REVISED AUGUST 2005
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
CIN = 1 µF, COUT = 4.7 µF, VIN = VOUT(NOM) +1 V, TA = 25°C, ON/OFF Pin Tied to VIN (unless otherwise specified)
LINE TRANSIENT RESPONSE
LINE TRANSIENT RESPONSE
3.41
3.39
3.41
3.39
3.37
5.5
5
5.5
5
V
I
V
4.5
4.5
I
3.37
3.35
V
C
= 3.3 V
= 0 nF
byp
= 1 mA
V
= 3.3 V
O
O
4
4
C
I
= 10 nF
3.35
3.33
3.31
3.29
3.27
byp
I
O
= 150 mA
O
3.5
3
3.5
3.33
3
3.31
3.29
3.27
2.5
2.5
V
O
V
O
2
2
20 µs/div"
20 µs/div"
Figure 21.
Figure 22.
LINE TRANSIENT RESPONSE
TURN-ON TIME
5.5
4
3
2
1
3.41
3.39
3.37
10
8
V
O
5
V
IN
4.5
6
4
3.35
3.33
3.31
V
= 3.3 V
O
0
C
I
= 10 nF
byp
3.5
= 1 mA
O
V
C
= 3.3 V
O
4
−1
= 0
byp
I
O
= 150 mA
3
V
O
−2
−3
−4
V
ON/OFF
2
2.5
2
3.29
3.27
0
100 µs/div"
100 µs/div"
Figure 23.
Figure 24.
12
LP2985
150-mA LOW-NOISE LOW-DROPOUT REGULATOR
WITH SHUTDOWN
www.ti.com
SLVS522F–JULY 2004–REVISED AUGUST 2005
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
CIN = 1 µF, COUT = 4.7 µF, VIN = VOUT(NOM) +1 V, TA = 25°C, ON/OFF Pin Tied to VIN (unless otherwise specified)
TURN-ON TIME
TURN-ON TIME
10
8
10
4
3
4
3
V
O
V
O
8
6
4
2
0
2
2
1
1
6
0
0
V
C
= 3.3 V
= 1 nF
= 150 mA
4
O
V
C
= 3.3 V
O
−1
−2
−3
−4
−1
−2
byp
= 100 pF
byp
I
LOAD
I
= 150 mA
LOAD
V
ON/OFF
V
ON/OFF
2
−3
−4
0
2 ms/div"
200 µs/div"
Figure 25.
Figure 26.
TURN-ON TIME
4
3
2
10
Input
8
6
4
2
0
1
0
V
C
= 3.3 V
O
−1
−2
= 10 nF
byp
I
= 150 mA
LOAD
Output
−3
−4
20 ms/div"
Figure 27.
13
LP2985
150-mA LOW-NOISE LOW-DROPOUT REGULATOR
WITH SHUTDOWN
www.ti.com
SLVS522F–JULY 2004–REVISED AUGUST 2005
APPLICATION INFORMATION
Capacitors
Input Capacitor (CIN)
A minimum value of 1 µF (over the entire operating temperature range) is required at the input of the LP2985. In
addition, this input capacitor should be located within 1 cm of the input pin and connected to a clean analog
ground. There are no equivalent series resistance (ESR) requirements for this capacitor, and the capacitance
can be increased without limit.
Output Capacitor (COUT
)
As an advantage over other regulators, the LP2985 permits the use of low-ESR capacitors at the output,
including ceramic capacitors that can have an ESR as low as 5 mΩ. Tantalum and film capacitors also can be
used if size and cost are not issues. The output capacitor also should be located within 1 cm of the output pin
and be returned to a clean analog ground.
As with other PNP LDOs, stability conditions require the output capacitor to have a minimum capacitance and an
ESR that falls within a certain range.
•
•
Minimum COUT: 2.2 µF (can be increased without limit to improve transient response stability margin)
ESR range: see Figure 28
Load Current − mA
Figure 28. 2.2-V/3.3-µF ESR Curves
It is critical that both the minimum capacitance and ESR requirement be met over the entire operating
temperature range. Depending on the type of capacitors used, both these parameters can vary significantly with
temperature (see capacitor characteristics).
Noise Bypass Capacitor (CBYPASS
)
The LP2985 allows for low-noise performance with the use of a bypass capacitor that is connected to the internal
bandgap reference via the BYPASS pin. This high-impedance bandgap circuitry is biased in the microampere
range and, thus, cannot be loaded significantly, otherwise, its output – and, correspondingly, the output of the
regulator – changes. Thus, for best output accuracy, dc leakage current through CBYPASS should be minimized as
much as possible and never should exceed 100 nA.
A 10-nF capacitor is recommended for CBYPASS. Ceramic and film capacitors are well suited for this purpose.
14
LP2985
150-mA LOW-NOISE LOW-DROPOUT REGULATOR
WITH SHUTDOWN
www.ti.com
SLVS522F–JULY 2004–REVISED AUGUST 2005
APPLICATION INFORMATION (continued)
Capacitor Characteristics
Ceramics
Ceramic capacitors are ideal choices for use on the output of the LP2985 for several reasons. For capacitances
in the range of 2.2 µF to 4.7 µF, ceramic capacitors have the lowest cost and the lowest ESR, making them
choice candidates for filtering high-frequency noise. For instance, a typical 2.2-µF ceramic capacitor has an ESR
in the range of 10 mΩ to 20 mΩ and, thus, satisfies minimum ESR requirements of the regulator.
Ceramic capacitors have one major disadvantage that must be taken into account – a poor temperature
coefficient, where the capacitance can vary significantly with temperature. For instance, a large-value ceramic
capacitor (≥2.2 µF) can lose more than half of its capacitance as the temperature rises from 25°C to 85°C. Thus,
a 2.2-µF capacitor at 25°C drops well below the minimum COUT required for stability, as ambient temperature
rises. For this reason, select an output capacitor that maintains the minimum 2.2 µF required for stability over the
entire operating temperature range. Note that there are some ceramic capacitors that can maintain a ±15%
capacitance tolerance over temperature.
Tantalum
Tantalum capacitors can be used at the output of the LP2985, but there are significant disadvantages that could
prohibit their use:
•
In the 1-µF to 4.7-µF range, tantalum capacitors are more expensive than ceramics of the equivalent
capacitance and voltage ratings.
•
Tantalum capacitors have higher ESRs than their equivalent-sized ceramic counterparts. Thus, to meet the
ESR requirements, a higher-capacitance tantalum may be required, at the expense of larger size and higher
cost.
•
The ESR of a tantalum capacitor increases as temperature drops, as much as double from 25°C to –40°C.
Thus, ESR margins must be maintained over the temperature range to prevent regulator instability.
ON/OFF Operation
The LP2985 allows for a shutdown mode via the ON/OFF pin. Driving the pin LOW (≤0.3 V) turns the device
OFF; conversely, a HIGH (≥1.6 V) turns the device ON. If the shutdown feature is not used, ON/OFF should be
connected to the input to ensure that the regulator is on at all times. For proper operation, do not leave ON/OFF
unconnected, and apply a signal with a slew rate of ≥40 mV/µs.
15
LP2985
150-mA LOW-NOISE LOW-DROPOUT REGULATOR
WITH SHUTDOWN
www.ti.com
SLVS522F–JULY 2004–REVISED AUGUST 2005
APPLICATION INFORMATION (continued)
Reverse Input-Output Voltage
There is an inherent diode present across the PNP pass element of the LP2985.
V
IN
V
OUT
With the anode connected to the output, this diode is reverse biased during normal operation, since the input
voltage is higher than the output. However, if the output is pulled higher than the input for any reason, this diode
is forward biased and can cause a parasitic silicon-controlled rectifier (SCR) to latch, resulting in high current
flowing from the output to the input. Thus, to prevent possible damage to the regulator in any application where
the output may be pulled above the input, an external Schottky diode should be connected between the output
and input. With the anode on output, this Schottky limits the reverse voltage across the output and input pins to
0.3 V, preventing the regulator’s internal diode from forward biasing.
Schottky
V
IN
V
OUT
LP2985
16
PACKAGE OPTION ADDENDUM
www.ti.com
4-Feb-2006
PACKAGING INFORMATION
Orderable Device
LP2985-28DBVR
LP2985-28DBVRE4
LP2985-28DBVT
LP2985-28DBVTE4
Status (1)
ACTIVE
ACTIVE
ACTIVE
ACTIVE
Package Package
Pins Package Eco Plan (2) Lead/Ball Finish MSL Peak Temp (3)
Qty
Type
Drawing
SOT-23
DBV
5
5
5
5
3000 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
SOT-23
SOT-23
SOT-23
DBV
DBV
DBV
3000 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
250 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
250 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
LP2985-28YEQR
LP2985-28YEUR
LP2985-28YZQR
LP2985-28YZUR
LP2985-33DBVR
PREVIEW
PREVIEW
PREVIEW
PREVIEW
ACTIVE
DSBGA
DSBGA
DSBGA
DSBGA
SOT-23
YEQ
YEU
YZQ
YZU
DBV
5
5
5
5
5
3000
3000
3000
3000
TBD
TBD
TBD
TBD
Call TI
Call TI
Call TI
Call TI
Call TI
Call TI
Call TI
Call TI
3000 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
LP2985-33DBVRE4
LP2985-33DBVT
ACTIVE
ACTIVE
ACTIVE
SOT-23
SOT-23
SOT-23
DBV
DBV
DBV
5
5
5
3000 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
250 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
LP2985-33DBVTE4
250 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
LP2985-33YEQR
LP2985-33YEUR
LP2985-33YZQR
LP2985-33YZUR
LP2985-50DBVR
LP2985-50DBVT
LP2985A-18DBVR
PREVIEW
PREVIEW
PREVIEW
PREVIEW
PREVIEW
PREVIEW
ACTIVE
DSBGA
DSBGA
DSBGA
DSBGA
SOT-23
SOT-23
SOT-23
YEQ
YEU
YZQ
YZU
DBV
DBV
DBV
5
5
5
5
5
5
5
3000
3000
3000
3000
3000
250
TBD
TBD
TBD
TBD
TBD
TBD
Call TI
Call TI
Call TI
Call TI
Call TI
Call TI
Call TI
Call TI
Call TI
Call TI
Call TI
Call TI
3000 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
LP2985A-18DBVRE4
LP2985A-18DBVT
LP2985A-18DBVTE4
LP2985A-28DBVR
LP2985A-28DBVRE4
LP2985A-28DBVT
LP2985A-28DBVTE4
LP2985A-33DBVR
LP2985A-33DBVRE4
LP2985A-33DBVT
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
SOT-23
SOT-23
SOT-23
SOT-23
SOT-23
SOT-23
SOT-23
SOT-23
SOT-23
SOT-23
DBV
DBV
DBV
DBV
DBV
DBV
DBV
DBV
DBV
DBV
5
5
5
5
5
5
5
5
5
5
3000 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
250 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
250 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
3000 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
3000 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
250 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
250 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
3000 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
3000 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
250 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
Addendum-Page 1
PACKAGE OPTION ADDENDUM
www.ti.com
4-Feb-2006
Orderable Device
Status (1)
Package Package
Pins Package Eco Plan (2) Lead/Ball Finish MSL Peak Temp (3)
Qty
Type
Drawing
LP2985A-33DBVTE4
ACTIVE
SOT-23
DBV
5
250 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check
http://www.ti.com/productcontent for the latest availability information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and
package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS
compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame
retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
Addendum-Page 2
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications,
enhancements, improvements, and other changes to its products and services at any time and to discontinue
any product or service without notice. Customers should obtain the latest relevant information before placing
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TI warrants performance of its hardware products to the specifications applicable at the time of sale in
accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI
deems necessary to support this warranty. Except where mandated by government requirements, testing of all
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TI assumes no liability for applications assistance or customer product design. Customers are responsible for
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