CHERRY CS5210-1GT3

CS5210-1
CS5210-1
10A LDO 3-Pin Adjustable Linear Regulator
Features
Description
The CS5210-1 linear regulator provides 10A at adjustable voltages
from 1.25V to 4.5V. This adjustable
device requires two external resistors to set the output voltage and
provide the minimum load current
for proper regulation.
This regulator is intended for use as
a post regulator and microprocessor
supply. The fast loop response and
low dropout voltage make this regulator ideal for applications where
low voltage operation and good
transient response are important.
■ 1.25V to 4.5V VOUT at 10A
The circuit is designed to operate
with dropout voltages as low as
1.05V at 10A.
■ Dropout Voltage < 1.05V @ 10A
The regulator is protected against
overload conditions with overcurrent and thermal shutdown protection circuitry.
■ Fast Transient Response
The regulator is available in a
TO-220 package.
Applications Diagram
■ 2% Trimmed Reference
■ Thermal Shutdown
■ Current Limit
■ Short Circuit Protection
Package Options
3 Lead TO-220
5.0V
VOUT
VIN
[email protected]
CS5210-1
Adj
124
100mF
0.1mF
200
300mF
Load
1
1. Adjust
2. VOUT
3. VIN
Tab = VOUT
Cherry Semiconductor Corporation
2000 South County Trail, East Greenwich, RI 02818
Tel: (401)885-3600 Fax: (401)885-5786
Email: [email protected]
Web Site: www.cherry-semi.com
Rev. 6/12/97
1
A
¨
Company
CS5210-1
Absolute Maximum Ratings
Input Voltage ............................................................................................................................................................................6V
Operating Ambient Temperature Range.......................................................................................................0¡C ² TA ² 70¡C
Operating Junction Temperature Range.......................................................................................................0¡C ² TJ ² 150¡C
Storage Temperature Range ............................................................................................................................-65¡C to +150¡C
Lead Temperature Soldering
Wave Solder (through hole styles only) .................................................................................10 sec. max, 260¡C peak
ESD Damage Threshold ........................................................................................................................................................2kV
Electrical Characteristics: 0¡C²TA ² 70¡C, 0¡C²TJ ² 150¡C, VAdj = 0V unless otherwise specified.
PARAMETER
TEST CONDITIONS
Reference voltage
VIN=2.75V to 5.5V, IOUT=10mA to 10A
Line Regulation
Load Regulation
Minimum Load Current
(Note 1)
Adjust Pin Current
VIN=2.75V to 5.5V, IOUT=10mA
VIN=2.75V,IOUT=10mA to 10A
VIN=5V, ÆVOUT= +2%
Current Limit
Short Circuit Current
Ripple Rejection
(Note 2)
Thermal Regulation
(Note 2)
Dropout Voltage
(Minimum VIN -VOUT)
(Note 3)
RMS Output Noise
Temperature Stability
Thermal Shutdown
(Note 4)
Thermal Shutdown Hysteresis
(Note 4)
VIN=2.75V,IOUT=10mA
VIN=2.75V,ÆVOUT= -2%
VIN=2.75V,VOUT=0V
VIN=3.25V Avg,
VRipple=1VP-P @120Hz,
IOUT=4A,CAdj=0.1µF, COUT=22µF
30ms Pulse, TA=25¡C
MIN
TYP
MAX
UNIT
1.227
(-2%)
1.253
1.278
(+2%)
.20
.50
10
V
120
µA
A
A
dB
.02
.04
5
10.1
8.0
60
70
12.0
10.0
80
0.002
IOUT=100mA
IOUT=1A
IOUT=2.75A
IOUT=4A
IOUT=10A
Freq=10Hz to 10kHz, TA=25¡C
150
0.92
0.93
0.94
0.95
1.03
0.003
0.5
180
25
%
%
mA
%/W
1.15
1.15
1.15
1.15
1.40
210
V
V
V
V
V
%VOUT
%
¡C
¡C
Note 1: The minimum load current is the minimum current required to maintain regulation. Normally the current in the resistor divider used to set
the output voltage is selected to meet the minimum load current requirement.
Note 2: This parameter is guaranteed by design and is not 100% production tested.
Note 3: Dropout voltage is defined as the minimum input/output voltage differential required to maintain 2% regulation.
Note 4: This parameter is guaranteed by design, but not parametrically tested in production. However, a 100% thermal shutdown functional test is
performed on each part.
2
CS5210-1
Package Pin Description
PACKAGE PIN #
PIN SYMBOL
FUNCTION
3L TO-220
1
Adjust
This pin is connected to the low side of the internally trimmed
2% bandgap reference voltage and carries a bias current of
about 70µA. A resistor divider from Adj to VOUT and from Adj
to ground sets the output voltage. Also, transient response can
be improved by adding a small bypass capacitor from this pin
to ground.
2
VOUT
This pin is connected to the emitter of the power pass transistor
and provides a regulated voltage capable of sourcing 10A of
current.
3
VIN
This is the supply voltage for the regulator. For the device to
regulate, this voltage should be between 1.2V and 1.40V
(depending on the output current) greater than the output
voltage.
Block Diagram
VIN
BIAS
and
TSD
VREF
-
EA
+
IA
+
VOUT
-
Adj
Typical Performance Characteristics
90.00
73.00
85.00
Adjust Pin Current (uA)
ADJUST PIN CURRENT (mA)
I0=10mA
80.00
75.00
70.00
72.80
72.60
72.40
72.20
72.00
71.80
71.60
71.40
71.20
71.00
70.80
70.60
70.40
70.20
70.00
65.00
60.00
0 10 20 30 40 50 60 70 80 90 100 110120130
0.00
TCase (°C)
1.00
2.00 3.00 4.00 5.00 6.00 7.00 8.00
IOUT (A)
Adjust Pin Current vs IOUT
Adjust Pin Current Voltage vs Temperature
3
9.00 10.00
CS5210-1
OUTPUT VOLTAGE DEVIATION (%)
0.100
0.075
OUTPUT VOLTAGE DEVIATION (%)
Typical Performance Characteristics: continued
I0=10mA
VIN=2.75V
0.050
0.025
-0.000
-0.025
-0.050
-0.075
-0.100
-0.125
-0.150
0 10 20 30 40 50 60 70 80 90 100 110120130
0.350
0.300
TCase=25°C
0.250
0.200
0.150
TCase=125°C
0.100
0.050
TCase=0°C
0.000
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.0010.00
OUTPUT CURRENT (A)
TJ (°C)
Reference Voltage vs Temperature
Load Regulation vs Output Current
90.0
1.250
1.000
70.0
VDROPOUT (mV)
Ripple Rejection (dB)
80.0
60.0
50.0
40.00
VIN-VOUT=2V
IOUT=4A
VRIPPLE=1VP-P
COUT=22mF
CADJ=0.1mF
30.0
20.0
0.750
0.500
0.250
0.000
10.0
101
102
103
105
104
0
106
1.0
2.0 3.0
4.0
5.0
6.0 7.0
8.0
9.0
10
Output Current (A)
Frequency (Hz)
Ripple Rejection vs Frequency
VDropout vs IOUT
20.0
1.00
18.0
0.98
Minimum Load Current (mA)
16.0
Output Current (A)
14.0
12.0
10.0
8.0
6.0
4.0
0.96
0.94
TCASE =23˚C
0.92
0.90
TCASE =125˚C
0.88
0.86
0.84
TCASE =0˚C
0.82
2.0
0.80
0.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
50
1.00
5.5
2.00
3.00
VIN-VOUT (V)
VIN-VOUT (V)
Minimum Load Current vs VIN-VOUT
Ilmin vs VIN - VOUT
4
4.00
5.00
specification of 6V for the voltage difference between VIN
and VOUT. However, the IC may be used to regulate voltages in excess of 6V. The main considerations in such a
design are power-up and short circuit capability.
Theory of Operation
The CS5210-1 linear regulator has a composite PNP-NPN
output stage that requires an output capacitor for stability.
A detailed procedure for selecting this capacitor is included in the Stability Considerations section.
In most applications, ramp-up of the power supply to VIN
is fairly slow, typically on the order of several tens of milliseconds, while the regulator responds in less than one
microsecond. In this case, the linear regulator begins
charging the output capacitor as soon as the VIN to VOUT
differential is large enough that the pass transistor conducts current. VOUT is essentially at ground, and VIN is on
the order of several hundred millivolts, so that the pass
transistor is in dropout. As VIN increases, the pass transistor will remain in dropout, and current is passed to the
load until VOUT is in regulation. Further increase in VIN
brings the pass transistor out of dropout. The result is that
the output voltage follows the power supply ramp-up,
staying in dropout until the regulation point is reached. In
this manner, any output voltage may be regulated. There
is no theoretical limit to the regulated voltage as long as
the VIN to VOUT differential of 6V is not exceeded.
Adjustable Operation
Design Guidelines
This LDO adjustable regulator has an output voltage range
of 1.25V to 4.5V. An external resistor divider sets the output voltage as shown in Figure 1. The regulatorÕs voltage
sensing error amplifier maintains a fixed 1.25V reference
between the output pin and the adjust pin.
A resistor divider network R1 and R2 causes a fixed current
to flow to ground. This current creates a voltage across R2
that adds to the 1.25V across R1 and sets the overall output
voltage. The adjust pin current (typically 50µA) also flows
through R2 and adds a small error that should be taken
into account if precise adjustment of VOUT is necessary.
The output voltage is set according to the formula:
However, maximum ratings of the IC will be exceeded in a
short circuit condition. Short circuit conditions will result
in the immediate operation of the pass transistor outside of
its safe operating area. Over-voltage stresses will then
cause destruction of the pass transistor before overcurrent
or thermal shutdown circuitry can become active.
Additional circuitry may be required to clamp VIN to VOUT
differential to less than 6V if failsafe operation is required.
One possible clamp circuit is illustrated below; however,
the design of clamp circuitry must be done on an application by application basis. Care must be taken to ensure the
clamp actually protects the design. Components used in
the clamp design must be able to withstand the short circuit conditions indefinitely while protecting the IC.
R + R2
VOUT = VREF ´ 1
+ R2 ´ IAdj
R1
The term IAdj ´ R2 represents the error added by the adjust
pin current.
R1 is chosen so that the minimum load current is a least
10mA. R1 and R2 should be of the same composition for
best tracking over temperature. The divider resistor
should be placed as close to the IC as possible and connected to the output with a separate metal trace.
VIN
VOUT
CS5210-1
Adj
EXTERNAL SUPPLY
R1
R2
VIN
VOUT
VAdj
Figure 1:
While not required, a bypass capacitor connected between
the adjust pin and ground will improve transient response
and ripple rejection. A 0.1µF tantalum capacitor is recommended for Òfirst cutÓ design. Value and type may be varied to optimize performance vs price.
Figure 2:
The CS5210-1 linear regulator has an absolute maximum
5
CS5210-1
Application Notes: continued
CS5210-1
Application Notes: continued
If the calculated current is greater than or equal to the typical short circuit current valued provided in the specifications, serious thought should be given to include a protection diode.
Stability Considerations
The output compensation capacitor helps determine three
main characteristics of a linear regulator: start-up delay,
load transient response, and loop stability.
The capacitor value and type is based on cost, availability,
size and temperature constraints. A tantalum or aluminum
electrolytic capacitor is best, since a film or ceramic capacitor with almost zero ESR can cause instability. The aluminum electrolytic capacitor is the least expensive solution.
However, when the circuit operates at low temperatures,
both the value and ESR of the capacitor will vary considerably. The capacitor manufacturerÕs data sheet provides this
information.
A 300µF tantalum capacitor will work for most applications, but with high current regulators such as the CS5210
the transient response and stability improve with higher
values of capacitance. The majority of applications for this
regulator involve large changes in load current so the output capacitor must supply the instantaneous load current.
The ESR of the output capacitor causes an immediate drop
in output voltage given by:
CS5210-1
Adj
Figure 3:
ÆV = ÆI ´ ESR.
Current Limit
The internal current limit circuit limits the output current
under excessive load conditions and protects the regulator.
For microprocessor applications it is customary to use an
output capacitor network consisting of several tantalum and
ceramic capacitors in parallel. This reduces the overall ESR
and reduces the instantaneous output voltage drop under
transient load conditions. The output capacitor network
should be as close to the load as possible for the best results.
Short Circuit Protection
The device includes foldback short circuit current limit that
clamps the output current at approximately two amperes
less than its current limit value.
Protection Diodes
When large external capacitors are used with a linear regulator it is sometimes necessary to add protection diodes. If
the input voltage of the regulator gets shorted, the output
capacitor will discharge into the output of the regulator.
The discharge current depends on the value of the capacitor, the output voltage, and the rate at which VIN drops. In
the CS5210-1 regulator, the discharge path is through a
large junction and protection diodes are not usually needed. If the regulator is used with large values of output
capacitance and the input voltage is instantaneously shorted to ground, damage can occur. In this case, a diode connected as shown in Figure 3 is recommended.
A rule of thumb useful in determining if a protection diode
is required is to solve for current
I=
I
C
V
T
VOUT
VIN
Thermal Shutdown
The thermal shutdown circuitry is guaranteed by design to
become activated above a die junction temperature of
150¡C and to shut down the regulator output. This circuitry includes a thermal hysteresis circuit with 25¡C of typical
hysteresis, thereby allowing the regulator to recover from a
thermal fault automatically.
Calculating Power Dissipation and Heat Sink
Requirements
High power regulators such as the CS5210-1 usually operate at high junction temperatures. Therefore, it is important
to calculate the power dissipation and junction temperatures accurately to ensure that an adequate heat sink is
used. Since the package tab is connected to Vout on the
CS5210-1, electrical isolation may be required for some
applications. Also, as with all high power packages, thermal compound in necessary to ensure proper heat flow.
For added safety, this high current LDO includes an internal thermal shutdown circuit.
The thermal characteristics of an IC depend on the following four factors. Junction temperature, ambient temperature, die power dissipation, and the thermal resistance
C ´V
, where
T
is the current flow out of the load capacitance
when VIN is shorted,
is the value of load capacitance
is the output voltage, and
is the time duration required for VIN to transition
from high to being shorted.
6
from the die junction to ambient air. The maximum junction temperature can be determined by:
RQJC is rated @ 1.4¡C/W for the CS5210-1. For a high current regulator such as the CS5210-1 the majority of heat is
generated in the power transistor section. The value for
RQSA depends on the heat sink type, while the RQCS
depends on factors such as package type, heat sink interface (is an insulator and thermal grease used?), and the
contact area between the heat sink and the package. Once
these calculations are complete, the maximum permissible
value of RQJA can be calculated and the proper heat sink
selected. For further discussion on heat sink selection, see
our Cherry application note ÒThermal Management for
Linear Regulators.Ó
TJ(max) = TA(max) + PD(max) ´ RQJA
The maximum ambient temperature and the power dissipation are determined by the design while the maximum
junction temperature and the thermal resistance depend on
the manufacturer and the package type. The maximum
power dissipation for a regulator is:
PD(max) = (VIN(max) -VOUT(min))IOUT(max) + VIN(max) ´ IIN(max)
A heat sink 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 has a
thermal resistance which is measured in degrees per watt.
Like series electrical resistances, these thermal resistances
are summed to determine the total thermal resistance
between the die junction and the surrounding air, RQJA.
This total thermal resistance is comprised of three components. These resistive terms are measured from junction to
case (RQJC), case to heat sink (RQCS), and heat sink to ambient air (RQSA). The equation is:
RQJA = RQJC + RQCS + RQSA
7
CS5210-1
Application Notes: continued
CS5210-1
Package Specification
PACKAGE DIMENSIONS IN mm (INCHES)
PACKAGE THERMAL DATA
Thermal Data
RQJC
RQJA
typ
typ
3L
TO-220
1.4
50
ûC/W
ûC/W
3 Lead TO-220 (T) Straight
4.83 (.190)
4.06 (.160)
10.54 (.415)
9.78 (.385)
3.96 (.156)
3.71 (.146)
2.87 (.113)
2.62 (.103)
6.55 (.258)
5.94 (.234)
1.40 (.055)
1.14 (.045)
14.99 (.590)
14.22 (.560)
1.52 (.060)
1.14 (.045)
14.22 (.560)
13.72 (.540)
6.17 (.243) REF
1.40 (.055)
1.14 (.045)
1.02 (.040)
0.63 (.025)
0.56 (.022)
0.38 (.014)
2.79 (.110)
2.29 (.090)
5.33 (.210)
4.83 (.190)
2.92 (.115)
2.29 (.090)
Ordering Information
Part Number
CS5210-1GT3
Rev. 6/12/97
Cherry Semiconductor Corporation reserves the
right to make changes to the specifications without
notice. Please contact Cherry Semiconductor
Corporation for the latest available information.
Description
3L TO-220 Straight
8
© 1999 Cherry Semiconductor Corporation