MICROSEMI LX8942

LX8942
®
TM
Low Dropout Dual Regulator
P RODUCTION D ATA S HEET
KEY FEATURES
DESCRIPTION
The high current regulator has over
voltage shutdown to protect both the internal
circuitry and the load during line transients,
such as load dump (60V). In addition, the
high current regulator design also has builtin protection for short circuit and thermal
overload. During these fault conditions of
the primary output, the standby regulator
will continue to power its load.
The LX8942 is the 8.2 volt, ±5% version
of a family of dual regulators with a standby
output voltage of 5V. Other high-current
outputs programmed for 5V and 12V
regulation are available in the SG29055,
SG29125 devices. They are designed to
function over the full automotive ambient
temperature range of -40°C to 85°C.
ƒ 2% Internally Trimmed Output
ƒ Two regulated outputs
ƒ Output current in excess of
1000mA
ƒ Low quiescent current standby
regulator
ƒ Drop-out Voltage, Input-output
differential <0.6V at 0.5A
ƒ Reverse battery protection
ƒ 60V load dump protection
ƒ -50V reverse transient protection
ƒ Short circuit protection
ƒ Internal thermal overload
protection
ƒ ON/OFF switch for high current
output
ƒ Surface Mount TO-252
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The Microsemi LX8942 is a dual
8.2V/5V positive voltage regulator. One
output is a high current (up to 1000mA)
regulator that can be turned on or off by a
high impedance low current TTL
compatible switch. The second or standby
output remains on regardless. The on/off
switch not only shuts off the high current
output but actually puts the IC in a
micropower
mode,
achieving
low
quiescent
current.
This
unique
characteristic coupled with an extremely
low dropout, (0.55V for output current of
10mA) makes the LX8942 well suited for
power systems that require standby
memory. The LX8942 includes other
features which were originally designed
for automotive applications. These include
protection
from
reverse
battery
installations, double battery jumps and
load dump (transients).
APPLICATIONS
ƒ Automotive electronics for
controls, entertainment and
safety functions
ƒ Continuous operation systems
IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com
PRODUCT HIGHLIGHT
* Required close to regulator package.
** Required for stability. May be increased without bound.
Capacitor must be rated to operate at the minimum
temperature expected for the regulator system.
Input Voltage
(VIN)
C1*
0.1µF
1
Output Voltage (VOUT1)
(8.2V, 1000mA)
2
Over Voltage
Thermal
Shutdown
C2 **
47µF
+
-
ON/OFF Switch (for
output voltage only)
Regulator
Bias
4
1.23V
Reference
5V Standby
Regulator
LX8942
5
Standby Output (VSB)
(5V, 60mA)
C3**
100µF
3
LX8942
Ground
PACKAGE ORDER INFO
TJ (°C)
DT
Plastic TO-252
5-Pin
RoHS Compliant / Pb-free
-40 to 85
LX8942IDT
Note: Available in Tape & Reel. Append the letters “TR” to the part number. (i.e. LX8942IDT-TR)
Copyright © 2005
Rev. 1.2, 2006-01-20
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
LX8942
®
TM
Low Dropout Dual Regulator
P RODUCTION D ATA S HEET
ABSOLUTE MAXIMUM RATINGS
PACKAGE PIN OUT
GROUND
STANDBY OUTPUT (VSB)
ON/OFF SWITCH
GROUND
OUTPUT VOLTAGE (VOUT1)
INPUT VOLTAGE (VIN)
DT PACKAGE
(Top View)
Note: Exceeding these ratings could cause damage to the device. All voltages are with respect to
Ground. Currents are positive into, negative out of specified terminal.
RoHS / Pb-free 100% matte Tin Lead Finish
Note: The heat sink tab is the Ground
Connection for this package.
THERMAL DATA
DT
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Input Voltage (VIN) Operating .......................................................................................26V
Input Voltage (VIN) Over Voltage Transient.................................................... -15V to 60V
ON/OFF Switch ................................................................................................-0.3V to VIN
Operating Ambient Temperature Range ..................................................... -40°C to +85°C
Storage Temperature Range (TSTG)..............................................................-65°C to 150°C
Maximum Operating Junction Temperature (TJ) ....................................................... 150°C
Plastic TO-252 5-Pin
THERMAL RESISTANCE-JUNCTION TO CASE, θJC
9°C/W
80°C/W
THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA
Junction Temperature Calculation: TJ = TA + (PD x θJA).
The θJA numbers are guidelines for the thermal performance of the device/pc-board system. All of the
above assume no ambient airflow.
FUNCTIONAL PIN DESCRIPTION
Name
VIN
Description
Input Voltage Supply.
VOUT1
+8.2V Output Voltage at up to 1000mA.
GND
Regulator Ground.
ON/OFF
VSB
TTL Logic level input control for turning ON and OFF the high current VOUT1 regulator.
+5V Standby Output Voltage at up to 60mA.
RECOMMENDED OPERATING CONDITIONS
Range over which the device is functional.
Symbol
Input Voltage
ON/OFF Threshold Voltage Low Level, (VOUT1 is OFF)
ON/OFF Threshold Voltage High level, (VOUT1 is ON)
Load Current VOUT1 (with adequate heatsinking)
Maximum Line Transient (Load Dump) VSB < 6V
Input Capacitor (VIN to GND)
Reverse Polarity D.C. Input Voltage (VIN) (VOUT1 > -0.6V, 16Ω Load)
Reverse Polarity Transient Input Voltage (VIN) (1% Duty Cycle, T <
100ms, VOUT1 > -9V, 16Ω Load)
Output Capacitor (VOUT1 to GND & VSB to GND)
Output Capacitor ESR Value
VIN
VIL
VIH
Copyright © 2005
Rev. 1.2, 2006-01-20
Min
9
2
5
LX8942
Typ
Max
26
0.8
-15
V
V
V
mA
V
µF
V
-50
V
5.0
µF
Ω
1000
60
0.1
10
0.5
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Units
PACKAGE DATA
Parameter
Page 2
LX8942
®
TM
Low Dropout Dual Regulator
P RODUCTION D ATA S HEET
ELECTRICAL CHARACTERISTICS
Parameter
`
Symbol
Test Conditions
Min
Max
Units
VOLTAGE OUTPUT (VOUT1) SECTION
Output Voltage (NOTE 1)
VOUT1
Line Regulation
Load Regulation
Output Impedance
Quiescent Current
Output Noise Voltage
9V < VIN < 26V, IO1 < 1000mA
9V < VIN < 16V, IO1 = 5mA
9V < VIN < 26V, IO1 = 5mA
5mA < IO1 < 1000mA
500mADC and 10mARMS, 100Hz – 10kHz
IO1 < 10mA, No Load on Standby
IO1 = 500mA, No Load on Standby
IO1 = 750mA, No Load on Standby
7.6
10Hz – 100kHz
8.0
4
10
10
200
2
40
90
8.4
25
50
50
100
100
Long Term Stability
20
Ripple Rejection
FO1 = 120Hz
IO1 = 500mA
IO1 = 1000mA
Dropout Voltage
Current Limit
Maximum Operational Input
Voltage
Maximum Line Transient
ON / OFF Switch
ON / OFF Switch
`
LX8942
Typ
VIN
Double Battery
VIN
IIH
IIL
VO1 < 9V
IO1 = 10mA, Pin 4 = 2.4V
IO1 = 10mA, Pin 4 = 0.4V
VSB
6V < VIN < 26V, ISB < 60mA
6V < VIN < 26V
1mA < ISB < 35mA
1mA < ISB < 60mA
1mADC and 1mARMS, 100Hz – 10kHz
ISB < 10mA, VOUT1 OFF
10Hz – 100kHz
1.0
66
0.45
0.7
1.8
26.5
31
60
70
0.60
1.2
V
mV
mV
mV
mΩ
mA
mA
mA
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Unless otherwise specified, the following specifications apply over the operating ambient temperature 0°C ≤ TA ≤ 70°C except where
otherwise noted and the following test conditions: TA = 25°C, VIN = 14V, IO1 = 50mA for VOUT1 and 10mA for VSB and are for DC
characteristics only. Low duty cycle pulse testing techniques are used which maintains junction and case temperatures equal to the
ambient temperature.
µVRMS
mV /
1000hr
dB
V
V
A
V
10
-10
V
µA
µA
STANDBY OUTPUT (VSB) SECTION
Output Voltage (Note 1)
Line Regulation
Load Regulation
Output Impedance
Quiescent Current
Output Noise Voltage
4.75
Long Term Stability
5.0
4
10
25
1
1.2
300
5.25
50
25
50
3
20
Ripple Rejection
Dropout Voltage
Current Limit
Maximum Line Transient
FSB = 120Hz
ISB < 60mA
VIN
4.75V < VSB < 6V
60
60
66
0.55
100
70
0.70
V
mV
mV
mV
Ω
mA
µVRMS
mV /
1000hr
dB
V
mA
V
Copyright © 2005
Rev. 1.2, 2006-01-20
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
ELECTRICALS
Note 1: The Temperature Extremes are Guaranteed but not 100% Production Tested.
Page 3
LX8942
®
TM
Low Dropout Dual Regulator
P RODUCTION D ATA S HEET
TYPICAL CIRCUIT WAVEFORMS
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60V
Load Dump
Double Battery
33V
INPUT VOLTAGE
PIN 1(V)
26V
14V
14V
4V
0V
2V
ON/OFF SWITCH
0.8V
8.2V
OUTPUT
VOLTAGE 2 (V)
8.2V
8.2V
8.2V
8.2V
5V
3.5V
0V
STANDBY
VOLTAGE
PIN 5 (V)
System
Conditions
5V
3.7V
TURN
ON
LOAD
DUMP
LOW
VIN
LINE
NOISE,
ETC.
VOUT
SHORT
CIRCUIT
THERMAL
SHUTDOWN
TURN
OFF
APPLICATION
Copyright © 2005
Rev. 1.2, 2006-01-20
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 4
LX8942
TM
®
Low Dropout Dual Regulator
P RODUCTION D ATA S HEET
APPLICATION NOTE
STANDBY OUTPUT
The LX8942 differs from most fixed voltage regulators
in that it is equipped with two regulator outputs instead of
one. The additional output is intended for use in systems
requiring standby memory circuits. While the high current
regulator output can be controlled with the ON/OFF pin
described below, the standby remains on under all
conditions as long as sufficient input voltage is applied to
the IC. Thus, memory and other circuits powered by this
output remain unaffected by positive line transients,
thermal shutdown, etc.
The standby regulator circuit is designed so that the
quiescent current to the IC is very low (<1.5mA) when the
other regulator output is off.
If the standby output is not required it can be disabled.
This is accomplished by connecting a resistor from the
standby output to the supply voltage, thereby also
eliminating the requirement for a more expensive output
capacitor to prevent unwanted oscillations. The resistor
value depends upon the minimum input voltage expected
for a given system. Since the standby output is shunted
with an internal 5.6V zener, the current through the
external resistor should be sufficient to bias internal
resistors up to this point. Approximately 60mA will
suffice, resulting in a 10k external resistor for most
applications (Figure 1).
VIN
RD
10K
APPLICATIONS
EXTERNAL CAPACITORS
To stabilize the outputs and prevent oscillation (perhaps
by many volts) external capacitors are required. The
minimum recommended value for the output capacitors is
47μF for the 8.2V output and 100µF for the 5V output. The
actual size and type will likely vary according to the
particular application, e.g., operating temperature range and
load. Another consideration is the effective series resistance
(ESR) of the capacitor. Capacitor ESR will vary by
manufacturer. Consequently, some evaluation may be
required to determine the minimum value of the output
capacitors. Generally worst case occurs at the maximum
load and minimum ambient temperature.
The size of the output capacitor can be increased to any
value above the minimum. One possible advantage of this
would be to maintain the output voltage during brief
periods of negative input transients.
The output capacitors chosen should be rated for the full
range of ambient temperature over which the circuit will be
exposed and expected to operate. For example, many
aluminum type electrolytic capacitors will freeze at -30°C.
The effective capacitance is reduced to zero in such a
situation. Capacitors rated for -40°C operation must be
used in order to maintain regulator stability at that
temperature. Tantalum capacitors satisfy this requirement.
Standby
Output
LX8942
Part
C3
Figure 1 – Disabling Standby Output to Eliminate C3
Copyright © 2005
Rev. 1.2, 2006-01-20
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
WWW . Microsemi .C OM
The advantages of using a low-dropout regulator such as
the LX8942 are the need for less “headroom” for full
regulation, and the inherent reverse polarity protection
provided by the PNP output device. A typical NPN
regulator design requires an input to output differential of
approximately two volts minimum. This is due to the 2Vbe
+ Vcesat of the NPN Darlington used in the output, coupled
with the voltage drop across the current limit resistor. In
contrast, the “PNP Regulator” uses a single series pass
transistor with its single Vcesat, thus the lower input to
output voltage differential or dropout voltage.
In addition to a low dropout voltage, an important
advantage of the LX8942 series is low quiescent current in
the standby mode. When the high current or primary
regulator is shut off, the regulator enters a micropower
mode. Here all but the most essential circuitry to power the
standby output is deactivated. This allows the lowest
possible quiescent current (typical around 1.2mA), a vital
factor when used in a battery powered system.
In some applications the regulator output voltage is used
not only as a power supply but also as a voltage reference
for control systems. In such cases not just the temperature
stability of the output is important but also the initial
accuracy. The LX8942 fills this need as the internal
bandgap reference is trimmed allowing a typical output
voltage tolerance of ±1%.
Page 5
LX8942
TM
®
Low Dropout Dual Regulator
P RODUCTION D ATA S HEET
APPLICATION NOTE
ON/OFF SWITCH
The ON/OFF pin is a high impedance low current
switch that controls the main output voltage (pin 2). This is
directly compatible with all 5 volt logic families. For use
with open collector logic outputs, a 100Kresistor from this
pin to a 5V supply, such as Pin 5, is required.
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The high current regulated output features fault
protection against over voltage as well as a thermal
shutdown feature. If the input voltage rises above 33V (load
dump), the high current output shuts down automatically.
The internal circuitry is thus protected and the IC is able to
survive higher voltage transients than might otherwise be
expected. The thermal shutdown of the high current output
effectively guards against overheating of the die since this
section of the IC is the principle source of power dissipation
on the chip.
APPLICATIONS
Copyright © 2005
Rev. 1.2, 2006-01-20
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 6
LX8942
®
TM
Low Dropout Dual Regulator
P RODUCTION D ATA S HEET
PACKAGE DIMENSIONS
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DT
5-Pin Plastic TO-252
E
b3
A
c2
L3
D
H
L
e
b2
C
Dim
A
A1
b2
b3
C
c2
D
E
e
H
L
L3
Ø
MILLIMETERS
MIN
MAX
2.18
2.39
0
0.23
0.62
0.78
5.00
5.46
0.45
0.61
0.46
0.89
5.96
6.22
6.35
6.73
1.27 BSC
9.40
10.41
1.08
1.40
0.89
1.27
0.85
1.62
INCHES
MIN
MAX
0.086
0.094
0
0.009
0.024
0.031
0.197
0.215
0.018
0.024
0.018
0.035
0.235
0.245
0.250
0.265
0.050 BSC
0.370
0.410
0.043
0.055
0.035
0.050
0.033
0.064
Note:
1. Dimensions do not include mold flash or protrusions;
these shall not exceed 0.155mm(.006”) on any side.
Lead dimension shall not include solder coverage.
A1
MECHANICALS
Copyright © 2005
Rev. 1.2, 2006-01-20
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 7
LX8942
TM
®
Low Dropout Dual Regulator
P RODUCTION D ATA S HEET
NOTES
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NOTES
PRODUCTION DATA – Information contained in this document is proprietary to
Microsemi and is current as of publication date. This document may not be modified in
any way without the express written consent of Microsemi. Product processing does not
necessarily include testing of all parameters. Microsemi reserves the right to change the
configuration and performance of the product and to discontinue product at any time.
Copyright © 2005
Rev. 1.2, 2006-01-20
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 8