REG101NA-5/2K5 [ETC]
Positive Fixed Voltage Regulator ; 正固定电压稳压器\n
| 型号： | REG101NA-5/2K5 |
| 厂家： | 
ETC |
| 描述： | Positive Fixed Voltage Regulator
|
| 文件： | 总14页 (文件大小：267K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
REG101
REG101
www.ti.com
DMOS
100mA Low-Dropout Regulator
DESCRIPTION
FEATURES
The REG101 is a family of low noise, low dropout
linear regulators with low ground pin current. Its new
DMOS topology provides significant improvement
over previous designs, including low dropout voltage
(only 60mV typ at full load), and better transient
performance. In addition, no output capacitor is re-
quired for stability, unlike conventional low dropout
regulators that are difficult to compensate and require
expensive low ESR capacitors greater than 1µF.
● NEW DMOS TOPOLOGY:
Ultra Low Dropout Voltage:
60mV typ at 100mA
Output capacitor NOT required for stability
● FAST TRANSIENT RESPONSE
●
VERY LOW NOISE: 23µVrms
● HIGH ACCURACY: ±1.5% max
● HIGH EFFICIENCY:
Typical ground pin current is only 500µA (at IOUT
=
IGND = 500µA at IOUT = 100mA
Not Enabled: IGND = 10nA
100mA) and drops to 10nA when not enabled mode.
Unlike regulators with PNP pass devices, quiescent
current remains relatively constant over load variation
and under dropout conditions.
● 2.5V, 2.8V, 2.85V, 3.0V, 3.3V, 5.0V AND
ADJUSTABLE OUTPUT VERSIONS
The REG101 has very low output noise (typically
23µVrms for VOUT = 3.3V with CNR = 0.01µF),
making it ideal for use in portable communications
equipment. Accuracy is maintained over temperature,
line, and load variations. Key parameters are guaran-
teed over the specified temperature range
(–40°C to +85°C).
● OTHER OUTPUT VOLTAGES AVAILABLE
UPON REQUEST
● FOLDBACK CURRENT LIMIT
● THERMAL PROTECTION
● SMALL SURFACE-MOUNT PACKAGES:
SOT23-5 and SO-8
The REG101 is well protected—internal circuitry pro-
vides a current limit which protects the load from
damage. Thermal protection circuitry keeps the chip
from being damaged by excessive temperature. The
REG101 is available in the SOT23-5 and the SO-8
packages.
APPLICATIONS
● PORTABLE COMMUNICATION DEVICES
● BATTERY-POWERED EQUIPMENT
● PERSONAL DIGITAL ASSISTANTS
● MODEMS
● BAR-CODE SCANNERS
● BACKUP POWER SUPPLIES
Enable
Enable
VOUT
VIN
VOUT
VIN
REG101
(Fixed Voltage
Versions)
+
R1
Adj
R2
+
+
+
0.1µF
(1)
(1)
COUT
REG101-A
COUT
0.1µF
NR
Gnd
Gnd
NR = Noise Reduction
NOTE: (1) Optional.
Copyright © 2000, Texas Instruments Incorporated
SBVS026B
Printed in U.S.A. February, 2001
SPECIFICATIONS
Boldface limits apply over the specified temperature range, TJ = –40°C to +85°C.
At TJ = +25°C, VIN = VOUT + 1V (VOUT = 2.5V for REG101-A), VENABLE = 1.8V, IOUT = 2mA, CNR = 0.01µF, and COUT = 0.1µF(1), unless otherwise noted.
REG101NA
REG101UA
PARAMETER
CONDITION
MIN
TYP
MAX
UNITS
OUTPUT VOLTAGE
Output Voltage
REG101-2.5
REG101-2.8
REG101-2.85
REG101-3.0
REG101-3.3
REG101-5
REG101-A
VOUT
2.5
2.8
2.85
3.0
3.3
5
V
V
V
V
V
V
V
2.5
5.5
Reference Voltage
Adjust Pin Current
Accuracy
Over Temperature
vs Temperature
Includes Line and Load
Over Temperature
VREF
IADJ
1.267
0.2
±0.5
V
µA
%
%
ppm/°C
%
1
±1.5
±2.2
dVOUT/dT
VDROP
Vn
50
±0.8
IOUT = 2mA to 100mA, VIN = (VOUT + 0.4V) to 10V
±2.0
±2.7
VIN = (VOUT + 0.6V) to 10V
%
DC DROPOUT VOLTAGE(2)
For all models
Over Temperature
IOUT = 2mA
IOUT = 100mA
IOUT = 100mA
4
60
10
100
130
mV
mV
mV
VOLTAGE NOISE
Without CNR
With CNR (all fixed voltage models)
f = 10Hz to 100kHz
CNR = 0, COUT = 0
CNR = 0.01µF, COUT = 10µF
23µVrms/V • VOUT
7µVrms/V • VOUT
µVrms
µVrms
OUTPUT CURRENT
Current Limit(3)
Over Temperature
Short Circuit Current
ICL
ISC
130
110
170
60
220
240
mA
mA
mA
RIPPLE REJECTION
f = 120Hz
IOUT = 100mA
65
dB
ENABLE CONTROL
V
ENABLE High (output enabled)
VENABLE Low (output disabled)
ENABLE High (output enabled)
VENABLE
IENABLE
1.8
–0.2
VIN
0.5
100
100
V
V
nA
nA
µs
ms
I
VENABLE = 1.8V to VIN, VIN = 1.8V to 6.5
VENABLE = 0V to 0.5V
1
2
200
1.5
IENABLE Low (output disabled)
Output Disable Time
Output Enable Time
COUT = 1.0µF, RLOAD = 33Ω
COUT = 1.0µF, RLOAD = 33Ω
THERMAL SHUTDOWN
Junction Temperature
Shutdown
160
140
°C
°C
Reset from Shutdown
GROUND PIN CURRENT
Ground Pin Current
IGND
IOUT = 2mA
IOUT = 100mA
VENABLE ≤ 0.5V
400
500
0.01
500
650
0.2
µA
µA
µA
Enable Pin Low
INPUT VOLTAGE
VIN
Operating Input Voltage Range(4)
Specified Input Voltage Range
Over Temperature
1.8
VOUT + 0.4
VOUT + 0.6
10
10
10
V
V
V
V
IN > 1.8V
VIN > 1.8V
TEMPERATURE RANGE
Specified Range
Operating Range
TJ
TJ
TA
–40
–55
–65
+85
+125
+150
°C
°C
°C
Storage Range
Thermal Resistance
SOT23-5 Surface Mount
SO-8 Surface Mount
θJA
θJA
Junction-to-Ambient
Junction-to-Ambient
200
150
°C/W
°C/W
NOTES:(1)TheREG101doesnotrequireaminimumoutputcapacitorforstability. However, transientresponsecanbeimprovedwithpropercapacitorselection. (2)Dropout
voltage is defined as the input voltage minus the output voltage that produces a 2% change in the output voltage from the value at VIN = VOUT + 1V at fixed load. (3) Current
limit is the output current that produces a 10% change in output voltage from VIN = VOUT + 1V and IOUT = 2mA. (4) The REG101 no longer regulates when VIN < VOUT + VDROP
(MAX). In drop-out the impedance from VIN to VOUT is typically less than 1Ω at TJ = +25°C.
REG101
SBVS026B
2
PIN CONFIGURATIONS
Top View
SO-8
SOT23-5
(2)
(2)
(3)
(3)
VOUT
VOUT
1
2
3
4
8
7
6
5
VIN
VIN
GND
1
2
3
5
4
VOUT
VIN
NR/Adjust(1)
GND
NC
Enable
NR/Adjust(1)
Enable
(N Package)
(U Package)
NOTE: (1) For REG101A-A: voltage setting resistor pin. All other models: noise reduction capacitor pin.
(2) Both pin 1 and pin 2 must be connected.
(3) Both pin 7 and pin 8 must be connected.
ABSOLUTE MAXIMUM RATINGS(1)
ELECTROSTATIC
DISCHARGE SENSITIVITY
This integrated circuit can be damaged by ESD. Burr-Brown
recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling
and installation procedures can cause damage.
Supply Input Voltage, VIN .......................................................–0.3V to 12V
Enable Input ............................................................................ –0.3V to VIN
Output Short-Circuit Duration ...................................................... Indefinite
Operating Temperature Range (TJ) ................................ –55°C to +125°C
Storage Temperature Range (TA) ................................... –65°C to +150°C
Lead Temperature (soldering, 3s, SOT23-5, and SO-8) ..................... +240°C
NOTE: (1) Stresses above these ratings may cause permanent damage.
Exposure to absolute maximum conditions for extended periods may degrade
device reliability.
ESD damage can range from subtle performance degrada-
tion to complete device failure. Precision integrated circuits
may be more susceptible to damage because very small
parametric changes could cause the device not to meet its
published specifications.
REG101
SBVS026B
3
PACKAGE/ORDERING INFORMATION
PACKAGE
DRAWING
NUMBER
PACKAGE
MARKING
ORDERING
NUMBER(1)
TRANSPORT
MEDIA
PRODUCT
PACKAGE
5V Output
REG101NA-5
SOT23-5
331
R01B
REG101NA-5/250
Tape and Reel
"
"
SO-8
"
"
182
"
"
REG101NA-5/2K5
REG101UA-5
REG101UA-5/2K5
Tape and Reel
Rails
Tape and Reel
REG101UA-5
REG101U50
"
"
3.3V Output
REG101NA-3.3
SOT23-5
331
R01C
REG101NA-3.3/250
Tape and Reel
"
"
SO-8
"
"
182
"
"
REG101NA-3.3/2K5
REG101UA-3.3
REG101UA-3.3/2K5
Tape and Reel
Rails
Tape and Reel
REG101UA-3.3
REG101U33
"
"
3V Output
REG101NA-3
SOT23-5
331
R01D
REG101NA-3/250
Tape and Reel
"
"
SO-8
"
"
182
"
"
REG101NA-3/2K5
REG101UA-3
REG101UA-3/2K5
Tape and Reel
Rails
Tape and Reel
REG101UA-3
REG101U30
"
"
2.85V Output
REG101NA-2.85
SOT23-5
331
R01N
REG101NA-2.85/250
Tape and Reel
"
"
SO-8
"
"
182
"
"
REG101NA-2.85/2K5
REG101UA-2.85
REG101UA-2.85/2K5
Tape and Reel
Rails
Tape and Reel
REG101UA-2.85
REG101285
"
"
2.8V Output
REG101NA-2.8
SOT23-5
331
R01E
REG101NA-2.8/250
Tape and Reel
"
"
SO-8
"
"
182
"
"
REG101NA-2.8/2K5
REG101UA-2.8
REG101UA-2.8/2K5
Tape and Reel
Rails
Tape and Reel
REG101UA-2.8
REG101U28
"
"
2.5V Output
REG101NA-2.5
SOT23-5
331
R01G
REG101NA-2.5/250
Tape and Reel
"
"
SO-8
"
"
182
"
"
REG101NA-2.5/2K5
REG101UA-2.5
REG101UA-2.5/2K5
Tape and Reel
Rails
Tape and Reel
REG101UA-2.5
REG101U25
"
"
Adjustable Output
REG101NA-A
SOT23-5
331
R01A
REG101NA-A/250
Tape and Reel
"
"
SO-8
"
"
182
"
"
REG101NA-A/2K5
REG101UA-A
REG101UA-A/2K5
Tape and Reel
Rails
Tape and Reel
REG101UA-A
REG101UA
"
"
NOTE: (1) Models with a slash (/) are available only in Tape and Reel in the quantities indicated (e.g., /2K5 indicates 2500 devices per reel). Ordering 2500 pieces
of “REG101UA-5/2K5” will get a single 2500-piece Tape and Reel.
Many custom output voltage versions, from 2.5V to 5.1V in 50mV increments, are available upon request. Minimum order
quantities apply. Contact factory for details.
REG101
SBVS026B
4
TYPICAL PERFORMANCE CURVES
For all models, at TJ = +25°C and VENABLE = 1.8V, unless otherwise noted.
OUTPUT VOLTAGE CHANGE vs IOUT
(VIN = VOUT + 1V, Output Voltage % Change
Refered to IOUT = 50mA at +25°C)
0.80
LOAD REGULATION vs TEMPERATURE
(VIN = VOUT + 1V)
0.0%
–0.1%
–0.2%
–0.3%
–0.4%
0.60
0.40
10mA < IOUT < 100mA
+25°C
0.20
+125°C
0.00
–0.20
–0.40
–55°C
–0.60
2mA < IOUT < 1000mA
–0.80
0
0
0
10 20
30 40
50
60
70 80
90 100
–50
–25
0
25
50
75
100
125
125
125
IOUT (mA)
Temperature (°C)
LINE REGULATION
(Referred to VIN = VOUT + 1V at IOUT = 50mA)
LINE REGULATION vs TEMPERATURE
IOUT = 100mA
20
15
0.10
0.08
0.06
10
IOUT = 2mA
0.04
5
0.02
IOUT = 50mA
(VOUT + 1V) < VIN < 10V
0
0.00
–0.02
–0.04
–0.06
–0.08
–0.10
–5
–10
–15
–20
IOUT = 100mA
(VOUT + 0.4V) < VIN < 10V
1
2
3
4
5
6
7
8
–50
–25
0
25
50
75
100
VIN – VOUT (V)
Temperature (°C)
DC DROPOUT VOLTAGE vs IOUT
DC DROPOUT VOLTAGE vs TEMPERATURE
IOUT = 100mA
100
80
60
40
20
0
100
80
60
40
20
0
+125°C
+25°C
–55°C
10
20
30
40
50
60
70
80
90 100
–50
–25
0
25
50
75
100
IOUT (mA)
Temperature (°C)
REG101
SBVS026B
5
TYPICAL PERFORMANCE CURVES (Cont.)
For all models, at TJ = +25°C and VENABLE = 1.8V, unless otherwise noted.
OUTPUT VOLTAGE ACCURACY HISTOGRAM
OUTPUT VOLTAGE DRIFT HISTOGRAM
18
16
14
12
10
8
30
25
20
15
10
5
6
4
2
0
0
Error (%)
VOUT Drift (ppm/°C)
OUTPUT VOLTAGE vs TEMPERATURE
(Output Voltage % Change Referred
to IOUT = 50mA at +25°C)
GROUND PIN CURRENT, NOT ENABLED
vs TEMPERATURE
0.50
0.40
1µ
100n
10n
VENABLE = 0.5V
VIN = VOUT + 1V
0.30
IOUT = 2mA
0.20
0.10
0.00
IOUT = 50mA
–0.10
–0.20
–0.30
–0.40
–0.50
1n
IOUT = 100mA
100p
–50
–25
0
25
50
75
100
125
–50
–25
0
25
50
75
100
125
Temperature (°C)
Temperature (°C)
GROUND PIN CURRENT vs IOUT
GROUND PIN CURRENT vs TEMPERATURE
VOUT = 5V
600
500
400
300
200
100
0
600
575
550
525
500
475
450
425
400
IOUT = 100mA
VOUT = 5.0V
VOUT = 3.3V
VOUT = 3.3V
VOUT = 2.5V
VOUT = 2.5V
VIN = VOUT + 1V
VIN = VOUT + 1V
–25
0
10
20 30 40
50
IOUT (mA)
60 70
80
90 100
–50
0
25
50
75
100
125
Temperature (°C)
REG101
SBVS026B
6
TYPICAL PERFORMANCE CURVES (Cont.)
For all models, at TJ = +25°C and VENABLE = 1.8V, unless otherwise noted.
RIPPLE REJECTION vs FREQUENCY
RIPPLE REJECTION vs (VIN - VOUT
REG101-3.3
)
80
70
60
50
40
30
20
10
0
30
25
20
15
10
5
IOUT = 2mA
IOUT = 2mA
OUT = 10µF
C
IOUT = 100mA
COUT = 10µF
IOUT = 100mA
Frequency = 100kHz
OUT = 10µF
IOUT = 100mA
COUT = 0µF
C
0
10
100
1k
10k
100k
1M
10M
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
VIN - VOUT (V)
1
Frequency (Hz)
RMS NOISE VOLTAGE vs COUT
REG101-5.0
RMS NOISE VOLTAGE vs CNR
60
50
40
30
20
10
0
110
100
90
80
70
60
50
40
30
20
REG101-5.0
REG101-3.3
REG101-2.5
REG101-3.3
REG101-2.5
CNR = 0µF
10Hz < BW < 100kHz
CNR = 0.01µF
10Hz < BW < 100kHz
0.1
1
10
1
10
100
1k
10k
COUT (µF)
CNR (pF)
NOISE SPECTRAL DENSITY
NOISE SPECTRAL DENSITY
10
1
10
1
IOUT = 100mA
NR = 0µF
IOUT = 100mA
NR = 0.01µF
C
C
COUT = 1µF
COUT = 1µF
COUT = 0µF
0.1
0.01
0.1
0.01
COUT = 0µF
C
OUT = 10µF
COUT = 10µF
10k 100k
10
100
1k
10k
100k
10
100
1k
Frequency (Hz)
Frequency (Hz)
REG101
SBVS026B
7
TYPICAL PERFORMANCE CURVES (Cont.)
For all models, at TJ = +25°C and VENABLE = 1.8V, unless otherwise noted.
CURRENT LIMIT vs TEMPERATURE
FOLDBACK CURRENT LIMIT
180
160
140
120
100
80
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
ICL
REG101-3.3
VIN = VOUT + 1V
ICL
ISC
ISC
60
40
–50
–25
0
25
50
75
100
125
0
20
40
60
80 100 120 140 160 180
Temperature (°C)
Output Current (mA)
LOAD TRANSIENT RESPONSE
LINE TRANSIENT RESPONSE
REG101-3.3
IN = 4.3V
REG101-3.3
OUT = 100mA
V
I
COUT = 0µF
COUT = 0
VOUT
VOUT
COUT = 10µF
VOUT
COUT = 10µF
VOUT
IOUT
100mA
10mA
5.3V
4.3V
VIN
10µs/div
50µs/div
TURN-ON
TURN-OFF
COUT = 0µF
RLOAD = 1600Ω
COUT = 10µF
RLOAD = 33Ω
COUT = 0µF
RLOAD = 33Ω
VOUT
VOUT
COUT = 1.0µF
RLOAD = 33Ω
COUT = 10µF
RLOAD = 33Ω
COUT = 0µF
RLOAD = 1600Ω
VENABLE
VENABLE
REG101-3.3
REG101-3.3
VIN = VOUT + 1V
CNR = 0.01µF
CNR = 0.01µF
250µs/div
200µs/div
REG101
SBVS026B
8
TYPICAL PERFORMANCE CURVES (Cont.)
For all models, at TJ = +25°C and VENABLE = 1.8V, unless otherwise noted.
IENABLE vs VENABLE
POWER UP/POWER DOWN
10µ
VOUT = 3.0V
RLOAD = 30Ω
1µ
100n
10n
1n
T = +25°C
T = –55°C
T = +125°C
VIN
VOUT
6
7
8
9
10
1s/div
VENABLE (V)
RMS NOISE VOLTAGE vs CADJ
ADJUST PIN CURRENT vs TEMPERATURE
80
70
60
50
40
30
20
0.350
0.300
0.250
0.200
0.150
0.100
0.050
0.000
REG101–A
VOUT = 3.3V
COUT = 0.1µF
10Hz < frequency < 100kHz
10
100
1k
10k
100k
–50
–25
0
25
50
75
100
125
CADJ (pF)
Temperature (°C)
LOAD TRANSIENT-ADJUSTABLE VERSION
COUT = 0
LINE TRANSIENT-ADJUSTABLE VERSION
COUT = 0
VOUT
200mV/div
200mV/div
VOUT
50mV/div
50mV/div
COUT = 10µF
VOUT
COUT = 10µF
VOUT
REG101–A
REG101–A
VIN = 4.3V
VOUT = 3.3V
IOUT = 100mA
CFB = 0.01µF
VOUT = 3.3V
100mA
10mA
5.3V
4.3V
VIN
IOUT
REG101
SBVS026B
9
the input supply voltage. This is recommended to improve
ripple rejection by reducing input voltage ripple.
BASIC OPERATION
The REG101 series of LDO (Low Drop-Out) linear regula-
tors offers a wide selection of fixed output voltage versions
and an adjustable output version. The REG101 belongs to a
family of new generation LDO regulators that utilize a
DMOS pass transistor to achieve ultra-low dropout perfor-
mance and freedom from output capacitor constraints. Ground
pin current remains under 650µA over all line, load and
temperature conditions. All versions have thermal and over-
current protection, including fold-back current limit.
Figure 1 shows the basic circuit connections for the fixed
voltage models. Figure 2 gives the connections for the
adjustable output version (REG101A) and example resistor
values for some commonly used output voltages. Values for
other voltages can be calculated from the equation shown in
Figure 2.
INTERNAL CURRENT LIMIT
The REG101 internal current limit has a typical value of
170mA. A foldback feature limits the short-circuit current to
a typical short-circuit value of 60mA. This helps to protect
the regulator from damage under all load conditions. A
curve of VOUT versus IOUT is given in Figure 3 and in the
Typical Performance Curves section.
The REG101 does not require an output capacitor for regu-
lator stability and is stable over most output currents and
with almost any value and type of output capacitor up to
10µF or more. For applications where the regulator output
current drops below several milliamps, stability can be
enhanced by: adding a 1kΩ to 2kΩ load resistor; using
capacitance values less than 10µF; or keeping the effective
series resistance greater than 0.05Ω including the capacitor’s
ESR and parasitic resistance in printed circuit board traces,
solder joints, and sockets.
FOLDBACK CURRENT LIMIT
3.5
Although an input capacitor is not required it is good analog
3.0
REG101-3.3
design practice to connect a 0.1µF low ESR capacitor across
2.5
2.0
ICL
1.5
Enable
1.0
ICL
REG101
Gnd NR
VIN
VOUT
In
Out
0.5
0
COUT
0.1µF
CNR
0.01µF
0
20
40
60
80 100 120 140 160 180
Output Current (mA)
Optional
FIGURE 3. Foldback Current Limit of the REG101-3.3 at
25°C.
FIGURE 1. Fixed Voltage Nominal Circuit for REG101.
Enable
3
EXAMPLE RESISTOR VALUES
5
VOUT
VOUT (V)
R1 (Ω)(1)
R2 (Ω)(1)
1
VIN
CFB
0.01µF
REG101
R1
COUT
1.267
2.5
Short
Open
IADJ
4
11.3k
1.13k
11.5k
1.15k
0.1µF
Load
Adj
R2
2
Gnd
3.0
3.3
5.0
15.8k
1.58k
11.5k
1.15k
18.7k
1.87k
11.5k
1.15k
34.0k
3.40k
11.5k
1.15k
Optional
Pin numbers for SOT23 package.
VOUT = (1 + R1/R2) • 1.267V
NOTE: (1) Resistors are standard 1% values.
To reduce current through divider, increase resistor
values (see table at right).
As the impedance of the resistor divider increases,
I
ADJ (~200nA) may introduce an error.
CFB improves noise and transient response.
FIGURE 2. Adjustable Voltage Circuit for REG101A.
10
REG101
SBVS026B
ENABLE
RMS NOISE VOLTAGE vs CNR
The Enable pin is active HIGH and compatible with stan-
dard TTL-CMOS levels. Inputs below 0.5V (max) turn the
regulator off and all circuitry is disabled. Under this condi-
tion ground pin current drops to approximately 10nA. When
a pull-up resistor is used, and operation down to VIN = 1.8V
is required, use values < 50kΩ.
110
100
90
80
70
60
50
40
30
20
REG101-5.0
REG101-2.5
REG101-3.3
OUTPUT NOISE
A precision band-gap reference is used for the internal
reference voltage, VREF. This reference is the dominant
noise source within the REG101 and it generates approxi-
mately 29µVrms in the 10Hz to 100kHz bandwidth at the
reference output. The regulator control loop gains up the
reference noise, so that the noise voltage of the regulator is
approximately given by:
CNR = 0µF
10Hz < BW < 100kHz
1
10
100
1k
10k
CNR (pF)
FIGURE 5. Output Noise vs Noise Reduction Capacitor.
R1 + R2
VOUT
VREF
VN = 29µVrms
= 29µVrms•
R2
values of COUT. See “RMS Noise Voltage vs COUT” in the
Typical Performance Curves section.
Since the value of VREF is 1.267V, this relationship reduces to:
The REG101 utilizes an internal charge pump to develop an
internal supply voltage sufficient to drive the gate of the
DMOS pass element above VIN. The charge-pump switch-
ing noise (nominal switching frequency = 2MHz) is not
measurable at the output of the regulator over most values of
µVrms
VN = 23
• VOUT
V
Connecting a capacitor, CNR, from the Noise Reduction (NR)
pin to ground, as shown in Figure 4, forms a low-pass filter for
the voltage reference. For CNR= 10nF, the total noise in the
10Hz to 100kHz bandwidth is reduced by approximately a
factor of 2.8 for VO = 3.3V. This noise reduction effect is
shown in Figure 5 and as “RMS Noise Voltage vs CNR” in the
Typical Performance Curves section.
COUT and IOUT
.
The REG101 adjustable version does not have the noise-
reduction pin available, however, the adjust pin is the sum-
ming junction of the error amplifier. A capacitor, CFB,
connected from the output to the adjust pin will reduce both
the output noise and the peak error from a load transient. See
the typical performance curves for output noise perfor-
mance.
Noise can be further reduced by carefully choosing an
output capacitor, COUT. Best overall noise performance is
achieved with very low (< 0.22µF) or very high (> 2.2µF)
VIN
NR
Low Noise
Charge Pump
(fixed output
versions only)
CNR
VREF
(optional)
(1.26V)
DMOS
Pass
Transistor
VOUT
Over Current
Over Temp
Protection
R1
R2
Enable
Adj
(Adjustable
Versions)
REG101
NOTE: R1 and R2 are internal
on fixed output versions.
FIGURE 4. Block Diagram.
REG101
SBVS026B
11
DROP-OUT VOLTAGE
TRANSIENT RESPONSE
The REG101 uses an N-channel DMOS as the “pass”
element. When the input voltage is within a few tens of
millivolts of the output voltage, the DMOS device behaves
like a resistor. Therefore, for low values of VIN to VOUT, the
regulator’s input-to-output resistance is the RdsON of the
DMOS pass element (typically 600mΩ). For static (DC)
loads, the REG101 will typically maintain regulation down
to VIN to VOUT voltage drop of 60mV at full rated output
current. In Figure 6, the bottom line (DC dropout) shows the
minimum VIN to VOUT voltage drop required to prevent
drop-out under DC load conditions.
The REG101 response to transient line and load conditions
improves at lower output voltages. The addition of a capaci-
tor (nominal value 0.47µF) from the output pin to ground
may improve the transient response. In the adjustable ver-
sion, the addition of a capacitor, CFB (nominal value 10nF),
from the output to the adjust pin will also improve the
transient response.
THERMAL PROTECTION
The REG101 has thermal shutdown circuitry that protects
the regulator from damage. The thermal protection circuitry
disables the output when the junction temperature reaches
approximately 160°C, allowing the device to cool. When the
junction temperature cools to approximately 140°C, the
output circuitry is again enabled. Depending on various
conditions, the thermal protection circuit may cycle on and
off. This limits the dissipation of the regulator, but may have
an undesirable effect on the load.
For large step changes in load current, the REG101 requires
a larger voltage drop across it to avoid degraded transient
response. The boundary of this “transient drop-out” region is
shown as the top line in Figure 6. Values of VIN to VOUT
voltage drop above this line insure normal transient re-
sponse.
In the transient dropout region between “DC” and “Tran-
sient”, transient response recovery time increases. The time
required to recover from a load transient is a function of both
the magnitude and rate of the step change in load current and
the available “headroom” VIN to VOUT voltage drop. Under
worst-case conditions (full-scale load change with VIN to
VOUT voltage drop close to DC dropout levels), the REG101
can take several hundred microseconds to re-enter the speci-
fied window of regulation.
Any tendency to activate the thermal protection circuit
indicates excessive power dissipation or an inadequate heat
sink. For reliable operation, junction temperature should be
limited to 125°C, maximum. To estimate the margin of
safety in a complete design (including heat sink), increase
the ambient temperature until the thermal protection is
triggered. Use worst-case loads and signal conditions. For
good reliability, thermal protection should trigger more than
35°C above the maximum expected ambient condition of
your application. This produces a worst-case junction tem-
perature of 125°C at the highest expected ambient tempera-
ture and worst-case load.
140
120
The internal protection circuitry of the REG101 has been
designed to protect against overload conditions. It was not
intended to replace proper heat sinking. Continuously run-
ning the REG101 into thermal shutdown will degrade reli-
ability.
Full Scale IOUT
Transient
100
80
60
40
DC
20
0
0
25
50
75
100
125
150
IOUT (mA)
FIGURE 6. Transient and DC Dropout.
REG101
SBVS026B
12
POWER DISSIPATION
Power dissipation can be minimized by using the lowest
possible input voltage necessary to assure the required
output voltage.
The REG101 is available in two different package configu-
rations. The ability to remove heat from the die is different
for each package type and, therefore, presents different
considerations in the printed circuit-board layout. The PCB
area around the device that is free of other components
moves the heat from the device to the ambient air. While it
is difficult-to-impossible to quantify all of the variables in a
thermal design of this type, performance data for several
configurations are shown in Figure 7.
REGULATOR MOUNTING
Solder pad footprint recommendations for the various
REG101 devices are presented in Application Bulletin
“Solder Pad Recommendations for Surface-Mount Devices”
(AB-132), available from the Texas Instruments web site
(www.ti.com).
Power dissipation depends on input voltage, load condition
and duty cycle. Power dissipation is equal to the product of
the average output current times the voltage across the
output element, VIN to VOUT voltage drop.
PD = (VIN – VOUT ) • IOUT(AVG)
1.2
1.0
0.8
0.6
0.4
0.3
0
CONDITIONS
SOT23-5
SO-8
PACKAGE
SOT23-5
SO-8
θJA
200°C/W
150°C/W
0
25
50
75
100
125
Ambient Temperature (°C)
FIGURE 7. Maximum Power Dissipation versus Ambient Temperature for the Various Packages.
REG101
SBVS026B
13
IMPORTANT NOTICE
Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue
any product or service without notice, and advise customers to obtain the latest version of relevant information
to verify, before placing orders, that information being relied on is current and complete. All products are sold
subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those
pertaining to warranty, patent infringement, and limitation of liability.
TI warrants performance of its products to the specifications applicable at the time of sale in accordance with
TI’sstandardwarranty. TestingandotherqualitycontroltechniquesareutilizedtotheextentTIdeemsnecessary
to support this warranty. Specific testing of all parameters of each device is not necessarily performed, except
those mandated by government requirements.
Customers are responsible for their applications using TI components.
In order to minimize risks associated with the customer’s applications, adequate design and operating
safeguards must be provided by the customer to minimize inherent or procedural hazards.
TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent
that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other
intellectual property right of TI covering or relating to any combination, machine, or process in which such
products or services might be or are used. TI’s publication of information regarding any third party’s products
or services does not constitute TI’s approval, license, warranty or endorsement thereof.
Reproduction of information in TI data books or data sheets is permissible only if reproduction is without
alteration and is accompanied by all associated warranties, conditions, limitations and notices. Representation
or reproduction of this information with alteration voids all warranties provided for an associated TI product or
service, is an unfair and deceptive business practice, and TI is not responsible nor liable for any such use.
Resale of TI’s products or services with statements different from or beyond the parameters stated by TI for
that product or service voids all express and any implied warranties for the associated TI product or service,
is an unfair and deceptive business practice, and TI is not responsible nor liable for any such use.
Also see: Standard Terms and Conditions of Sale for Semiconductor Products. www.ti.com/sc/docs/stdterms.htm
Mailing Address:
Texas Instruments
Post Office Box 655303
Dallas, Texas 75265
Copyright 2001, Texas Instruments Incorporated
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