CHERRY CS5201

CS5201-1
CS5201-1
1A Adjustable Linear Regulator
Description
The CS5201-1 linear regulator
provides 1A with an output
voltage accuracy of ±1%. The
device uses two external resistors to set the output voltage
within a 1.25V to 5.5V range.
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.
Features
The circuit is designed to operate with dropout voltages less
than 1.2V at 1A output current.
Device protection includes overcurrent and thermal shutdown.
The CS5201 is pin compatible
with the LT1086 family of linear
regulators.
The regulator is available in
TO-220, surface mount D2, and
SOT-223 packages.
■ Output Current to 1A
■ Output Accuracy to ±1%
over Temperature
■ Dropout Voltage (typical)
1.0V @ 1A
■ Fast Transient Response
■ Fault Protection
Current Limit
Thermal Shutdown
Package Options
Application Diagram
5V
3L TO-220
3L D2PAK
Tab (VOUT)
Tab (VOUT)
VOUT
VIN
3.3V @ 1A
CS5201-1
1
124W
1%
Adj
3L SOT-223
Tab (VOUT)
1
22mF
5V
10mF
5V
0.1mF
5V Tant
200W
1%
CS5201 -1
1 Adj
2 VOUT(Tab)
3 VIN
1
Consult factory for fixed output
voltage versions.
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. 2/16/98
1
A
¨
Company
CS5201-1
Absolute Maximum Ratings
Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7V
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
ESD Damage Threshold (Human Body Model) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2kV
Electrical Characteristics: CIN = 10µF, COUT = 22µF Tantalum, VOUT + VDROPOUT < VIN < 7V, 0¡C ² TA ² 70¡C, TJ ² +150¡C,
unless otherwise specified, Ifull load = 1A.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Reference Voltage
(Notes 1 and 2)
VINÐVOUT=1.5V; VAdj = 0V
10mA²IOUT²1A
1.241
(-1%)
1.254
1.266
(+1%)
V
Line Regulation
1.5V²VINÐVOUT²5.75V; IOUT=10mA
0.02
0.20
%
Load Regulation
(Notes 1 and 2)
VINÐVOUT=1.5V; 10mA²IOUT²1A
0.04
0.4
%
Dropout Voltage (Note 3)
IOUT=1A
1.0
1.2
V
Current Limit
VINÐVOUT=3V; TJ ³ 25¡C
■ Adjustable Output Voltage
1.1
3.1
A
Minimum Load Current (Note 4) VIN=7V ; VAdj=0
0.6
2.0
mA
Adjust Pin Current
VINÐVOUT=3V; IOUT=10mA
50
100
µA
Thermal Regulation (Note 5)
30ms pulse; TA=25¡C
0.002
0.020
%/W
Ripple Rejection (Note 5)
f=120Hz; IOUT=1A; VINÐVOUT=3V;
VRIPPLE=1VPP
80
Thermal Shutdown (Note 6)
150
Thermal Shutdown Hysteresis
(Note 6)
180
dB
210
25
¡C
¡C
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 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.
Note 4: 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 requirement.
Note 5: Guaranteed by design, not 100% tested in production.
Note 6: Thermal shutdown is 100% functionally tested in production.
Package Pin Description
PACKAGE PIN #
PIN SYMBOL
FUNCTION
D2PAK
TO-220
SOT-223
1
1
1
Adj
Adjust pin (low side of the internal reference).
2
2
2
VOUT
Regulated output voltage (case).
3
3
3
VIN
Input voltage.
2
CS5201-1
Block Diagram
V OUT
V IN
Output
Current
Limit
Thermal
Shutdown
-
+
Error
Amplifier
Bandgap
Reference
Adj
Typical Performance Characteristics
1.00
TCASE
0.10
= 0°C
0.08
Output Voltage Deviation (%)
0.95
TCASE = 25°C
VDropout (V)
0.90
0.85
TCASE = 125°C
0.80
0.06
0.04
0.02
0.00
-0.02
-0.04
-0.06
-0.08
-0.10
0.75
-0.12
0
200
400
600
800
1000
0
10
20
30
40
50
IOUT (mA)
70
80
90 100 110 120 130
Reference Voltage vs. Temperature
Dropout Voltage vs. Output Current
0.100
0.65
Minimum Load Current (mA)
Output Voltage Deviation (%)
60
TJ (°C)
0.075
0.050
TCASE = 125°C
TCASE = 25°C
0.025
0.60
TCASE = 0°C
0.55
TCASE = 125°C
TCASE = 25°C
0.50
0.45
CIN =COUT =22mF Tantalum
TCASE = 0°C
0.000
0.40
0
1
Output Current (A)
2
1
Load Regulation vs. Output Current
2
3
4
VIN – VOUT (V)
Minimum Load Current vs VIN-VOUT
3
5
6
7
CS5201-1
Typical Performance Characteristics: continued
70.0
85
IO = 10mA
75
Ripple Rejection (dB)
Adjust Pin Current (mA)
65.0
60.0
55.0
50.0
65
55
TCASE = 25°C
IOUT = 1A
(VIN Ð VOUT) = 3V
VRIPPLE = 1.0VPP
CAdj = 0.1mF
45
35
45.0
25
15
40.0
0
10
20
30
40
50
60
70
80
101
90 100 110 120 130
102
103
Temperature (°C)
106
Ripple Rejection vs. Frequency
3.5
200
3.3
3.1
100
2.9
0
2.7
-100
VOUT = 3.3V
COUT= CIN = 22mF Tantalum
CAdj= 0.1mF
-200
ISC(A)
Voltage Deviation (mV)
105
Frequency (Hz)
Adjust Pin Current vs. Temperature
Load Step (mA)
104
2.5
2.3
1000
2.1
500
1.9
1.7
0
0
1
2
3
4
5
6
7
8
9
10
1.5
Time mS
1.0
1.5
2.0
2.5
3.0
3.5
4.0
VIN - VOUT (V)
Transient Response
Short Circuit Current vs. VIN - VOUT
Applications Information
The CS5201-1 linear regulator provides adjustable voltages at currents up to 1A. The regulator is protected
against overcurrent conditions and includes thermal
shutdown.
The CS5201-1 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.
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 = 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
2mA. R1 and R2 should be the same type, e.g. metal film
for best tracking over temperature. While not required, a
bypass capacitor from the adjust pin to ground will
improve ripple rejection and transient response. A 0.1µF
tantalum capacitor is recommended for Òfirst cutÓ design.
Type and value may be varied to obtain optimum performance vs. price.
Adjustable Operation
The CS5201-1 has an output voltage range of 1.25V to 5.5V.
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
4
CS5201-1
Applications Information: continued
EXTERNAL SUPPLY
VIN
VOUT
VIN
C1
CS5201-1
VOUT
VREF
R1
C2
Adj
VIN
VOUT
IAdj
CAdj
VAdj
R2
VOUT
Figure 1. Resistor divider scheme.
Short Circuit Protection
The CS5201-1 linear regulator has an absolute maximum
specification of 7V for the voltage difference between VIN
and VOUT. However, the IC may be used to regulate voltages in excess of 7V. The main considerations in such a
design are power-up and short circuit capability.
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 load as soon as the VIN to VOUT differential is
large enough that the pass transistor conducts current. The
load at this point is essentially at ground, and the supply
voltage is on the order of several hundred millivolts, with
the result that the pass transistor is in dropout. As the supply to VIN increases, the pass transistor will remain in
dropout, and current is passed to the load until VOUT
reaches the point at which the IC is in regulation. Further
increase in the supply voltage 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 7V is not exceeded.
Figure 2. Short Circuit Protection Circuit for High Voltage Application.
Stability Considerations
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 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 manufacturersÕ data sheet provides this information.
A 22µF tantalum capacitor will work for most applications,
but with high current regulators such as the CS5201 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:
ÆV = ÆI ´ ESR
However, the possibility of destroying the IC in a short
circuit condition is very real for this type of design. Short
circuit conditions will result in the immediate operation of
the pass transistor outside of its safe operating area. Overvoltage 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 the VIN to VOUT differential to less than 7V if failsafe operation is required. One possible clamp circuit is
illustrated in figure 2; 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 condition indefinitely
while protecting the IC.
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 CS5201-1 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 Figure 3 is recommended.
5
CS5201-1
Applications Information: continued
IN4002
VIN
(optional)
VOUT
VIN
C1
The thermal characteristics of an IC depend on the following four factors:
1. Maximum Ambient Temperature TA (¡C)
VOUT
2. Power dissipation PD (Watts)
CS5201-1
3. Maximum junction temperature TJ (¡C)
R1
4. Thermal resistance junction to ambient RQJA (C/W)
C2
Adj
These four are related by the equation
TJ = TA + PD ´ RQJA
R2
CAdj
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.
Figure 3. Protection diode for large output capacitors.
The maximum power dissipation for a regulator is:
Output Voltage Sensing
PD(max)={VIN(max)ÐVOUT(min)}IOUT(max)+VIN(max)IQ
Since the CS5201-1 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.
(
VIN(max) is the maximum input voltage,
VOUT(min) is the minimum output voltage,
IOUT(max) is the maximum output current, for the application
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.
)
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.
RC = conductor parasitic resistance
VIN
RC
VOUT
VIN
CS5201-1
(2)
where
For the adjustable regulator, the best load regulation
occurs when R1 is connected directly to the output pin of
the regulator as shown in Figure 4. 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
(1)
conductor parasitic
resistance
1. Thermal Resistance of the junction to case, RQJC (¡C/W)
2. Thermal Resistance of the case to Heat Sink, RQCS (¡C/W)
RLOAD
R1
3. Thermal Resistance of the Heat Sink to the ambient air,
RQSA (¡C/W)
R2
These are connected by the equation:
Adj
RQJA = RQJC + RQCS + RQSA
(3)
The value for RQJA is calculated using equation (3) and the
result can be substituted in equation (1).
Figure 4. Grounding scheme for the adjustable output regulator to minimize parasitic resistance effects.
The value for RQJC is 3.5ûC/W for a given package type
based on an average die size. For a high current regulator
such as the CS5201-1 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 CS5201-1 linear regulator includes thermal shutdown
and current limit 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 CS5201-1, and electrical isolation may be required for some applications.
Thermal compound should always be used with high current regulators such as these.
6
CS5201-1
Package Specification
PACKAGE THERMAL DATA
PACKAGE DIMENSIONS IN mm (INCHES)
3 Lead TO-220 (T) Straight
4.83 (.190)
4.06 (.160)
10.54 (.415)
9.78 (.385)
6.55 (.258)
5.94 (.234)
Thermal Data
RQJC
typ
RQJA
typ
3L
D2PAK
3.5
10 - 50*
3L
SOT-223
15
156
ûC/W
ûC/W
*Depending on thermal properties of substrate. RQJA = RQJC + RQCA
1.40 (.055)
1.14 (.045)
3.96 (.156)
3.71 (.146)
2.87 (.113)
2.62 (.103)
3 Lead SOT-223 (ST)
14.99 (.590)
14.22 (.560)
6.70 (.264)
6.30 (.248)
7.30 (.287)
6.70 (.264)
1.52 (.060)
1.14 (.045)
14.22 (.560)
13.72 (.540)
3L
TO-220
3.5
50
3.15 (.124)
2.95 (.116)
6.17 (.243) REF
1.40 (.055)
1.14 (.045)
3.70 (.146)
3.30 (.130)
1.02 (.040)
0.63 (.025)
0.56 (.022)
0.38 (.014)
2.79 (.110)
2.29 (.090)
5.33 (.210)
4.83 (.190)
2.30 (.090)
2.92 (.115)
2.29 (.090)
0.35 (.014)
0.25 (.010)
1.70 (.067)
1.50 (.060)
0.10 (.004)
0.02 (.001)
3 Lead D2PAK (DP)
10.31 (.406)
10.05 (.396)
1.05 (.041)
0.85 (.033)
0.85 (.033)
0.65 (.026)
1.30 (.051)
1.10 (.043)
10° MAX
4.60 (.181)
1.40 (.055)
1.14 (.045)
1.68 (.066)
1.40 (.055)
8.53 (.336)
8.28 (.326)
15.75 (.620)
14.73 (.580)
2.74(.108)
2.49(.098)
1.40 (.055)
1.14 (.045)
2.79 (.110)
2.29 (.090)
0.91 (.036)
0.66 (.026)
2.54 (.100) REF
4.57 (.180)
4.31 (.170)
.254 (.010) REF
0.10 (.004)
0.00 (.000)
Ordering Information
Part Number
CS5201-1GT3
CS5201-1GDP3
CS5201-1GDPR3
CS5201-1GST3
CS5201-1GSTR3
Rev. 2/16/98
Type
1A, adj. output
1A, adj. output
1A, adj. output
1A, adj. output
1A, adj. output
Description
3 L TO-220 Straight
3 L D2PAK
3 L D2PAK (tape & reel)
3 L SOT-223
3 L SOT-223 (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.
7
© 1999 Cherry Semiconductor Corporation