CHERRY CS5205A

CS5205A-1
CS5205A-1
5A Adjustable Linear Regulator
Description
The CS5205A-1 linear regulator
provides 5A at an adjustable voltage with an accuracy of ±1%. Two
external resistors are used to set the
output voltage within a 1.25V to
13V range.
The 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.
The circuit is designed to operate
with dropout voltages as low as 1V
Features
depending on the output current
level. The maximum quiescent current is only 10mA at full load.
■ Output Current to 5A
The regulator is fully protected
against overload conditions with
protection circuitry for Safe
Operating Area (SOA), overcurrent
and thermal shutdown.
■ Dropout Voltage
1.15V @ 5A
The CS5205A-1 is pin compatible
with the LT1084 family of linear
regulators but has lower dropout
voltage.
■ Output Trimmed to +/- 1%
■ Fast Transient Response
■ Fault Protection Circuitry
Thermal Shutdown
Overcurrent Protection
Safe Area Protection
The regulator is available in TO-220
and surface mount D2 packages.
Package Options
Block Diagram
3L TO-220
3L D2PAK
Tab (VOUT)
V OUT
V IN
1
1
2
3
Output
Current
Limit
Thermal
Shutdown
-
+
Adj
VOUT
VIN
1
Error
Amplifier
Bandgap
Adj
Cherry Semiconductor Corporation
2000 South County Trail, East Greenwich, RI 02818
Tel: (401)885-3600 Fax: (401)885-5786
Email: info@cherry-semi.com
Web Site: www.cherry-semi.com
Rev. 7/8/97
1
A
¨
Company
CS5205A-1
Absolute Maximum Ratings
Supply Voltage, VCC .....................................................................................................................................................................17V
Operating Temperature Range ..................................................................................................................................-40¡C to 70¡C
Junction Temperature ...............................................................................................................................................................150¡C
Storage Temperature Range .....................................................................................................................................-60¡C to 150¡C
Lead Temperature Soldering
Wave Solder (through hole styles only) ........................................................................................10 sec. max, 260¡C peak
Reflow (SMD styles only) .........................................................................................60 sec. max above 183¡C, 230¡C peak
Electrical Characteristics: CIN = 10µF, COUT = 22µF Tantalum, VIN Ð VOUT=3V, VIN ² 15V, 0¡C ² TA ² 70¡C, TJ ² +150¡C,
unless otherwise specified, Ifull load = 5A.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
1.241
(-1%)
1.254
1.266
(+1%)
V
■ Adjustable Output Voltage
Reference Voltage
(Notes 1 and 2)
VINÐVOUT=1.5V; VAdj = 0V
10mA²IOUT²5A
Line Regulation
1.5V²VINÐVOUT²6V; IOUT=10mA
0.04
0.20
%
Load Regulation
(Notes 1 and 2)
VINÐVOUT=1.5V;
10mA²IOUT²5A
0.08
0.4
%
Dropout Voltage (Note 3)
IOUT=5A; TJ ³ 25¡C
1.15
1.25
V
Current Limit
VINÐVOUT=3V; TJ ³ 25¡C
VINÐVOUT=9V
Minimum Load Current
VINÐVOUT=7V
5.5
Adjust Pin Current
Adjust Pin Current Change
1.5V²VINÐVOUT²4V;
10mA²IOUT²5A
8.5
1.0
A
A
1.2
6
mA
50
100
µA
0.2
5.0
µA
Thermal Regulation
30ms pulse; TA=25¡C
0.003
%W
Ripple Rejection
f=120Hz; CAdj=25µF; IOUT=5A
82
dB
0.5
%
0.003
%VOUT
180
¡C
25
¡C
Temperature Stability
10Hz²f²10kHz; TA=25¡C
RMS Output Noise
Thermal Shutdown
150
Thermal Shutdown Hysteresis
Note 1: Load regulation and output voltage are measured at a constant junction temperature by low duty cycle pulse testing. Changes in output voltage due to thermal gradients or temperature changes must be taken into account separately.
Note 2: Specifications apply for an external Kelvin sense connection at a point on the output pin 1/4Ó from the bottom of the package.
Note 3: Dropout voltage is a measurement of the minimum input/output differential at full load.
Package Pin Description
PACKAGE PIN #
D2PAK
1
2
3
3L TO-220
1
2
3
PIN SYMBOL
Adj
VOUT
VIN
FUNCTION
Adjust pin (low side of the internal reference).
Regulated output voltage (case).
Input voltage.
2
CS5205A-1
Typical Performance Characteristics
0.10
1.20
0.08
Dropout Voltage (V)
1.15
Output Voltage Deviation (%)
1.25
TCASE = 0°C
1.10
1.05
1.00
0.95
TCASE = 125°C
0.90
TCASE = 25°C
0.85
0.80
0.75
0.04
0.02
0.00
-0.02
-0.04
-0.06
-0.08
-0.10
0.70
-0.12
0
1
2
3
Output Current (A)
4
5
0
20
10
30
40
50
60
70
80
90 100 110 120 130
TJ (°C)
Reference Voltage vs. Temperature
Dropout Voltage vs. Output Current
2.500
0.200
Minimum Load Current (mA)
0.175
Output Voltage Deviation (%)
0.06
0.150
0.125
0.100
TCASE = 25°C
0.075
TCASE = 125°C
0.050
2.175
1.850
TCASE = 0°C
1.525
1.200
TCASE = 125°C
0.875
TCASE = 25°C
0.025
TCASE = 0°C
0.550
0.000
0
1
2
3
4
1
5
2
Output Current (A)
Load Regulation vs. Output Current
Minimum Load Current
100.0
Ripple Rejection (dB)
90.0
80.0
70.0
60.0
50.0
TCASE = 25°C
IOUT = 5A
(VIN Ð VOUT) = 3V
VRIPPLE = 1.6VPP
CAdj = 25mF
40.0
30.0
20.0
10.0
0.0
101
102
103
104
105
Frequency (Hz)
Ripple Rejection vs. Frequency
3
3
4
5
VIN – VOUT (V)
6
7
8
9
CS5205A-1
Applications Information
tor 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 manufacturers data sheet provides this information.
A 22µF tantalum capacitor will work for most applications,
but with high current regulators such as the CS5205A-1 the
transient response and stability improve with higher values of capacitor. 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:
The CS5205A-1 linear regulator provides an adjustable
voltage at currents up to 5A. The regulator is protected
against short circuit, and include thermal shutdown and
safe area protection (SOA) circuitry. The SOA protection
circuitry decreases the maximum available output current
as the input-output differential voltage increases.
The CS5205A-1 has a composite PNP-NPN output transistor and requires an output capacitor for stability. A
detailed procedure for selecting this capacitor is included
in the Stability Considerations section.
Adjustable Operation
The adjustable regulator (CS5205A-1) has an output voltage range of 1.25V to 13V. An external resistor divider sets
the output voltage as shown in Figure 1. The regulator
maintains a fixed 1.25V (typical) 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:
VOUT
(
ÆV = ÆI ´ ESR
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 load transient conditions. The output capacitor network should be as close as possible to the load for the best
results.
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 CS5205A-1 linear 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 Figure2 is recommended.
)
= VREF ´ R1 + R2 + IAdj ´ R2
R1
The term IAdj ´ R2 represents the error added by the adjust
pin current.
R1 is chosen so that the minimum load current is at least
10mA. R1 and R2 should be the same type, e.g. metal film
for best tracking over temperature. The adjust pin is
bypassed to improve the transient response and ripple
rejection of the regulator.
VIN
VOUT
VIN
C1
IN4002
VOUT
VIN
CS5205A-1
R1
C1
C2
VOUT
VIN
VREF
(optional)
VOUT
CS5205A-1
Adj
R1
C2
Adj
IAdj
CAdj
R2
CAdj
Figure 1. Resistor divider scheme for the adjustable version.
R2
Figure 2. Protection diode scheme for adjustable output regulator.
Stability Considerations
Output Voltage Sensing
The output or 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 capaci-
Since the CS5205A-1 is a three terminal regulator, it is not
possible to provide true remote load sensing. Load regulation is limited by the resistance of the conductors connecting the regulator to the load.
4
Best load regulation occurs when R1 is connected directly
to the output pin of the regulator as shown in Figure 3. If
R1 is connected to the load, RC is multiplied by the divider
ratio and the effective resistance between the regulator and
the load becomes
(
RC ´ R1 + R2
R1
The maximum power dissipation for a regulator is:
PD(max)={VIN(max)ÐVOUT(min)}IOUT(max)+VIN(max)IQ
(2)
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
RC = conductor parasitic resistance
IQ is the maximum quiescent current at IOUT(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.
RC
VOUT
VIN
Each material in the heat flow path between the IC and the
outside environment has a thermal resistance. Like series
electrical resistances, these resistances are summed to
determine RQJA, the total thermal resistance between the
junction and the surrounding air.
conductor parasitic
resistance
CS5205A-1
RLOAD
R1
1. Thermal Resistance of the junction to case, RQJC (¡C/W)
Adj
2. Thermal Resistance of the case to Heat Sink, RQCS (¡C/W)
R2
3. Thermal Resistance of the Heat Sink to the ambient air,
RQSA (¡C/W)
These are connected by the equation:
RQJA = RQJC + RQCS + RQSA
Figure 3. Grounding scheme for the adjustable output regulator to minimize parasitics.
The value for RQJA is calculated using equation (3) and the
result can be substituted in equation (1).
The value for RQJC is normally quoted as a single figure for
a given package type based on an average die size. For a
high current regulator such as the CS5205A-1 the majority
of the heat is generated in the power transistor section.
The value for RQSA depends on the heat sink type, while
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 application note ÒThermal Management for
Linear Regulators.Ó
Calculating Power Dissipation and Heat Sink Requirements
The CS5205A-1 linear regulator includes thermal shutdown and safe operating area circuitry to protect the
device. High power regulators such as these usually operate at high junction temperatures so it is important to calculate the power dissipation and junction temperatures
accurately to ensure that an adequate heat sink is used.
The case is connected to VOUT on the CS5205A-1, electrical
isolation may be required for some applications. Thermal
compound should always be used with high current regulators such as these.
The thermal characteristics of an IC depend on the following four factors:
1. Maximum Ambient Temperature TA (¡C)
2. Power dissipation PD (Watts)
3. Maximum junction temperature TJ (¡C)
4. Thermal resistance junction to ambient RQJA (C/W)
These four are related by the equation
TJ = TA + PD ´ RQJA
(3)
(1)
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.
5
CS5205A-1
Applications Information: continued
CS5205A-1
Package Specification
PACKAGE DIMENSIONS IN mm(INCHES)
PACKAGE THERMAL DATA
Thermal Data
RQJC
RQJA
3L
TO-220
1.6
50
typ
typ
3L
D2PAK
1.6
10 - 50*
ûC/W
ûC/W
*Depending on thermal properties of substrate. RQJA = RQJC + RQCA
3 Lead TO-220 (T) Straight
3 Lead D2PAK (DP)
10.31 (.406)
10.05 (.396)
4.83 (.190)
4.06 (.160)
10.54 (.415)
9.78 (.385)
6.55 (.258)
5.94 (.234)
1.40 (.055)
1.14 (.045)
1.40 (.055)
1.14 (.045)
20° typ
3.96 (.156)
3.71 (.146)
2.87 (.113)
2.62 (.103)
1.88 (.066)
1.40 (.055)
6°
4°
8.53 (.336)
8.28 (.326)
B
14.99 (.590)
14.22 (.560)
15.75 (.620)
14.73 (.580)
2.74(.108)
2.49(.098)
EÐPIN
6°
4°
0.10(.004)
0.00(.000)
1.40 (.055)
1.14 (.045)
1.52 (.060)
1.14 (.045)
14.22 (.560)
13.72 (.540)
2.79 (.110)
2.29 (.090)
0.91 (.036)
0.66 (.026)
6.17 (.243) REF
2.54 (.100) REF
A
3°
0°
1.40 (.055)
1.14 (.045)
6°
4°
(Both Sides)
B
4.57 (.180)
4.31 (.170)
1.02 (.040)
0.63 (.025)
C
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
Type
CS5205A-1GT3
5A, adj. output
CS5205A-1GDP3 5A, adj. output
CS5205A-1GDPR3 5A, adj. output
Rev. 7/8/97
Description
3L TO-220 Straight
3L D2PAK
3L D2PAK
(tape & reel)
Cherry Semiconductor Corporation reserves the
right to make changes to the specifications without
notice. Please contact Cherry Semiconductor
Corporation for the latest available information.
6
© 1999 Cherry Semiconductor Corporation