Document Outline
- Return to TOC
- TC1070
- List of Figures
- 1. 2.45 Battery-Operated Supply
- Features
- Applications
- Typical Application
- General Description
- Ordering Information
- Pin Configuration
- Detailed Description
- Adjust Input
- Output Capacitor
- Thermal Considerations
- Absolute Maximum Ratings
- Electrical Characteristics
- Electrical Characteristics
- Pin Description
- Package Dimensions
- Sales Offices
- TC1071
- List of Figures
- 1. 2.45 Battery-Operated Supply
- Features
- Applications
- Typical Application
- General Description
- Ordering Information
- Pin Configuration
- Absolute Maximum Ratings
- Electrical Characteristics
- Electrical Characteristics
- Pin Description
- Detailed Description
- Adjust Input
- Output Capacitor
- Thermal Considerations
- Package Dimensions
- Sales Offices
TC1070
1
PRELIMINARY INFORMATION
TC1070-01
6/13/97
50mA ADJUSTABLE CMOS
LDO WITH SHUTDOWN
TC1070
FEATURES
s
Zero Ground Current for Longer Battery Life!
s
Adjustable Output Voltage
s
Very Low Dropout Voltage
s
Guaranteed 50mA Output
s
Power-Saving Shutdown Mode
s
Over-Current and Over-Temperature Protection
s
Space-Saving SOT-23A-5 Package
s
Pin Compatible with LP2980 and MIC5205 Regulators
APPLICATIONS
s
Battery Operated Systems
s
Portable Computers
s
Medical Instruments
s
Instrumentation
s
Cellular / GSM / PHS Phones
s
Linear Post-Regulator for SMPS
s
Pagers
50mA ADJUSTABLE CMOS LDO WITH SHUTDOWN
TYPICAL APPLICATION
TelCom Semiconductor reserves the right to make changes in the circuitry and specifications ot its devices.
GENERAL DESCRIPTION
The TC1070 is an adjustable LDO designed to super-
cede a variety of older (bipolar) voltage regulators. De-
signed specifically for battery-operated systems, the
TC1070's CMOS construction eliminates wasted ground
current, significantly extending battery life. Total supply
current is typically 50
A at full load (
20 to 60 times lower
than in bipolar regulators!).
TC1070 key features include ultra low noise operation
very low dropout voltage (typically 100mV at full load) and
internal feed-forward compensation for fast response to
step changes in load. Supply current is reduced to less than
1
A when the shutdown input is low. The TC1070 incorpo-
rates both over-temperature and over-current protection.
Output voltage is programmed with a simple resistor divider
from V
OUT
to ADJ.
The TC1070 is stable with an output capacitor of only
1
F and has a maximum output current of 50mA. For higher
output versions, please see the TC1107, TC1108
(I
OUT
= 300mA) data sheets.
C1
1
F
Shutdown Control
(from Power Control Logic)
TC1070
V
IN
1
2
3
4
R2
R1
5
V
IN
V
OUT
ADJ
V
OUT
= V
REF
x
[
R2 + 1
]
R1
SHDN
GND
V
OUT
PIN CONFIGURATION
ORDERING INFORMATION
Output
Junction
Part No.
Voltage **(V) Package
Temp. Range
TC1070VCT
Adjustable
SOT-23A-5* 40
C to +125
C
NOTE: *SOT-23A-5 is equivalent to the EIAJ (SC-74A)
** Other output voltages available. Please contact TelCom
Semiconductor for details
NOTE: *SOT-23A-5 is equivalent to the EIAJ (SC-74A)
TC1070
(SOT-23A-5*)
TOP VIEW
1
3
5
4
2
SHDN
ADJ
GND
V
OUT
V
IN
TC1070
2
50mA ADJUSTABLE CMOS
LDO WITH SHUTDOWN
PRELIMINARY INFORMATION
TC1070-01
6/13/97
ELECTRICAL CHARACTERISTICS:
V
IN
= V
OUT
+ 1V, I
L
= 0.1mA, C
L
= 3.3
F, SHDN > V
IH
, T
A
= 25
C, unless other-
wise specified. BOLDFACE type specifications apply for junction temperatures of
40
C to +125
C.
Symbol
Parameter
Test Conditions
Min
Typ
Max
Units
V
IN
Input Operating Voltage
--
--
6.5
V
I
OUTMAX
Maximum Output Current
50
--
--
mA
V
OUT
Output Voltage
V
REF
V
OUT
(V
IN
0.05) V
R
2.5%
V
R
0.5%
V
R
+ 2.5%
V
I
L
= 0
(Note 1)
V
REF
Reference Voltage
--
1.23
--
V
V
REF
/
T
V
REF
Temperature Coefficient
Note 2
--
40
--
ppm/
C
V
OUT
/
V
IN
Line Regulation
(V
R
+ 1V) < V
IN
< 6V
--
0.05
--
%/V
V
OUT
/V
OUT
Load Regulation
I
L
= 0.1mA to I
OUTMAX
--
0.5
--
%
(Note 3)
V
IN
V
OUT
Dropout Voltage (Note 4)
I
L
= 0.1mA
--
5
--
mV
I
L
= 20mA
65
I
L
= 50mA
95
(Note 4)
I
GND
Ground Pin Current
I
L
= I
OUTMAX,
(Note 5)
--
0
--
A
I
IN
Supply Current
SHDN = V
IH
, I
L
= 0
--
50
--
A
I
INSD
Shutdown Supply Current
SHDN = 0V
--
--
0.05
A
PSRR
Power Supply Rejection Ratio
F
RE
1kHz
--
64
--
dB
I
OUTSC
Output Short Circuit Current
V
OUT
= 0V
--
200
450
mA
V
OUT
/
P
D
Thermal Regulation
Note 6
--
0.04
--
%/W
T
SD
Thermal Shutdown Die Temperature
--
160
--
C
T
SD
Thermal Shutdown Hysteresis
--
10
--
C
eN
Output Noise
I
L
= I
OUTMAX
--
260
--
nV/
Hz
470pF from Bypass to GND
SHDN Input
V
IH
SHDN Input High Threshold
V
IN
= 2.5V to 6.5V
45
--
--
%V
IN
V
IL
SHDN Input Low Threshold
V
IN
= 2.5V to 6.5V
--
--
15
%V
IN
ABSOLUTE MAXIMUM RATINGS*
Input Voltage ................................................................. 7V
Output Voltage .................................. ( 0.3) to (V
IN
+ 0.3)
Power Dissipation .................... Internally Limited (Note 7)
Operating Temperature .................... 40
C < T
J
< 125
C
Storage Temperature ............................ 65
C to +150
C
Maximum Voltage on Any Pin ........... V
IN
+ 0.3V to 0.3V
Lead Temperature (Soldering, 10 Sec.) ................ +260
C
*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 in the operational sections of the specifications is not
implied. Exposure to absolute maximum rating conditions for extended
periods may affect device reliability.
TC1070
3
PRELIMINARY INFORMATION
TC1070-01
6/13/97
50mA ADJUSTABLE CMOS
LDO WITH SHUTDOWN
ELECTRICAL CHARACTERISTICS:
V
IN
= V
OUT
+ 1V, I
L
= 0.1mA, C
L
= 3.3
F, SHDN > V
IH
, T
A
= 25
C, unless otherwise noted.
Symbol
Parameter
Test Conditions
Min
Typ
Max
Units
ADJ Input
I
ADJ
Adjust Input Leakage Current
--
50
--
pA
NOTES: 1. V
R
is the regulator output voltage setting.
2. TC V
OUT
= (V
OUTMAX
V
OUTMIN
)
x 10
6
V
OUT
x
T
3. Regulation is measured at a constant junction temperature using low duty cycle pulse testing. Load regulation is tested over a load
range from 0.1mA to the maximum specified output current. Changes in output voltage due to heating effects are covered by the
thermal regulation specification.
4. Dropout voltage is defined as the input to output differential at which the output voltage drops 2% below its nominal value.
5. Ground pin current is the regulator pass transistor gate current. The total current drawn from the input supply is the sum of the load
current, ground current and supply current (i.e. I
IN
= I
SUPPLY
+ I
GND
+ I
LOAD
).
6. Thermal Regulation is defined as the change in output voltage at a time T after a change in power dissipation is applied, excluding load
or line regulation effects. Specifications are for a current pulse equal to I
LMAX
at V
IN
= 6V for T = 10msec.
7. The maximum allowable power dissipation is a function of ambient temperature, the maximum allowable junction temperature and the
thermal resistance from junction-to-air (i.e. T
A
, T
J
, q
JA
). Exceeding the maximum allowable power dissipation causes the device to
initiate thermal shutdown. Please see
Thermal Considerations section of this data sheet for more details.
Pin No.
1
V
IN
Unregulated supply input.
2
GND
Ground terminal.
3
SHDN
Shutdown control input. The regulator is fully enabled when a logic high is applied to this
input. The regulator enters shutdown when a logic low is applied to this input. During
shutdown, output voltage falls to zero and supply current is reduced to 0.05 microamp
(typical).
4
ADJ
Output voltage adjust terminal. Output voltage setting is programmed with a resistor divider
from V
OUT
to this input. A capacitor may also be added to this input to resuce output noise
(See Text).
5
V
OUT
Regulated voltage output.
PIN DESCRIPTION
(SOT-23A-5)
Symbol
Description
TC1070
4
50mA ADJUSTABLE CMOS
LDO WITH SHUTDOWN
PRELIMINARY INFORMATION
TC1070-01
6/13/97
Output Capacitor
A 1
F (min) capacitor from V
OUT
to ground is recom-
mended. The output capacitor should have an effective
series resistance of 5
or less, and a resonant frequency
above 1MHz. A 1
F capacitor should be connected from V
IN
to GND if there is more than 10 inches of wire between the
regulator and the AC filter capacitor, or if a battery is used as
the power source. Aluminum electrolytic or tantalum capaci-
tor types can be used. (Since many aluminum electrolytic
capacitors freeze at approximately 30
C, solid tantalums
are recommended for applications operating below 25
C.)
When operating from sources other than batteries, supply-
noise rejection and transient response can be improved by
increasing the value of the input and output capacitors and
employing passive filtering techniques.
Thermal Considerations
Thermal Shutdown
Integrated thermal protection circuitry shuts the regula-
tor off when die temperature exceeds 160
C. The regulator
remains off until the die temperature drops to approximately
150
C.
Power Dissipation
The amount of power the regulator dissipates is prima-
rily a function of input and output voltage, and output current.
The following equation is used to calculate worst case
actual power dissipation:
P
D
(V
INMAX
V
OUTMIN
)I
LOADMAX
Where:
P
D
= Worst case actual power dissipation
V
INMAX
= Maximum voltage on V
IN
V
OUTMIN
= Minimum regulator output voltage
I
LOADMAX
= Maximum output (load) current
Equation 2.
The maximum
allowable power dissipation (Equation 2)
is a function of the maximum ambient temperature (T
AMAX
),
the maximum allowable die temperature (125
C) and the
thermal resistance from junction-to-air (
JA
). SOT-23A-5
packag has a
JA
of approximately
220
C/Watt when
mounted on a single layer FR4 dielectric copper clad PC
board.
P
D MAX
= (T
JMAX
T
JMAX)
JA
Where all terms are previously defined.
Equation 3.
DETAILED DESCRIPTION
The TC1070 is a precision fixed output voltage regula-
tor. (If a fixed version is desired, please see the TC1014 or
TC1015 data sheets.) Unlike the bipolar regulators, the
TC1070 supply current does not increase with load current.
In addition, V
OUT
remains stable and within regulation at
very low load currents (an important consideration in RTC
and CMOS RAM battery back-up applications).
Figure 1 shows a typical application circuit. The regula-
tor is enabled any time the shutdown input (SHDN) is at or
above V
IH
, and shutdown (disabled) when SHDN is at or
below V
IL
. SHDN may be controlled by a CMOS logic gate,
or I/O port of a microcontroller. If the SHDN input is not
required, it should be connected directly to the input supply.
While in shutdown, supply current decreases to 0.05
A
(typical) and V
OUT
falls to zero volts.
Adjust Input
The output voltage setting is determined by the values
of R1 and R2 (Figure 1). The ohmic values of these resistors
should be between 470K and 3M to minimize bleeder
current.
The output voltage setting is calculated using the follow-
ing equation.
V
OUT
= V
REF
x
[
R1 + 1
]
R2
Equation 1.
The voltage adjustment range of the TC1070 is from
V
REF
to (V
IN
0.05V). If so desired, a small capacitor (100pF
to 0.01
F) may be added to the ADJ input to further reduce
output noise.
Figure 1. 2.45 Battery-Operated Supply
C2
1
F
C3
100pF
0.01
F
(Optional)
Shutdown Control
(from Power Control Logic)
TC1070
V
IN
1
2
3
4
R2
2.2M
R1
2.2M
+2.45V
5
V
OUT
ADJ
SHDN
GND
3.0V
BATTERY
C1
1
F
TC1070
5
PRELIMINARY INFORMATION
TC1070-01
6/13/97
50mA ADJUSTABLE CMOS
LDO WITH SHUTDOWN
Equation 2 can be used in conjunction with Equation 3
to ensure regulator thermal operation is within limits. For
example:
Given:
V
INMAX
= 3.0V
10%
V
OUTMIN
= 2.7V
0.5V
I
LOAD
= 40mA
T
AMAX
= 55
C
Find:
1. Actual power dissipation
2. Maximum allowable dissipation
Actual power dissipation:
P
D
(V
INMAX
V
OUTMIN
)I
LOADMAX
= [(3.0 x 1.05) (2.7 x .995)]40 x 10
3
= 18.5mW
Maximum allowable power dissipation:
P
DMAX
= (T
JMAX
T
AMAX
)
JA
= (125 55)
220
= 318mW
In this example, the TC1070 dissipates a maximum of
only 60mW; far below the allowable limit of 318mW. In a
similar manner, Equation 2 and Equation 3 can be used to
calculate maximum current and/or input voltage limits.
Layout Considerations
The primary path of heat conduction out of the package
is via the package leads. Therefore, layouts having a ground
plane, wide traces at the pads, and wide power supply bus
lines combine to lower
JA
and therefore increase the
maximum allowable power dissipation limit.
TC1070
6
50mA ADJUSTABLE CMOS
LDO WITH SHUTDOWN
PRELIMINARY INFORMATION
TC1070-01
6/13/97
Printed in the U.S.A.
SOT-23A-5*
PACKAGE DIMENSIONS
Dimensions: inches (mm)
.071 (1.80)
.059 (1.50)
.122 (3.10)
.098 (2.50)
.020 (0.50)
.012 (0.30)
.037 (0.95)
REFERENCE
.122 (3.10)
.106 (2.70)
.057 (1.45)
.035 (0.90)
.006 (0.15)
.000 (0.00)
.022 (0.55)
.008 (0.20)
10
MAX.
.010 (0.25)
.004 (0.09)
SOT-23A-5
&
= part number code + temperature range and voltage
TC1070 (V)
Code
Adjustable
BA
represents year and quarter code
represents lot ID number
NOTE: *SOT-23A-5 is equivalent to the EIAJ (SC-74A)
Sales Offices
TelCom Semiconductor
1300 Terra Bella Avenue
P.O. Box 7267
Mountain View, CA 94039-7267
TEL: 415-968-9241
FAX: 415-967-1590
E-Mail: liter@c2smtp.telcom-semi.com
TelCom Semiconductor H.K. Ltd.
10 Sam Chuk Street, 6/F
San Po Kong
Kowloon
Hong Kong
TEL: 852-2324-0122
FAX: 852-2354-9957
TelCom Semiconductor
Austin Product Center
9101 Burnet Rd. Suite 214
Austin, TX 78758
TEL: 512-873-7100
FAX: 512-873-8236 TelCom
TC1071
1
PRELIMINARY INFORMATION
TC1071-01
6/13/97
100mA ADJUSTABLE CMOS
LDO WITH SHUTDOWN
TC1071
FEATURES
s
Zero Ground Current for Longer Battery Life!
s
Adjustable Output Voltage
s
Very Low Dropout Voltage
s
Guaranteed 100mA Output
s
Power-Saving Shutdown Mode
s
Over-Current and Over-Temperature Protection
s
Space-Saving SOT-23A-5 Package
s
Pin Compatible with LP2980 and MIC5205 Regulators
APPLICATIONS
s
Battery Operated Systems
s
Portable Computers
s
Medical Instruments
s
Instrumentation
s
Cellular / GSM / PHS Phones
s
Linear Post-Regulator for SMPS
s
Pagers
100mA ADJUSTABLE CMOS LDO WITH SHUTDOWN
TYPICAL APPLICATION
TelCom Semiconductor reserves the right to make changes in the circuitry and specifications ot its devices.
GENERAL DESCRIPTION
The TC1071 is an adjustable LDO designed to super-
cede a variety of older (bipolar) voltage regulators. De-
signed specifically for battery-operated systems, the
TC1070's CMOS construction eliminates wasted ground
current, significantly extending battery life. Total supply
current is typically 50
A at full load (
20 to 60 times lower
than in bipolar regulators!).
TC1071 key features include ultra low noise operation
very low dropout voltage (typically 200mV at full load) and
internal feed-forward compensation for fast response to
step changes in load. Supply current is reduced to less than
1
A when the shutdown input is low. The TC1071 incorpo-
rates both over-temperature and over-current protection.
Output voltage is programmed with a simple resistor divider
from V
OUT
to ADJ.
The TC1071 is stable with an output capacitor of only
1
F and has a maximum output current of 100mA. For
higher output versions, please see the TC1174
(I
OUT
= 300mA) data sheet.
C1
1
F
Shutdown Control
(from Power Control Logic)
TC1071
V
IN
1
2
3
4
R2
R1
5
V
IN
V
OUT
ADJ
V
OUT
= V
REF
x
[
R2 + 1
]
R1
SHDN
GND
V
OUT
PIN CONFIGURATION
ORDERING INFORMATION
Output
Junction
Part No.
Voltage **(V) Package
Temp. Range
TC1071VCT
Adjustable
SOT-23A-5* 40
C to +125
C
NOTE: *SOT-23A-5 is equivalent to the EIAJ (SC-74A)
**Other output voltages available. Please contact TelCom
Semiconductor for details
NOTE: *SOT-23A-5 is equivalent to the EIAJ (SC-74A)
TC1071
(SOT-23A-5*)
TOP VIEW
1
3
5
4
2
SHDN
ADJ
GND
V
OUT
V
IN
TC1071
2
100mA ADJUSTABLE CMOS
LDO WITH SHUTDOWN
PRELIMINARY INFORMATION
TC1071-01
6/13/97
ELECTRICAL CHARACTERISTICS:
V
IN
= V
OUT
+ 1V, I
L
= 0.1mA, C
L
= 3.3
F, SHDN > V
IH
, T
A
= 25
C, unless other-
wise specified.BOLDFACE type specifications apply for junction temperatures of
40
C to +125
C.
Symbol
Parameter
Test Conditions
Min
Typ
Max
Units
V
IN
Input Operating Voltage
--
--
6.5
V
I
OUTMAX
Maximum Output Current
100
--
--
mA
V
OUT
Output Voltage
V
REF
V
OUT
(V
IN
0.05) V
R
2.5%
V
R
0.5%
V
R
+ 2.5%
V
I
L
= 0
(Note 1)
V
REF
Reference Voltage
--
1.23
--
V
V
REF
/
T
V
REF
Temperature Coefficient
Note 2
--
40
--
V
OUT
/
V
IN
Line Regulation
(V
R
+ 1V) < V
IN
< 6V
--
0.05
--
%/V
V
OUT
/V
OUT
Load Regulation
I
L
= 0.1mA to I
OUTMAX
--
0.5
--
%
(Note 3)
V
IN
V
OUT
Dropout Voltage (Note 4)
I
L
= 0.1mA
--
20
--
mV
I
L
= 20mA
70
I
L
= 50mA
93
I
L
= 100mA
112
(Note 4)
I
GND
Ground Pin Current
I
L
= I
OUTMAX,
(Note 5)
--
0
--
A
I
IN
Supply Current
SHDN = V
IH
, I
L
= 0
--
50
--
A
I
INSD
Shutdown Supply Current
SHDN = 0V
--
--
0.05
A
PSRR
Power Supply Rejection Ratio
F
RE
1kHz
--
64
--
dB
I
OUTSC
Output Short Circuit Current
V
OUT
= 0V
--
300
450
mA
V
OUT
/
P
D
Thermal Regulation
Note 6
--
0.04
--
%/W
eN
Output Noise
I
L
= I
OUTMAX
--
260
--
nV/
Hz
470pF from Bypass to GND
SHDN Input
V
IH
SHDN Input High Threshold
V
IN
= 2.5V to 6.5V
45
--
--
%V
IN
V
IL
SHDN Input Low Threshold
V
IN
= 2.5V to 6.5V
--
--
15
%V
IN
ABSOLUTE MAXIMUM RATINGS*
Input Voltage ................................................................. 7V
Output Voltage .................................. ( 0.3) to (V
IN
+ 0.3)
Power Dissipation .................... Internally Limited (Note 7)
Operating Temperature .................... 40
C < T
J
< 125
C
Storage Temperature ............................ 65
C to +150
C
Maximum Voltage on Any Pin ........... V
IN
+ 0.3V to 0.3V
Lead Temperature (Soldering, 10 Sec.) ................ +260
C
*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 in the operational sections of the specifications is not
implied. Exposure to absolute maximum rating conditions for extended
periods may affect device reliability.
TC1071
3
PRELIMINARY INFORMATION
TC1071-01
6/13/97
100mA ADJUSTABLE CMOS
LDO WITH SHUTDOWN
ELECTRICAL CHARACTERISTICS:
V
IN
= V
OUT
+ 1V, I
L
= 0.1mA, C
L
= 3.3
F, SHDN > V
IH
, T
A
= 25
C, unless otherwise noted.
Symbol
Parameter
Test Conditions
Min
Typ
Max
Units
ADJ Input
I
ADJ
Adjust Input Leakage Current
--
50
--
pA
NOTES: 1. V
R
is the regulator output voltage setting.
2. TC V
OUT
= (V
OUTMAX
V
OUTMIN
)
x 10
6
V
OUT
x
T
3. Regulation is measured at a constant junction temperature using low duty cycle pulse testing. Load regulation is tested over a load
range from 0.1mA to the maximum specified output current. Changes in output voltage due to heating effects are covered by the
thermal regulation specification.
4. Dropout voltage is defined as the input to output differential at which the output voltage drops 2% below its nominal value.
5. Ground pin current is the regulator pass transistor gate current. The total current drawn from the input supply is the sum of the load
current, ground current and supply current (i.e. I
IN
= I
SUPPLY
+ I
GND
+ I
LOAD
).
6. Thermal Regulation is defined as the change in output voltage at a time T after a change in power dissipation is applied, excluding load
or line regulation effects. Specifications are for a current pulse equal to I
LMAX
at V
IN
= 6V for T = 10msec.
7. The maximum allowable power dissipation is a function of ambient temperature, the maximum allowable junction temperature and the
thermal resistance from junction-to-air (i.e. T
A
, T
J
, q
JA
). Exceeding the maximum allowable power dissipation causes the device to
initiate thermal shutdown. Please see
Thermal Considerations section of this data sheet for more details.
Pin No.
(SOT-23A-5)
Symbol
Description
1
V
IN
Unregulated supply input.
2
GND
Ground terminal.
3
SHDN
Shutdown control input. The regulator is fully enabled when a logic high is applied to this
input. The regulator enters shutdown when a logic low is applied to this input. During
shutdown, output voltage falls to zero and supply current is reduced to 0.05 microamp
(typical).
4
ADJ
Output voltage adjust terminal. Output voltage setting is programmed with a resistor divider
from V
OUT
to this input. A capacitor may also be added to this input to resuce output noise
(See Text).
5
V
OUT
Regulated voltage output.
PIN DESCRIPTION
TC1071
4
100mA ADJUSTABLE CMOS
LDO WITH SHUTDOWN
PRELIMINARY INFORMATION
TC1071-01
6/13/97
Output Capacitor
A 1
F (min) capacitor from V
OUT
to ground is recom-
mended. The output capacitor should have an effective
series resistance of 5
or less, and a resonant frequency
above 1MHz. A 1
F capacitor should be connected from V
IN
to GND if there is more than 10 inches of wire between the
regulator and the AC filter capacitor, or if a battery is used as
the power source. Aluminum electrolytic or tantalum capaci-
tor types can be used. (Since many aluminum electrolytic
capacitors freeze at approximately 30
C, solid tantalums
are recommended for applications operating below 25
C.)
When operating from sources other than batteries, supply-
noise rejection and transient response can be improved by
increasing the value of the input and output capacitors and
employing passive filtering techniques.
Thermal Considerations
Thermal Shutdown
Integrated thermal protection circuitry shuts the regula-
tor off when die temperature exceeds 160
C. The regulator
remains off until the die temperature drops to approximately
150
C.
Power Dissipation
The amount of power the regulator dissipates is prima-
rily a function of input and output voltage, and output current.
The following equation is used to calculate worst case
actual power dissipation:
P
D
(V
INMAX
V
OUTMIN
)I
LOADMAX
Where:
P
D
= Worst case actual power dissipation
V
INMAX
= Maximum voltage on V
IN
V
OUTMIN
= Minimum regulator output voltage
I
LOADMAX
= Maximum output (load) current
Equation 2.
The maximum
allowable power dissipation (Equation 3)
is a function of the maximum ambient temperature (T
AMAX
),
the maximum allowable die temperature (125
C) and the
thermal resistance from junction-to-air (
JA
). SOT-23A-5
package has a
JA
of approximately
220
C/Watt when
mounted on a single layer FR4 dielectric copper clad PC
board.
P
D MAX
= (T
JMAX
T
AMAX)
JA
Where all terms are previously defined.
Equation 3.
DETAILED DESCRIPTION
The TC1071 is a precision fixed output voltage regula-
tor. (If a fixed version is desired, please see the TC1014 or
TC1015 data sheets.) Unlike the bipolar regulators, the
TC1071 supply current does not increase with load current.
In addition, V
OUT
remains stable and within regulation at
very low load currents (an important consideration in RTC
and CMOS RAM battery back-up applications).
Figure 1 shows a typical application circuit. The regula-
tor is enabled any time the shutdown input (SHDN) is at or
above V
IH
, and shutdown (disabled) when SHDN is at or
below V
IL
. SHDN may be controlled by a CMOS logic gate,
or I/O port of a microcontroller. If the SHDN input is not
required, it should be connected directly to the input supply.
While in shutdown, supply current decreases to 0.05
A
(typical) and V
OUT
falls to zero volts.
Adjust Input
The output voltage setting is determined by the values
of R1 and R2 (Figure 1). The ohmic values of these resistors
should be between 470K and 3M to minimize bleeder
current.
The output voltage setting is calculated using the follow-
ing equation.
V
OUT
= V
REF
x
[
R1 + 1
]
R2
Equation 1.
The voltage adjustment range of the TC1071 is from
V
REF
to (V
IN
0.05V). If so desired, a small capacitor (100pF
to 0.01
F) may be added to the ADJ input to further reduce
output noise.
Figure 1. 2.45 Battery-Operated Supply
C2
1
F
Shutdown Control
(from Power Control Logic)
TC1071
V
IN
1
2
3
4
R2
2.2M
R1
2.2M
+2.45V
5
V
OUT
ADJ
SHDN
GND
3.0V
BATTERY
C1
1
F
TC1071
5
PRELIMINARY INFORMATION
TC1071-01
6/13/97
100mA ADJUSTABLE CMOS
LDO WITH SHUTDOWN
Equation 2 can be used in conjunction with Equation 3
to ensure regulator thermal operation is within limits. For
example:
Given:
V
INMAX
= 3.0V
10%
V
OUTMIN
= 2.7V
0.5V
I
LOAD
= 98mA
T
AMAX
= 55
C
Find:
1. Actual power dissipation
2. Maximum allowable dissipation
Actual power dissipation:
P
D
(V
INMAX
V
OUTMIN
)I
LOADMAX
= [(3.0 x 1.1) (2.7 x .995)]40 x 10
3
= 60mW
Maximum allowable power dissipation:
P
DMAX
= (T
JMAX
T
AMAX
)
JA
= (125 55)
220
= 318mW
In this example, the TC1071 dissipates a maximum of
only 60mW; far below the allowable limit of 318mW. In a
similar manner, Equation 1 and Equation 2 can be used to
calculate maximum current and/or input voltage limits. For
example, the maximum allowable V
IN
is found by substitut-
ing the maximum allowable power dissipation of 318mW
into Equation 1, from which V
INMAX
= 5.9V.
Layout Considerations
The primary path of heat conduction out of the package
is via the package leads. Therefore, layouts having a ground
plane, wide traces at the pads, and wide power supply bus
lines combine to lower
JA
and therefore increase the
maximum allowable power dissipation limit.
TC1071
6
100mA ADJUSTABLE CMOS
LDO WITH SHUTDOWN
PRELIMINARY INFORMATION
TC1071-01
6/13/97
Sales Offices
TelCom Semiconductor
1300 Terra Bella Avenue
P.O. Box 7267
Mountain View, CA 94039-7267
TEL: 415-968-9241
FAX: 415-967-1590
E-Mail: liter@c2smtp.telcom-semi.com
Printed in the U.S.A.
TelCom Semiconductor H.K. Ltd.
10 Sam Chuk Street, 6/F
San Po Kong
Kowloon
Hong Kong
TEL: 852-2324-0122
FAX: 852-2354-9957
TelCom Semiconductor
Austin Product Center
9101 Burnet Rd. Suite 214
Austin, TX 78758
TEL: 512-873-7100
FAX: 512-873-8236 TelCom
SOT-23A-5*
PACKAGE DIMENSIONS
Dimensions: inches (mm)
.071 (1.80)
.059 (1.50)
.122 (3.10)
.098 (2.50)
.020 (0.50)
.012 (0.30)
.037 (0.95)
REFERENCE
.122 (3.10)
.106 (2.70)
.057 (1.45)
.035 (0.90)
.006 (0.15)
.000 (0.00)
.022 (0.55)
.008 (0.20)
10
MAX.
.010 (0.25)
.004 (0.09)
SOT-23A-5
&
= part number code + temperature range and voltage
TC1071 (V)
Code
Adjustable
BB
represents year and quarter code
represents lot ID number
NOTE: *SOT-23A-5 is equivalent to the EIAJ (SC-74A)
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