1
Features
s
Output Current to 1.5A
s
Output Accuracy to 1.5%
Over Temperature
s
Dropout Voltage (typical)
1.05V @ 1.5A
s
Fast Transient Response
s
Fault Protection
Current Limit
Thermal Shutdown
Package Options
3L TO-220
Tab (V
OUT
)
CS52015-3
1.5A, 3.3V Fixed Linear Regulator
1
CS52015-3
The CS52015-3 linear regulator pro-
vides 1.5A at 3.3V with an output
voltage accuracy of 1.5%.
The regulator is intended for use as
a post regulator and microprocessor
supply. The fast loop response and
low dropout voltage make this reg-
ulator ideal for applications where
low voltage operation and good
transient response are important.
The circuit is designed to operate
with dropout voltages less than
1.4V at 1.5A output current. The
maximum quiescent current is only
10mA at full load. Device protec-
tion includes overcurrent and ther-
mal shutdown.
The CS52015-3 is pin compatible
with the LT1086 family of linear
regulators but has lower dropout
voltage.
The regulator is available in TO-
220, surface mount D
2
, and SOT-223
packages.
Application Diagram
Consult factory for other fixed output voltage
options.
CS52015 -3
1
Gnd
2
V
OUT (tab)
3
V
IN
Description
3L D
2
PAK
Tab (V
OUT
)
1
A Company
CS52015-3
V
IN
Gnd
3.3V
@ 1.5A
22
mF
5V
10
mF
5V
V
OUT
3L SOT-223
Tab (V
OUT
)
1
Rev. 2/17/98
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
2
CS52015-3
Absolute Maximum Ratings
Supply Voltage, V
IN
.....................................................................................................................................................................7V
Operating Temperature Range................................................................................................................................-40C to 70C
Junction Temperature ............................................................................................................................................................150C
Storage Temperature Range ..................................................................................................................................-60C to 150C
Lead Temperature Soldering
Wave Solder (through hole styles only) .....................................................................................10 sec. max, 260C peak
Reflow (SMD styles only) ......................................................................................60 sec. max above 183C, 230C peak
ESD Damage Threshold............................................................................................................................................................2kV
PACKAGE PIN #
PIN SYMBOL
FUNCTION
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Electrical Characteristics:
C
IN
= 10F, C
OUT
= 22F Tantalum, V
OUT
+ V
DROPOUT
< V
IN
< 7V, 0C T
A
70C, T
J
+150C,
unless otherwise specified, I
full load
= 1.5A.
Package Pin Description
s Fixed Output Voltage
Output Voltage
V
IN
V
OUT
=1.5V
3.250
3.300
3.350
V
(Notes 1 and 2)
0I
OUT
1.5A
(-1.5%)
(+1.5%)
Line Regulation
2VV
IN
V
OUT
3.7V; I
OUT
=10mA
0.02
0.20
%
Load Regulation
V
IN
V
OUT
=2V; 10mA I
OUT
1.5A 0.04
0.4
%
(Notes 1 and 2)
Dropout Voltage (Note 3)
I
OUT
=1.5A
1.05
1.4
V
Current Limit
V
IN
V
OUT
=3V
1.6
3.1
A
Quiescent Current
I
OUT
=10mA
5.0
10.0
mA
Thermal Regulation (Note 4)
30ms pulse; T
A
=25C
0.002
0.020
%/W
Ripple Rejection
f=120Hz; I
OUT
=1.5A; V
IN
V
OUT
=3V; 80
dB
(Note 4)
V
RIPPLE
=1V
P-P
Thermal Shutdown (Note 5)
150
180
210
C
Thermal Shutdown Hysteresis
25
C
(Note 5)
Note 1: Load regulation and output voltage are measured at a constant junction temperature by low duty cycle pulse testing. Changes in out-
put 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 1/4 from the bottom of the package.
Note 3: Dropout voltage is a measurement of the minimum input/output differential at full load.
Note 4: Guaranteed by design, not tested in production.
Note 5: Thermal shutdown is 100% functionally tested in production.
D
2
PAK
TO-220
SOT-223
1
1
1
Gnd
Ground connection
2
2
2
V
OUT
Regulated output voltage (case).
3
3
3
V
IN
Input voltage
CS52015-3
3
Block Diagram
1500
1200
900
600
300
0
0.75
0.80
0.85
0.90
0.95
1.00
1.05
I
OUT
(mA)
V Drop Out (V)
T
CASE
0C
T
CASE
125C
T
CASE
25C
0
10
130
-0.12
0.10
Output V
oltage Deviation (%)
T
J
(
C)
20
30
40
50
60
70
80
90 100 110 120
0.08
0.06
0.04
0.02
0.00
-0.02
-0.04
-0.06
-0.08
-0.10
Dropout Voltage vs Output Current
Output Voltage vs. Temperature
Error
Amplifier
+
Output
Current
Limit
-
V
IN
V
OUT
Gnd
Thermal
Shutdown
Bandgap
Typical Performance Characteristics
15
10
1
Frequency (Hz)
Ripple Rejection (dB)
25
35
45
55
65
75
85
10
2
10
3
10
4
10
6
10
5
T
CASE
= 25
C
I
OUT
= 1.5A
(V
IN
V
OUT
) = 3V
V
RIPPLE
= 1.0V
PP
Ripple Rejection vs. Frequency
1.5
2.5
3.0
3.5
1.5
I
SC
(A)
V
IN
- V
OUT
(V)
1.7
1.9
2.1
2.3
3.1
3.3
1.0
4.0
2.5
2.7
2.9
3.5
2.0
4.5
5.0
6.0
5.5
6.5
7.0
Short Circuit Current vs V
IN
-V
OUT
4
CS52015-3
Applications Information
The CS52015-3 linear regulator provides a 3.3V output
voltage at currents up to 1.5A. The regulator is protected
against overcurrent conditions and includes thermal
shutdown.
The CS52015-3 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.
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 are based on cost, availabili-
ty, size and temperature constraints. A tantalum or alu-
minum 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 solu-
tion. However, when the circuit operates at low tempera-
tures, both the value and ESR of the capacitor will vary
considerably. The capacitor manufacturers data sheet pro-
vides this information.
A 22F tantalum capacitor will work for most applications,
but with high current regulators such as the CS52015-3 the
transient response and stability improve with higher val-
ues of capacitance. The majority of applications for this
regulator involve large changes in load current so the out-
put capacitor must supply the instantaneous load current.
The ESR of the output capacitor causes an immediate drop
in output voltage given by:
V = I
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.
When large external capacitors are used with a linear regu-
lator 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 capaci-
tor, the output voltage and the rate at which V
IN
drops. In
the CS52015-3 linear regulator, the discharge path is
through a large junction and protection diodes are not usu-
ally needed. If the regulator is used with large values of
output capacitance and the input voltage is instantaneous-
ly shorted to ground, damage can occur. In this case, a
diode connected as shown in Figure 1 is recommended.
Figure 1: Protection diode scheme for large output capacitors.
Since the CS52015-3 is a three terminal regulator, it is not
possible to provide true remote load sensing. Load regula-
tion is limited by the resistance of the conductors connect-
ing the regulator to the load. For best results the regulator
should be connected as shown in Figure 2.
Output Voltage Sensing
V
OUT
V
IN
CS52015-3
V
IN
Gnd
C
1
V
OUT
C
2
IN4002 (optional)
Protection Diodes
Stability Considerations
Typical Performance Characteristics
0
2
3
4
5
6
750
V
oltage Deviation (mV)
7
-100
0
100
200
Time
mS
Load Step (mA)
10
9
8
1
1500
-200
0
C
OUT
=C
IN
=22
mF Tantalum
Transient Response
Load Regulation vs. Output Current
0.025
0.000
0.050
0.075
0.100
0
1
2
Output Current (A)
Output V
oltage Deviation (%)
T
CASE
= 0
C
T
CASE
= 125
C
T
CASE
= 25
C
5
CS52015-3
Applications Information: continued
Figure 2: Conductor parasitic resistance effects can be minimized with
the above grounding scheme for fixed output regulators.
The CS52015-3 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 V
OUT
on the CS52015-3, and elec-
trical isolation may be required for some applications.
Thermal compound should always be used with high cur-
rent regulators such as these.
The thermal characteristics of an IC depend on the follow-
ing four factors:
1. Maximum Ambient Temperature T
A
(C)
2. Power dissipation P
D
(Watts)
3. Maximum junction temperature T
J
(C)
4. Thermal resistance junction to ambient R
QJA
(C/W)
These four are related by the equation
T
J
= T
A
+ P
D
R
QJA
(1)
The maximum ambient temperature and the power dissi-
pation 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:
P
D(max)
={V
IN(max)
V
OUT(min)
}I
OUT(max)
+V
IN(max)
I
Q
(2)
where
V
IN(max)
is the maximum input voltage,
V
OUT(min)
is the minimum output voltage,
I
OUT(max)
is the maximum output current, for the application
I
Q
is the maximum quiescent current at I
OUT
(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 R
QJA
, the total thermal resistance between the
junction and the surrounding air.
1. Thermal Resistance of the junction to case, R
QJC
(C/W)
2. Thermal Resistance of the case to Heat Sink, R
QCS
(C/W)
3. Thermal Resistance of the Heat Sink to the ambient air,
R
QSA
(C/W)
These are connected by the equation:
R
QJA
= R
QJC
+ R
QCS
+ R
QSA
(3)
The value for R
QJA
is calculated using equation (3) and the
result can be substituted in equation (1).
The value for R
QJC
is 3.5C/W. For a high current regulator
such as the CS52015-3 the majority of the heat is generated
in the power transistor section. The value for R
QSA
depends on the heat sink type, while R
QCS
depends on fac-
tors such as package type, heat sink interface (is an insula-
tor and thermal grease used?), and the contact area
between the heat sink and the package. Once these calcula-
tions are complete, the maximum permissible value of
R
QJA
can be calculated and the proper heat sink selected.
For further discussion on heat sink selection, see applica-
tion note Thermal Management for Linear Regulators.
Calculating Power Dissipation and Heat Sink Requirements
V
OUT
V
IN
CS52015-3
V
IN
R
C
R
LOAD
conductor
parasitic resistance
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