NCV8141 D

NCV8141
5.0 V, 500 mA Linear
Regulator with ENABLE,
RESET, and Watchdog
The NCV8141 is a linear regulator suited for microprocessor
applications in automotive environments.
This ON Semiconductor part provides the power for the
microprocessors along with many of the control functions needed in
today’s computer based systems. Incorporating all of these features
saves both cost, and board space.
The NCV8141 provides a low sleep mode current as compared to
the CS8141. Consult your local sales representative for a low sleep
mode current version of the CS8140.
Features
•
•
•
•
•
•
•
•
•
•
•
5.0 V ± 3.0%, 500 mA Output Voltage
Lower Quiescent Current
Improved Filtering for /RESET Functionality
mP Compatible Control Functions
♦ Watchdog
♦ RESET
♦ ENABLE
Low Dropout Voltage (1.25 V @ 500 mA)
Low Quiescent Current (7.0 mA @ 500 mA)
Low Noise, Low Drift
Low Current SLEEP Mode 50 mA (max)
Fault Protection
♦ Thermal Shutdown
♦ Short Circuit
♦ 60 V Peak Transient Voltage
These are Pb−Free Devices
NCV Prefix for Automotive and Other Applications Requiring Site
and Control Changes
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MARKING
DIAGRAM
NC
V8141
AWLYWWG
D2PAK−7
DPS SUFFIX
CASE 936AB
1
1
A
WL
Y
WW
G
= Assembly Location
= Wafer Lot
= Year
= Work Week
= Pb−Free Package
PIN CONNECTIONS
Tab = GND
Pin
1. VIN
2. ENABLE
3. RESET
4. GND
5. Delay
6. WDI
7. VOUT
1
ORDERING INFORMATION
Package
Shipping†
NCV8141D2TG
D2PAK
(Pb−Free)
50 Units/Rail
NCV8141D2TR4G
D2PAK
(Pb−Free)
750/Tape & Reel
Device
†For information on tape and reel specifications,
including part orientation and tape sizes, please
refer to our Tape and Reel Packaging Specifications
Brochure, BRD8011/D.
© Semiconductor Components Industries, LLC, 2009
October, 2009 − Rev. 13
1
Publication Order Number:
NCV8141/D
NCV8141
VIN
Reference & Bias
Overvoltage
Overtemperature
Regulation
ENABLE
Control Logic
ENABLE
RESET
Delay
WDI
VOUT
Short Circuit
Undervoltage
GND
Watchdog
Sense
RESET
Delay
Figure 1. Block Diagram
PIN FUNCTION DESCRIPTION
Pin
Symbol
Function
1
VIN
2
ENABLE
3
RESET
4
GND
Ground Connection.
5
Delay
Timing capacitor for Watchdog and RESET functions.
6
WDI
CMOS compatible input lead. The Watchdog function monitors the falling edge of the incoming digital
pulse train. The signal is usually generated by the system microprocessor.
7
VOUT
Regulated output voltage, 5.0 V (typ).
Supply voltage to IC, usually direct from the battery.
CMOS compatible logical input. VOUT is disabled when ENABLE is LOW and WDI is invalid.
CMOS compatible output lead. RESET goes low whenever VOUT drops 4.5% below its typical value for
more than 2.0 ms or WDI signal falls below the watchdog threshold frequency.
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NCV8141
MAXIMUM RATINGS
Rating
Value
Unit
−0.5 to 26
V
Peak Transient Voltage (46 V Load Dump @ 14 V VBAT)
60
V
Electrostatic Discharge (Human Body Model)
4.0
kV
−0.3 to 7.0
V
Internally Limited
−
Junction Temperature Range (TJ)
−40 to +150
°C
Storage Temperature Range
−65 to +150
°C
ENABLE
−0.3 to VIN
V
1.5
10−50†
°C/W
°C/W
225 peak (Note 2)
°C
Input Operating Range
WDI Input Signal Range
Internal Power Dissipation
Package Thermal Resistance, D2PAK 7−Pin
Junction−to−Case, RqJC
Junction−to−Ambient, RqJA
Lead Temperature Soldering:
Reflow (SMD styles only) (Note 1)
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
†Depending on thermal properties of substrate RqJA = RqJC + RqCA.
1. 60 seconds max above 183°C.
2. −5.0°C/+0°C allowable conditions.
ELECTRICAL CHARACTERISTICS (7.0 ≤ VIN ≤ 26 V, 5.0 mA ≤ IOUT ≤ 500 mA, −40°C ≤ TJ ≤ 150°C, −40°C ≤ TA ≤ 125°C, unless otherwise
noted.) (Note 3)
Test Conditions
Min
Typ
Max
Unit
7.0 V ≤ VIN ≤ 26 V, 5.0 mA < IOUT < 500 mA
4.85
5.0
5.15
V
IOUT = 500 mA
−
1.25
1.50
V
Line Regulation
IOUT = 50 mA, 7.0 V ≤ VIN ≤ 26 V,
−
5.0
25
mV
Load Regulation
VIN = 14 V, 50 mA ≤ IOUT ≤ 500 mA
−
5.0
80
mV
500 mA DC and 10 mA AC,
100 Hz ≤ f ≤ 10 kHz
−
200
−
mW
0 ≤ IOUT ≤ 500 mA, 7.0 V ≤ VIN ≤ 26 V
IOUT = 0 mA, VIN = 13 V, ENABLE = 0 V
−
−
7.0
25
15
50
mA
mA
7.0 V ≤ VIN ≤ 17 V, IOUT = 250 mA,
f = 120 Hz
60
75
−
dB
VIN = 7.0 V, VOUT = 4.5 V
600
1200
2000
mA
Guaranteed by Design
150
180
−
°C
VOUT < 1.0 V
30
34
38
V
VOUT ≥ 0.5 V, (VOUT(ON))
VOUT < 0.5 V, (VOUT(OFF))
−
3.5
4.05
3.95
4.50
−
V
V
ENABLE = 5.0 V
ENABLE = 0 V
−
−1.0
35
0
75
1.0
mA
mA
(HIGH − LOW)
−
80
−
mV
Characteristic
Output Stage (VOUT)
Output Voltage, VOUT
Dropout Voltage (VIN − VOUT)
Output Impedance, ROUT
Quiescent Current, (IQ)
Active Mode
Sleep Mode
Ripple Rejection
Current Limit
Thermal Shutdown
Overvoltage Shutdown
ENABLE
Threshold
HIGH
LOW
Input Current
HIGH
LOW
Threshold Hysteresis
3. To observe safe operating junction temperatures, low duty cycle pulse testing is used in tests where applicable.
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NCV8141
ELECTRICAL CHARACTERISTICS (continued) (7.0 ≤ VIN ≤ 26 V, 5.0 mA ≤ IOUT ≤ 500 mA, −40°C ≤ TJ ≤ 150°C, −40°C ≤ TA ≤
125°C, unless otherwise noted.) (Note 4)
Characteristic
Test Conditions
Min
Typ
Max
Unit
Threshold HIGH VR(HI)
VOUT Increasing
4.65
4.90
VOUT − 0.05
V
Threshold LOW VR(LOW)
VOUT Decreasing
4.50
4.70
4.90
V
Threshold Hysteresis (VRH)
(HIGH − LOW)
150
200
250
mV
RESET Output Leakage
RESET = HIGH
VOUT ≥ VR(HI)
−
−
25
mA
Output Voltage Low (VL(LOW))
1.0 V ≤ VOUT ≤ VR(LOW), RP = 2.7 kW (Note 5)
−
0.1
0.4
V
Output Voltage Low (VRpeak)
VOUT, Power up, Power down
−
0.6
1.0
V
Delay Time tPOR
CDELAY = 0.1 mF
30
47.5
65
ms
Delay Time tWDI(RESET)
CDELAY = 0.1 mF
0.5
1.0
1.5
ms
Input Voltage High
−
2.0
−
−
V
Input Voltage Low
−
−
−
0.8
V
WDI ≤ VOUT
−
0
10
mA
CDELAY = 0.1 mF
64
77
105
Hz
RESET
Watchdog
Input Current
Threshold Frequency fWDI
4. To observe safe operating junction temperatures, low duty cycle pulse testing is used in tests where applicable.
5. RP is connected to RESET and VOUT.
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NCV8141
TYPICAL PERFORMANCE CHARACTERISTICS
1.4
1.2
1.0
−40°C
0.8
+25°C
0.6
+125°C
0.4
0.9
0.8
Iout = 100 mA
0.7
Iout = 10 mA
0.6
0
50
0.5
−40
100 150 200 250 300 350 400 450 500
OUTPUT CURRENT (mA)
Figure 2. Dropout Voltage vs. Output Current over
Temperature
1000
125°C
Unstable Region
25°C
1000
0
20
40
60
80
TEMPERATURE (°C)
Unstable Region
−40°C
10
10
ESR (W)
100
Stable Region
1
−20
100
120
Figure 3. Dropout Voltage vs. Temperature
100
10 mF
0.1 mF
Stable Region
1
T = 25°C
0.1
0.01
0.1
Cvout = 1 mF to 10 mF
0
10
20
30
40
50
OUTPUT CURRENT (mA)
60
0.01
70
Figure 4. Output Stability
55
54
NOTE: At 125°C an additional area of instability occurs
(0.1 mF only) for loads less than 5 mA and low ESR.
0
10
50
20
30
40
OUTPUT CURRENT (mA)
Cdelay = 0.1 mF
52
51
50
49
48
47
−40 −20
60
70
Figure 5. Output Stability with Capacitor Change
53
TIME (ms)
ESR (W)
Iout = 350 mA
1.0
0.2
0
Iout = 500 mA
1.1
DROPOUT VOLTAGE (V)
DROPOUT VOLTAGE (V)
1.2
0
20 40 60 80 100 120 140 160
TEMPERATURE (°C)
Figure 6. Delay Time
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NCV8141
DEFINITION OF TERMS
Dropout Voltage: The input−output voltage differential
at which the circuit ceases to regulate against further
reduction in input voltage. Measured when the output
voltage has dropped 100 mV from the nominal value
obtained at 14 V input, dropout voltage is dependent upon
load current and junction temperature.
Input Voltage: The DC voltage applied to the input
terminals with respect to ground.
Line Regulation: The change in output voltage for a
change in the input voltage. The measurement is made under
conditions of low dissipation or by using pulse techniques
such that the average chip temperature is not significantly
affected.
Load Regulation: The change in output voltage for a
change in load current at constant chip temperature.
Quiescent Current: The part of the positive input current
that does not contribute to the positive load current. The
regulator ground lead current.
Ripple Rejection: The ratio of the peak−to−peak input
ripple voltage to the peak−to−peak output ripple voltage.
Current Limit: Peak current that can be delivered to the
output.
CIRCUIT DESCRIPTION
VOLTAGE REFERENCE AND OUTPUT CIRCUITRY
The NCV8141 is a 5.0 V Watchdog Regulator with
protection circuitry and three logic control functions that
allow a microprocessor to control its own power supply. The
NCV8141 is designed for use in automotive, switch mode
power supply post regulator, and battery powered systems.
Basic regulator performance characteristics include a low
noise, low drift, 5.0 V ±3.0% precision output voltage with
low dropout voltage (1.25 V @ IOUT = 500 mA) and low
quiescent current (7.0 mA @ IOUT = 500 mA). On board
short circuit, thermal, and overvoltage protection make it
possible to use this regulator in particularly harsh operating
environments.
The Watchdog logic function monitors an input signal
(WDI) from the microprocessor or other signal source.
When the signal frequency goes below the externally
programmable limit, a RESET signal is generated (RESET).
Proper operation has been verified at a frequency up to 100
kHz. No abnormal RESET signals will occur with
frequencies lower than 100 kHz and the maximum
Threshold Frequency (96 Hz). An external capacitor
(CDELAY) programs the watchdog frequency limit as well as
the power on reset (POR) and RESET delay.
The RESET function is activated by any of three
conditions: the watchdog signal moves outside of its preset
limits; the output voltage drops out of regulation by more
than 4.5%; or the IC is in its power up sequence. The RESET
signal is independent of VIN and reliable down to VOUT =
1.0 V.
In conjunction with the Watchdog, the ENABLE
function controls the regulator’s power consumption. The
NCV8141’s output stage and its attendant circuitry are
enabled by setting the ENABLE lead high. The regulator
goes into sleep mode when the ENABLE lead goes low and
the watchdog signal moves outside its preset limit. This
unique combination of control functions in the NCV8141
gives the microprocessor control over its own power down
sequence: i.e. it gives the microprocessor the flexibility to
perform housekeeping functions before it powers down.
Precision Voltage Reference
The regulated output voltage depends on the precision band
gap voltage reference in the IC. By adding an error amplifier
into the feedback loop, the output voltage is maintained within
±3.0% over temperature and supply variation.
Output Stage
The composite PNP−NPN output structure (Figure 7)
provides 500 mA (min) of output current while maintaining
a low drop out voltage (1.25 V) and drawing little quiescent
current (7.0 mA).
VIN
VOUT
Figure 7. Composite Output Stage of the NCV8141
The NPN pass device prevents deep saturation of the
output stage which in turn improves the IC’s efficiency by
preventing excess current from being used and dissipated by
the IC.
Output Stage Protection
The output stage is protected against overvoltage, short
circuit and thermal runaway conditions (Figure 8).
If the input voltage rises above 30 V (e.g. load dump), the
output shuts down. This response protects the internal
circuitry and enables the IC to survive unexpected voltage
transients.
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NCV8141
ENABLE circuitry in the IC remains powered up, drawing
a quiescent current of less than 50 mA.
The Watchdog monitors the frequency of an incoming
WDI signal. If the signal falls below the WDI limit, a
frequency programmable pulse train is generated at the
RESET lead (Figure 9) until the correct Watchdog input
signal reappears at the lead (ENABLE = HIGH).
The threshold limit of the watchdog function is set by the
value of CDELAY. The limit is determined according to the
following equation for the NCV8141:
Using an emitter sense scheme, the amount of current
through the NPN pass transistor is monitored. Feedback
circuitry insures that the output current never exceeds a
preset limit.
> 30 V
VIN
VOUT
tWDI + (1.3
Load
Dump
Short
Circuit
105)CDELAY or
The capacitor CDELAY also determines the frequency of
the RESET signal and the POWER−ON−RESET (POR)
delay period.
IO
Thermal
Shutdown
RESET Function
Figure 8. Typical Circuit Waveforms for Output
Stage Protection
The RESET function is activated when the Watchdog
frequency signal is below the watchdog threshold
(Figure 9), when the regulator is in its power up state
(Figure 10) or when VOUT drops below VOUT −4.5% for
more than 2.0 ms (Figure 11)
If the Watchdog signal falls outside of the preset voltage
or below the frequency threshold, a frequency
programmable pulse train is generated at the RESET lead
(Figure 9) until the correct Watchdog input signal reappears
at the lead. The duration of the RESET pulse is determined
by CDELAY according to the following equation:
Should the junction temperature of the power device
exceed 180°C (typ), the power transistor is turned off.
Thermal shutdown is an effective means to prevent die
overheating since the power transistor is the principle heat
source in the IC.
REGULATOR CONTROL FUNCTIONS
The NCV8141 differs from all other linear regulators in its
unique combination of control features.
tWDI(RESET) + (1.0
Watchdog and ENABLE Function
VOUT is controlled by the logic functions ENABLE and
Watchdog (Table 1).
RESET CIRCUIT WAVEFORMS WITH DELAYS
INDICATED
If an undervoltage condition exists, the voltage on the
RESET lead goes low and the delay capacitor, CDELAY, is
discharged. RESET remains low until output is in
regulation, the voltage on CDELAY exceeds the upper
threshold and the Watchdog input signal is valid (Figures 10
and 11). The delay after the output is in regulation is:
Table 1. VOUT as a Function of ENABLE and Watchdog
VOUT (V)
WDI
ENABLE
Slow
Normal
High
Low
H
5
5
5
5
L
0
5
0
0
104)CDELAY
tPOR(typ) + (4.75
105)CDELAY
The RESET delay circuit is also programmed with the
external cap CDELAY.
The output of the reset circuit is an open collector NPN.
RESET is operational down to VOUT = 1.0 V. Both RESET
and its delay are governed by comparators with hysteresis to
avoid undesirable oscillations.
As long as ENABLE is high or ENABLE is low and the
Watchdog signal is normal, VOUT will be at 5.0 V (typ). If
ENABLE is low and the frequency of the Watchdog input
goes below the threshold frequency, the output transistor
turns off and the IC goes into SLEEP mode. Only the
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NCV8141
Batt
VIN
VOUT When Watchdog is Held
High and ENABLE = HIGH
Batt
ENABLE
WDI 0 V
RESET 0 V
VOUT 0 V
POR Normal Operation
WDI held High
Batt
VIN
VOUT When Watchdog is Held Low
and ENABLE = HIGH
Batt
ENABLE
WDI 0 V
RESET 0 V
VOUT 0 V
POR Normal Operation
WDI held Low
Batt
VIN
VOUT When Watchdog is too Slow
and ENABLE = HIGH
Batt
ENABLE
WDI 0 V
RESET 0 V
VOUT 0 V
POR Normal Operation
Slow WDI signal
Batt
Batt
VIN
WDI Held High After a Normal Period
of Operation; ENABLE = LOW
ENABLE
WDI 0 V
RESET 0 V
VOUT 0 V
POR Normal Operation
WDI Sleep Mode
high
POR Normal Operation
Batt
VIN
WDI Held Low or is too Slow after
a Normal Period of Operation;
ENABLE = LOW
Batt
ENABLE
WDI 0 V
RESET 0 V
VOUT 0 V
POR
Normal
Operation
WDI
low
Sleep Mode
POR Normal Operation
Figure 9. Timing Diagrams for Watchdog and ENABLE Functions
VOUT
VOUT
VOUT −4.5%
VR(HI)
VR(LO)
< 6.0 ms
≥ 6.0 ms
RESET
RESET
VR(LO)
VR(PEAK)
5.0 V
tPOR
tPOR
Figure 10. Power RESET and Power Down
Figure 11. Undervoltage Triggered RESET
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NCV8141
APPLICATION NOTES
With a capacitor tolerance of ±10%:
NCV8141 DESIGN EXAMPLE
The NCV8141 with its unique integration of linear
regulator and control features: RESET, ENABLE and
WATCHDOG, provides a single IC solution for a
microprocessor power supply. The reset delay, reset
duration and watchdog frequency limit are all determined by
a single capacitor. For a particular microprocessor the
overriding requirement is usually the reset delay (also
known as power on reset). The capacitor is chosen to meet
this requirement and the reset duration and watchdog
frequency follow.
The reset delay is given by:
tWDI + (1.3
tWDI + (1.3
105
0.63)
Hz
ms
0.9
CDELAY
PASS
7
141
13
76
ENERGY CONSERVATION AND SMART FEATURES
Energy conservation is another benefit of using a
regulator with integrated microprocessor control features.
Using the NCV8141 as indicated in Figure 13, the
microprocessor can control its own power down sequence.
The momentary contact switch quickly charges C1 through
R1.
When the voltage across C1 reaches 3.95 V ( the enable
threshold), the output switches on and VOUT rises to 5.0 V.
After a delay period determined by CDelay, a frequency
programmable reset pulse train is generated at the reset
output. The pulse train continues until the correct watchdog
signal appears at the WDI lead. C1 is now left to discharge
through the input impedance of the enable lead
(approximately 150 kW) and the enable signal disappears.
The output voltage remains at 5.0 V as long as the NCV8141
continues to receive the correct watchdog signal.
The microprocessor can power itself down by terminating
its watchdog signal. When the microprocessor finishes its
housekeeping or power down software routine, it stops
sending a watchdog signal. In response, the regulator
generates a reset signal and goes into a sleep mode where
VOUT drops to 0 V, shutting down the microprocessor.
Closest standard value is 0.82 mF.
Minimum and maximum delays using 0.82 mF are 220 ms
and 586 ms.
The duration of the reset pulse is given by:
CDELAY
This has a tolerance of ±50% due to the IC, and ±10% due
to the capacitor.
The duration of the reset pulse ranges from 3.69 ms to
13.5 ms.
The watchdog signal can be expressed as a frequency or
time. From a programmers point of view, time is more useful
since they must ensure that a watchdog signal is issued
consistently several times per second.
The watchdog time is given by:
tWDI + (1.3
0.8
Figure 12. WDI Signal for CDelay = 0.82 mF using
NCV8141
0.9
CDELAY(min) + 0.743 mF
104)
CDelay
The software must be written so that a watchdog signal
arrives at least every 76 ms.
t
(min)
CDELAY(min) + POR
2.69 105
TWDI(RESET)(typ) + (1.0
105)
FAIL
CDELAY
1.1
tWDI + 76 ms (min)
Assume that the reset delay must be 200 ms minimum.
From the NCV8141 data sheet the reset delay has a $37%
tolerance due to the regulator.
Assume the capacitor tolerance is $10%.
tPOR(min) + (4.75
1.2
tWDI + 141 ms (max)
105)CDELAY
tPOR(typ) + (4.75
105)
105)CDELAY
There is a tolerance of ±20% due to the NCV8141.
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NCV8141
9.0 V
VOUT
VIN
NCV8141
Switch
R1
110 K
RESET
C1
0.1 mF
WDI
ENABLE
CDELAY
GND
C2
0.1 mF
VCC
10 mF
2.7 kW
Microprocessor
RESET
WATCHDOG PORT
Figure 13. Application Diagram for NCV8141. The NCV8141 Provides a 5.0 V Tightly Regulated
Supply and Control Function to the Microprocessor. In this Application, the Microprocessor
Controls its own Power Down Sequence (see text).
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NCV8141
Battery
VOUT
VIN
C1 *
0.1 mF
(optional)
Ignition
C2 *
10 mF*
2.7 kW
NCV8141
ENABLE
RESET
RESET
DELAY
0.1 mF
GND
VCC
WATCHDOG
PORT
WDI
R***
Microprocessor
*C1 is required if regulator is located far from the power source filter.
**C2 is required for stability.
***R ≤ 80 kW.
Figure 14. Application Diagram
Step 4: Maintain the worst case load conditions set in
Step 3 and vary the input voltage until the oscillations
increase. This point represents the worst case input voltage
conditions.
Step 5: If the capacitor is adequate, repeat Steps 3 and 4
with the next smaller valued capacitor. A smaller capacitor
will usually cost less and occupy less board space. If the
output oscillates within the range of expected operating
conditions, repeat Steps 3 and 4 with the next larger standard
capacitor value.
Step 6: Test the load transient response by switching in
various loads at several frequencies to simulate its real
working environment. Vary the ESR to reduce ringing.
Step 7: Increase the temperature to the highest specified
operating temperature. Vary the load current as instructed in
Step 5 to test for any oscillations.
Once the minimum capacitor value with the maximum
ESR is found, a safety factor should be added to allow for the
tolerance of the capacitor and any variations in regulator
performance. Most good quality aluminum electrolytic
capacitors have a tolerance of ± 20% so the minimum value
found should be increased by at least 50% to allow for this
tolerance plus the variation which will occur at low
temperatures. The ESR of the capacitor should be less than
50% of the maximum allowable ESR found in Step 3 above.
STABILITY CONSIDERATIONS
The output or compensation capacitor C2 in Figure 14
helps determine three main characteristics of a linear
regulator: startup delay, load transient response and loop
stability.
The capacitor value and type should be based on cost,
availability, size and temperature constraints. An aluminum
electrolytic capacitor is the least expensive solution, but, if
the circuit operates at low temperatures (−25°C to −40°C),
both the value and ESR of the capacitor will vary
considerably. The capacitor manufacturers data sheet
usually provides this information.
The value for the output capacitor C2 shown in Figure 14
should work for most applications, however it is not
necessarily the optimized solution.
To determine an acceptable value for C2 for a particular
application, start with a tantalum capacitor of the
recommended value and work towards a less expensive
alternative part.
Step 1: Place the completed circuit with a tantalum
capacitor of the recommended value in an environmental
chamber at the lowest specified operating temperature and
monitor the outputs with an oscilloscope. A decade box
connected in series with the capacitor will simulate the
higher ESR of an aluminum capacitor. Leave the decade box
outside the chamber, the small resistance added by the
longer leads is negligible.
Step 2: With the input voltage at its maximum value,
increase the load current slowly from zero to full load while
observing the output for any oscillations. If no oscillations
are observed, the capacitor is large enough to ensure a stable
design under steady state conditions.
Step 3: Increase the ESR of the capacitor from zero using
the decade box and vary the load current until oscillations
appear. Record the values of load current and ESR that cause
the greatest oscillation. This represents the worst case load
conditions for the regulator at low temperature.
CALCULATING POWER DISSIPATION IN A SINGLE
OUTPUT LINEAR REGULATOR
The maximum power dissipation for a single output
regulator (Figure 15) is:
PD(max) + NJVIN(max) * VOUT(min)NjIOUT(max) ) VIN(max)IQ
where:
VIN(max) is the maximum input voltage,
VOUT(min) is the minimum output voltage,
IOUT(max) is the maximum output current for the
application, and
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(1)
NCV8141
In some cases, none of the packages will be sufficient to
dissipate the heat generated by the IC, and an external
heatsink will be required.
IQ is the quiescent current the regulator consumes at
IOUT(max).
IIN
VIN
SMART
REGULATOR®
IOUT
HEATSINKS
VOUT
A heatsink effectively increases the surface area of the
package to improve the flow of heat away from the IC and
into the surrounding air.
Each material in the heat flow path between the IC and the
outside environment will have a thermal resistance. Like
series electrical resistances, these resistances are summed to
determine the value of RqJA.
Control
Features
IQ
RqJA + RqJC ) RqCS ) RqSA
Figure 15. Single Output Regulator With Key
Performance Parameters Labeled
where:
RqJC = the junction−to−case thermal resistance,
RqCS = the case−to−heatsink thermal resistance, and
RqSA = the heatsink−to−ambient thermal resistance.
RqJC appears in the package section of the data sheet. Like
RqJA, it too is a function of package type. RqCS and RqSA are
functions of the package type, heatsink and the interface
between them. These values appear in heatsink data sheets
of heatsink manufacturers.
Once the value of PD(max) is known, the maximum
permissible value of RqJA can be calculated:
RqJA +
150° C * TA
PD
(3)
(2)
The value of RqJA can then be compared with those in the
package section of the data sheet. Those packages with
RqJA’s less than the calculated value in Equation 2 will keep
the die temperature below 150°C.
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NCV8141
PACKAGE DIMENSIONS
D2PAK−7 (SHORT LEAD)
CASE 936AB−01
ISSUE B
A
E
L1
B
A
0.10
A
E/2
NOTES:
1. DIMENSIONING AND TOLERANCING PER ASME
Y14.5M, 1994.
2. CONTROLLING DIMENSION: INCHES.
3. DIMENSIONS D AND E DO NOT INCLUDE MOLD
FLASH AND GATE PROTRUSIONS. MOLD FLASH
AND GATE PROTRUSIONS NOT TO EXCEED
0.005 MAXIMUM PER SIDE. THESE DIMENSIONS
TO BE MEASURED AT DATUM H.
4. THERMAL PAD CONTOUR OPTIONAL WITHIN
DIMENSIONS E, L1, D1, AND E1. DIMENSIONS
D1 AND E1 ESTABLISH A MINIMUM MOUNTING
SURFACE FOR THE THERMAL PAD.
SEATING
PLANE
M
B A
M
E1
c2
D1
D
7X
H
e
b
0.13
M
B A
DETAIL C
VIEW A−A
c
A
M
B
H
SEATING
PLANE
A1
RECOMMENDED
SOLDERING FOOTPRINT*
0.424
DIM
A
A1
b
c
c2
D
D1
E
E1
e
H
L
L1
L3
M
INCHES
MIN
MAX
0.170
0.180
0.000
0.010
0.026
0.036
0.017
0.026
0.045
0.055
0.325
0.368
0.270
−−−
0.380
0.420
0.245
−−−
0.050 BSC
0.539
0.579
0.058
0.078
−−−
0.066
0.010 BSC
0°
8°
MILLIMETERS
MIN
MAX
4.32
4.57
0.00
0.25
0.66
0.91
0.43
0.66
1.14
1.40
8.25
9.53
6.86
−−−
9.65
10.67
6.22
−−−
1.27 BSC
13.69
14.71
1.47
1.98
−−−
1.68
0.25 BSC
0°
8°
L
M
0.310
L3
GAUGE
PLANE
DETAIL C
0.584
0.136
7X
0.040
0.050
PITCH
DIMENSIONS: MILLIMETERS
*For additional information on our Pb−Free strategy and soldering
details, please download the ON Semiconductor Soldering and
Mounting Techniques Reference Manual, SOLDERRM/D.
SMART REGULATOR is a registered trademark of Semiconductor Components Industries, LLC (SCILLC).
ON Semiconductor and
are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice
to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability
arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages.
“Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All
operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC does not convey any license under its patent rights
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