TI LP2985-18DBVT 150-ma low-noise low-dropout regulator with shutdown Datasheet

LP2985
150-mA LOW-NOISE LOW-DROPOUT REGULATOR
WITH SHUTDOWN
www.ti.com
SLVS522F – JULY 2004 – REVISED AUGUST 2005
FEATURES
PORTABLE APPLICATIONS
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Output Tolerance of
– 1% (A Grade)
– 1.5% (Standard Grade)
Ultra-Low Dropout, Typically
– 280 mV at Full Load of 150 mA
– 7 mV at 1 mA
Wide VIN Range…16 V Max
Low IQ . . . 850 µA at Full Load at 150 mA
Shutdown Current . . . 0.01 µA Typ
Low Noise . . . 30 µVRMS With 10-nF Bypass
Capacitor
Stable With Low-ESR Capacitors, Including
Ceramic
Overcurrent and Thermal Protection
High Peak-Current Capability
Cellular Phones
Palmtop and Laptop Computers
Personal Digital Assistants (PDAs)
Digital Cameras and Camcorders
CD Players
MP3 Players
DBV (SOT-23) PACKAGE
(TOP VIEW)
VIN
GND
ON/OFF
1
5
VOUT
4
BYPASS
2
3
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
TJ
PART
GRADE
VOUT
(NOM)
PACKAGE (1)
1.8 V
2.8 V
2.9 V
A grade:
1% tolerance
3.0 V
3.3 V
5.0 V
–40°C to 125°C
SOT-23-5 – DBV
1.8 V
2.8 V
2.9 V
Standard grade:
1.5% tolerance
3.0 V
3.3 V
5.0 V
(1)
(2)
2
ORDERABLE
PART NUMBER
Reel of 3000
LP2985A-18DBVR
Reel of 250
LP2985A-18DBVT
Reel of 3000
LP2985A-28DBVR
Reel of 250
LP2985A-28DBVT
Reel of 3000
LP2985A-29DBVR
Reel of 250
LP2985A-29DBVT
Reel of 3000
LP2985A-30DBVR
Reel of 250
LP2985A-30DBVT
Reel of 3000
LP2985A-33DBVR
Reel of 250
LP2985A-33DBVT
Reel of 3000
LP2985A-50DBVR
Reel of 250
LP2985A-50DBVT
Reel of 3000
LP2985-18DBVR
Reel of 250
LP2985-18DBVT
Reel of 3000
LP2985-28DBVR
Reel of 250
LP2985-28DBVT
Reel of 3000
LP2985-29DBVR
Reel of 250
LP2985-29DBVT
Reel of 3000
LP2985-30DBVR
Reel of 250
LP2985-30DBVT
Reel of 3000
LP2985-33DBVR
Reel of 250
LP2985-33DBVT
Reel of 3000
LP2985-50DBVR
Reel of 250
LP2985-50DBVT
TOP-SIDE
MARKING (2)
LPT3
LPJ3
PREVIEW
PREVIEW
LPK3
PREVIEW
LPH3
LPG3
PREVIEW
PREVIEW
LPF3
PREVIEW
Package drawings, standard packing quantities, thermal data, symbolization, and PCB design guidelines are available at
www.ti.com/sc/package.
The actual top-side marking has one additional character that designates the assembly/test site.
LP2985
150-mA LOW-NOISE LOW-DROPOUT REGULATOR
WITH SHUTDOWN
www.ti.com
SLVS522F – JULY 2004 – REVISED AUGUST 2005
FUNCTIONAL BLOCK DIAGRAM
VIN
ON/OFF
1.23 V
VREF
−
+
BYPASS
VOUT
Overcurrent/
Overtemperature
Protection
BASIC APPLICATION CIRCUIT
LP2985
VIN
1
VOUT
5
2.2 µF
(see Note A)
1 µF
(see Note A)
GND
2
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
MAX
VIN
Continuous input voltage range
–0.3
16
V
VON/OFF
ON/OFF input voltage range
–0.3
16
V
range (2)
–0.3
9
V
Input/output voltage differential range (3)
–0.3
16
V
Output voltage
VIN – VOUT
UNIT
Internally limited
(short-circuit protected)
IO
Output current (4)
θJA
Package thermal impedance (4) (5)
206
°C/W
TJ
Operating virtual junction temperature
150
°C
Tstg
Storage temperature range
150
°C
(1)
(2)
(3)
(4)
(5)
–65
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.
If load is returned to a negative power supply in a dual-supply system, the output must be diode clamped to GND.
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).
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.
The package thermal impedance is calculated in accordance with JESD 51-7.
Recommended Operating Conditions
VIN
Supply input voltage
VON/OFF
ON/OFF input voltage
IOUT
Output current
TJ
Virtual junction temperature
(1)
4
MIN
MAX
2.2 (1)
16
0
VIN
V
150
mA
125
°C
–40
Recommended minimum VIN is the greater of 2.5 V or VOUT(max) + rated dropout voltage (max) for operating IL.
UNIT
V
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)
PARAMETER
TEST CONDITIONS
IL = 1 mA
∆VOUT
Output
voltage
tolerance
1 mA ≤ IL ≤ 50 mA
1 mA ≤ IL ≤ 150 mA
Line
regulation
VIN = [VOUT(NOM) + 1 V] to 16 V
IL = 0
IL = 1 mA
VIN – VOUT
Dropout
voltage (1)
IL = 10 mA
IL = 50 mA
IL = 150 mA
IL = 0
IL = 1 mA
IL = 10 mA
IGND
Ground
pin
current
IL = 50 mA
IL = 150 mA
VON/OFF < 0.3 V (OFF)
VON/OFF < 0.15 V (OFF)
VON/OFF
ION/OFF
ON/OFF
input
voltage (2)
ON/OFF
input
current
VON/OFF = HIGH → O/P ON
VON/OFF = LOW → O/P OFF
VON/OFF = 0
VON/OFF = 5 V
TJ
LP2985A-xx
MIN
TYP
LP2985-xx
MAX
MIN
TYP
MAX
UNIT
25°C
–1
1
–1.5
1.5
25°C
–1.5
1.5
–2.5
2.5
–40°C to 125°C
–2.5
2.5
–3.5
3.5 %VNOM
25°C
–2.5
2.5
–3
3
–40°C to 125°C
–3.5
3.5
–4
4
25°C
0.007
–40°C to 125°C
0.014
0.007
0.032
25°C
1
3
7
10
–40°C to 125°C
0.032
1
3
7
10
5
25°C
–40°C to 125°C
40
–40°C to 125°C
15
60
40
90
25°C
120
–40°C to 125°C
25°C
280
150
120
65
–40°C to 125°C
350
280
75
–40°C to 125°C
65
120
–40°C to 125°C
75
350
–40°C to 125°C
120
25°C
850
110
220
400
600
350
1000
–40°C to 125°C
95
170
220
400
25°C
350
125
110
170
25°C
150
575
95
125
25°C
600
1500
850
1500
2500
25°C
0.01
0.8
0.01
0.8
–40°C to 105°C
0.05
2
0.05
2
5
25°C
–40°C to 125°C
25°C
25°C
1.4
1.6
1.6
0.55
0.15
0.15
0.01
–2
5
–40°C to 125°C
V
0.55
0.01
–40°C to 125°C
25°C
5
1.4
–40°C to 125°C
µA
1000
2500
–40°C to 125°C
mV
225
575
25°C
60
90
225
–40°C to 125°C
%/V
5
15
25°C
0.014
–2
5
15
µA
15
Vn
Output
noise
(RMS)
BW = 300 Hz to 50 kHz,
COUT = 10 µF,
CBYPASS = 10 nF
25°C
30
30
µV
∆VOUT/∆VIN
Ripple
rejection
f = 1kHz, COUT = 10 µF,
CBYPASS = 10 nF
25°C
45
45
dB
(1)
(2)
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.
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)
PARAMETER
TEST CONDITIONS
TJ
LP2985A-xx
MIN
TYP
LP2985-xx
MAX
MIN
TYP
MAX
UNIT
IOUT(PK)
Peak output
VOUT ≥ VO(NOM) – 5%
current
25°C
350
350
mA
IOUT(SC)
Short-circuit
RL = 0 (steady state) (3)
current
25°C
400
400
mA
(3)
6
See Figure 5 in Typical Performance Characteristics.
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
3.345
VI = 4.3 V
VO = 3.3 V
Ci = 1 µF
Co = 4.7 µF
IO = 1 mA
150 mA
VO = 3.3 V
Cbyp = 10 nF
0.35
0.3
Dropout − V
Output Voltage − V
3.335
0.4
3.325
3.315
0.25
0.2
50 mA
0.15
0.1
3.305
10 mA
0.05
1 mA
3.295
−50
−25
0
25
50
75
100
125
0
−50
150
−25
0
Temperature − °C
0.45
Short-Circuit Current − A
0.4
Figure 2.
SHORT-CIRCUIT CURRENT
vs
TIME
SHORT-CIRCUIT CURRENT
vs
TIME
0.5
VI = 6 V
VO = 3.3 V
Ci = 1 µF
Cbyp = 0.01 µF
0.3
0.25
0.2
0.15
0.4
0.3
0.25
0.2
0.15
0.1
0.05
0.05
500
1000
Time − ms
Figure 3.
1500
2000
150
0.35
0.1
0
125
VI = 16 V
VO = 3.3 V
Ci = 1 µF
Cbyp = 0.01 µF
0.45
0.35
0
−500
100
Figure 1.
Short-Circuit Current − A
0.5
25
50
75
Temperature − °C
0
−100
100
300
Time − ms
500
700
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
OUTPUT VOLTAGE
GROUND-PIN CURRENT
vs
LOAD CURRENT
1200
320
VO = 3.3 V
300
1000
900
Ground Pin Current − µA
280
ISC − mA
VO = 3.3 V
Cbyp = 10 nF
1100
260
240
800
700
600
500
400
300
200
220
100
200
0
0
0.5
1
1.5
2
2.5
Output Voltage − V
3
3.5
60
80
100
Load Current − mA
Figure 6.
RIPPLE REJECTION
vs
FREQUENCY
RIPPLE REJECTION
vs
FREQUENCY
120
140
160
100
VI = 5 V
VO = 3.3 V
Co = 10 µF
Cbyp = 0 nF
80
70
80
50 mA
1 mA
60
50
40
150 mA
30
70
1 mA
60
50
30
20
10
10
0
100
1k
10k
Frequency − Hz
Figure 7.
100k
1M
50 mA
40
20
10
VI = 3.7 V
VO = 3.3 V
Co = 10 µF
Cbyp = 0 nF
90
Ripple Rejection − dB
90
Ripple Rejection − dB
40
Figure 5.
100
8
20
0
150 mA
0
10
100
1k
10k
Frequency − Hz
Figure 8.
100k
1M
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
FREQUENCY
RIPPLE REJECTION
vs
FREQUENCY
100
100
VI = 5 V
VO = 3.3 V
Co = 4.7 µF
Cbyp = 10 nF
Ripple Rejection − dB
80
80
70
1 mA
60
50
40
50 mA
30
20
VI = 5 V
VO = 3.3 V
Co = 4.7 µF
Cbyp = 10 nF
90
Ripple Rejection − dB
90
70
1 mA
60
10 mA
50
40
100 mA
30
20
150 mA
10
10
0
0
10
100
1k
10k
100k
10
1M
100
Frequency − Hz
1
Figure 9.
Figure 10.
OUTPUT IMPEDANCE
vs
FREQUENCY
OUTPUT IMPEDANCE
vs
FREQUENCY
Ci = 1 µF
Co = 10 µF
VO = 3.3 V
1 mA
Output Impedance − Ω
Output Impedance − Ω
10
10 mA
100 mA
0.1
0.01
0.001
10
100
1k
10k
Frequency − Hz
1k
10k
Frequency − Hz
Figure 11.
100k
1M
10
Ci = 1 µF
Co = 4.7 µF
VO = 3.3 V
1
1 mA
100k
1M
100k
1M
10 mA
100 mA
0.1
0.01
0.001
10
100
1k
10k
Frequency − Hz
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
vs
FREQUENCY
OUTPUT NOISE DENSITY
vs
FREQUENCY
10
10
ILOAD = 1 mA
Hz
1
Noise Density − nV/
Noise Density − nV/ Hz
ILOAD = 150 mA
Cbyp = 100 nF
Cbyp = 1 nF
0.1
Cbyp = 10 nF
1
Cbyp = 100 nF
Cbyp = 1 nF
0.1
Cbyp = 10 nF
0.01
0.01
100
1k
10k
Frequency − Hz
100
100k
1k
10k
Frequency − Hz
Figure 13.
Figure 14.
INPUT CURRENT
vs
INPUT VOLTAGE
GROUND-PIN CURRENT
vs
TEMPERATURE
1.8
100k
1400
VO = 3.3 V
Cbyp = 10 nF
1.6
RL = 3.3 kΩ
1200
VO = 3.3 V
Cbyp = 10 nF
150 mA
Ground Current − C
Input Current − mA
1.4
1.2
1
0.8
RL = Open
0.6
1000
800
600
1 mA
400
50 mA
0.4
0 mA
200
0.2
0
0
1
2
3
4
Input Voltage − V
Figure 15.
10
5
6
10 mA
0
−50
−25
0
25
50
75
Temperature − °C
Figure 16.
100
125
150
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)
200
3.38
150
3.38
150
3.36
100
3.36
100
3.32
3.3
50
IL
VO = 3.3 V
Cbyp = 10 nF
∆IL = 100 mA
0
−50
VO
3.28
−100
3.26
−150
3.24
−200
3.22
−250
IL
3.34
3.32
3.3
VO = 3.3 V
Cbyp = 10 nF
∆IL = 150 mA
0
−50
VO
3.28
−100
3.26
−150
3.24
−200
3.22
−250
20 µs/div
20 µs/div
Figure 17.
Figure 18.
LOAD TRANSIENT RESPONSE
LINE TRANSIENT RESPONSE
3.4
200
3.38
150
3.36
100
3.41
5.5
3.39
5
VI
3.32
3.3
VO = 3.3 V
Cbyp = 0 nF
∆IL = 150 mA
50
0
−50
VO
3.28
−100
3.26
−150
3.24
−200
3.22
−250
20 µs/div
Figure 19.
Output Voltage − V
IL
Load Current − mA
Output Voltage − V
3.37
3.34
50
3.35
VO = 3.3 V
Cbyp = 0 nF
IO = 150 mA
4.5
4
3.5
3.33
3.31
VO
Input Voltage − V
3.34
Output Voltage − V
3.4
Load Current − mA
LOAD TRANSIENT RESPONSE
200
Load Current − mA
Output Voltage − V
LOAD TRANSIENT RESPONSE
3.4
3
3.29
2.5
3.27
2
20 µs/div
Figure 20.
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
3.41
5.5
3.39
5
3.39
5
4.5
3.37
3.35
VO = 3.3 V
Cbyp = 10 nF
IO = 150 mA
4
3
3.31
3
2.5
3.29
3.31
3.27
4
3.5
3.5
VO
VO = 3.3 V
Cbyp = 0 nF
IO = 1 mA
4.5
3.33
3.33
3.29
3.35
VI
Input Voltage − V
VI
3.37
Output Voltage − V
5.5
Input Voltage − V
Output Voltage − V
LINE TRANSIENT RESPONSE
3.41
2.5
VO
3.27
2
2
20 µs/div
20 µs/div
Figure 21.
Figure 22.
LINE TRANSIENT RESPONSE
TURN-ON TIME
5.5
3.41
4
10
VO
3
5
3.39
8
3.5
3.31
VO
3
1
6
0
−1
VO = 3.3 V
Cbyp = 0
IO = 150 mA
4
−2
VON/OFF
2.5
3.29
3.27
2
100 µs/div
Figure 23.
12
2
−3
−4
0
100 µs/div
Figure 24.
VON/OFF − V
3.33
VO = 3.3 V
Cbyp = 10 nF
IO = 1 mA
Output Voltage − V
Output Voltage − V
4
3.35
2
4.5
Input Voltage − V
VIN
3.37
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
4
10
4
VO
VO
3
3
8
8
0
VO = 3.3 V
Cbyp = 100 pF
ILOAD = 150 mA
4
−2
VON/OFF
1
6
0
−1
VO = 3.3 V
Cbyp = 1 nF
ILOAD = 150 mA
4
VON/OFF
−2
2
2
−3
−3
0
−4
0
−4
2 ms/div
200 µs/div
Figure 25.
Figure 26.
TURN-ON TIME
4
Input
10
3
8
2
1
6
0
−1
4
VO = 3.3 V
Cbyp = 10 nF
ILOAD = 150 mA
VON/OFF − V
−1
Output Voltage − V
6
VON/OFF − V
1
Output Voltage − V
Output Voltage − V
2
VON/OFF − V
2
Output
−2
2
−3
0
−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.
ESR − Ω
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
www.ti.com
LP2985
150-mA LOW-NOISE LOW-DROPOUT REGULATOR
WITH SHUTDOWN
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.
VIN
VOUT
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
VIN
VOUT
LP2985
16
PACKAGE OPTION ADDENDUM
www.ti.com
4-Feb-2006
PACKAGING INFORMATION
Orderable Device
Status (1)
Package
Type
Package
Drawing
Pins Package Eco Plan (2)
Qty
LP2985-28DBVR
ACTIVE
SOT-23
DBV
5
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2985-28DBVRE4
ACTIVE
SOT-23
DBV
5
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2985-28DBVT
ACTIVE
SOT-23
DBV
5
250
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2985-28DBVTE4
ACTIVE
SOT-23
DBV
5
250
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2985-28YEQR
PREVIEW
DSBGA
YEQ
5
3000
TBD
Call TI
Call TI
LP2985-28YEUR
PREVIEW
DSBGA
YEU
5
3000
TBD
Call TI
Call TI
LP2985-28YZQR
PREVIEW
DSBGA
YZQ
5
3000
TBD
Call TI
Call TI
LP2985-28YZUR
PREVIEW
DSBGA
YZU
5
3000
TBD
Call TI
Call TI
LP2985-33DBVR
ACTIVE
SOT-23
DBV
5
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2985-33DBVRE4
ACTIVE
SOT-23
DBV
5
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2985-33DBVT
ACTIVE
SOT-23
DBV
5
250
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2985-33DBVTE4
ACTIVE
SOT-23
DBV
5
250
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2985-33YEQR
PREVIEW
DSBGA
YEQ
5
3000
TBD
Call TI
Call TI
LP2985-33YEUR
PREVIEW
DSBGA
YEU
5
3000
TBD
Call TI
Call TI
LP2985-33YZQR
PREVIEW
DSBGA
YZQ
5
3000
TBD
Call TI
Call TI
LP2985-33YZUR
PREVIEW
DSBGA
YZU
5
3000
TBD
Call TI
Call TI
LP2985-50DBVR
PREVIEW
SOT-23
DBV
5
3000
TBD
Call TI
Call TI
TBD
Call TI
Call TI
Lead/Ball Finish
MSL Peak Temp (3)
LP2985-50DBVT
PREVIEW
SOT-23
DBV
5
250
LP2985A-18DBVR
ACTIVE
SOT-23
DBV
5
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2985A-18DBVRE4
ACTIVE
SOT-23
DBV
5
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2985A-18DBVT
ACTIVE
SOT-23
DBV
5
250
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2985A-18DBVTE4
ACTIVE
SOT-23
DBV
5
250
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2985A-28DBVR
ACTIVE
SOT-23
DBV
5
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2985A-28DBVRE4
ACTIVE
SOT-23
DBV
5
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2985A-28DBVT
ACTIVE
SOT-23
DBV
5
250
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2985A-28DBVTE4
ACTIVE
SOT-23
DBV
5
250
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2985A-33DBVR
ACTIVE
SOT-23
DBV
5
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2985A-33DBVRE4
ACTIVE
SOT-23
DBV
5
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2985A-33DBVT
ACTIVE
SOT-23
DBV
5
250
CU NIPDAU
Level-1-260C-UNLIM
Addendum-Page 1
Green (RoHS &
no Sb/Br)
PACKAGE OPTION ADDENDUM
www.ti.com
4-Feb-2006
Orderable Device
Status (1)
Package
Type
Package
Drawing
LP2985A-33DBVTE4
ACTIVE
SOT-23
DBV
Pins Package Eco Plan (2)
Qty
5
250
Green (RoHS &
no Sb/Br)
Lead/Ball Finish
CU NIPDAU
MSL Peak Temp (3)
Level-1-260C-UNLIM
(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.
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Addendum-Page 2
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