CS52015-1
CS52015-1
1.5A Adjustable Linear Regulator
Description
The CS52015-1 linear regulator pro-
vides 1.5A with an accuracy of ±1%.
The device uses two external resis-
tors to set the output voltage within
a 1.25V to 5.5V range.
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. Device
protection includes overcurrent and
thermal shutdown.
The CS52015-1 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.
Features
s
Output Current to 1.5A
s
Output Accuracy to ±1%
Over Temperature
s
Dropout Voltage (typical)
1.05V @ 1.5A
s
Fast Transient Response
s
Fault Protection
Current Limit
Thermal Shutdown
Application Diagram
Package Options
3L TO-220
5.0V
Tab (V
OUT
)
3L D
2
PAK
Tab (V
OUT
)
V
IN
V
OUT
CS52015-1
Adj
124W
1%
3.3V @ 1.5A
1
10
mF
5V
22mF
5V
0.1mF
5V
Tantalum
SOT-223
200W
1%
1
Tab (V
OUT
)
CS52015 -1
1 Adj
2 V
OUT (Tab)
3 V
IN
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. 2/17/98
1
A
¨
Company
CS52015-1
Absolute Maximum Ratings
Supply Voltage, V
CC
....................................................................................................................................................................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............................................................................................................................................................2kV
Electrical Characteristics:
C
IN
= 10µF, C
OUT
= 22µF Tantalum, V
OUT
+ V
DROPOUT
< V
IN
< 7V, 0¡C ² T
A
² 70¡C, T
J
² +150¡C,
unless otherwise specified, I
full load
= 1.5A.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
s
Adjustable Output Voltage (CS52015-1)
Reference Voltage
(Notes 1 and 2)
Line Regulation
Load Regulation
(Notes 1 and 2)
Dropout Voltage (Note 3)
Current Limit
Adjust Pin Current
Thermal Regulation (Note 5)
Ripple Rejection (Note 5)
Thermal Shutdown (Note 6)
Thermal Shutdown Hysteresis
(Note 6)
V
IN
ÐV
OUT
=1.5V; V
Adj
= 0V
10mA²I
OUT
²1.5A
1.5V²V
IN
ÐV
OUT
²5.75V; I
OUT
=10mA
V
IN
ÐV
OUT
=1.5V; 10mA²I
OUT
²1.5A
I
OUT
=1.5A
V
IN
ÐV
OUT
=3V; T
J
³ 25¡C
V
IN
ÐV
OUT
=3V; I
OUT
=10mA
30ms pulse; T
A
=25¡C
f=120Hz; I
OUT
=1.5A; V
IN
ÐV
OUT
=3V;
V
RIPPLE
=1V
PP
150
1.6
1.241
(-1%)
1.254
0.02
0.04
1.05
3.1
0.6
50
0.002
80
180
25
210
2.0
100
0.020
1.266
(+1%)
0.20
0.4
1.4
V
%
%
V
A
mA
µA
%/W
dB
¡C
¡C
Minimum Load Current (Note 4) V
IN
=7V ; V
Adj
=0
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 1/4Ó 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 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
D
2
PAK
1
2
3
TO-220
1
2
3
SOT-223
1
2
3
Adj
V
OUT
V
IN
Adjust pin (low side of the internal reference.
Regulated output voltage (case).
Input voltage
2
CS52015-1
Block Diagram
V
OUT
V
IN
Output
Current
Limit
Thermal
Shutdown
-
+
Error
Amplifier
Adj
Bandgap
Typical Performance Characteristics
1.05
0.10
0.08
T
CASE
0ûC
Output Voltage Deviation (%)
1.00
V Drop Out (V)
0.06
0.04
0.02
0.00
-0.02
-0.04
-0.06
-0.08
-0.10
-0.12
0
10
20
30
40
50
60
70
80
90 100 110 120 130
0.95
T
CASE
25ûC
0.90
0.85
0.80
T
CASE
125ûC
0.75
0
300
600
I
OUT
(mA)
900
1200
1500
T
J
(°C)
Dropout Voltage vs. Output Current
Reference Voltage vs. Temperature
0.100
0.65
Minimum Load Current (mA)
Output Voltage Deviation (%)
0.60
T
CASE
= 0°C
0.55
T
CASE
= 125°C
0.50
T
CASE
= 25°C
0.075
0.050
T
CASE
= 125°C
T
CASE
= 25°C
0.025
0.45
C
IN
=C
OUT
=22mF Tantalum
0.40
T
CASE
= 0°C
0.000
0
1
Output Current (A)
2
1
2
3
4
V
IN
– V
OUT
(V)
5
6
7
Load Regulation vs. Output Current
Minimum Load Current vs V
IN
-V
OUT
3
CS52015-1
Typical Performance Characteristics
70.0
I
O
= 10mA
65.0
Adjust Pin Current (mA)
Ripple Rejection (dB)
85
75
65
55
45
35
60.0
55.0
50.0
T
CASE
= 25°C
I
OUT
= 1.5A
(V
IN
Ð V
OUT
) = 3V
V
RIPPLE
= 1.0V
PP
C
Adj
= 0.1mF
45.0
25
15
0
10
20
30
40
50
60
70
80
90 100 110 120 130
10
1
10
2
10
3
10
4
10
5
10
6
Temperature (°C)
Frequency (Hz)
40.0
Adjust Pin Current vs. Temperature
Ripple Rejection vs. Frequency
Voltage Deviation (mV)
3.5
200
100
0
3.3
3.1
2.9
2.7
I
SC
(A)
10
-100
-200
V
OUT
=3.3V
C
OUT
=C
IN
=22mF Tantalum
C
Adj
=0.1mF
2.5
2.3
2.1
1.9
Load Step (mA)
1500
750
1.7
0
0
1
2
3
4
5
Time
mS
6
7
8
9
1.5
1.0 1.5
2.0
2.5
3.0
3.5 4.0 4.5
V
IN
- V
OUT
(V)
5.0
5.5
6.0
6.5
7.0
Transient Response
Short Circuit Current vs V
IN
-V
OUT
Applications Information
The CS52015-1 linear regulator provides adjustable volt-
ages at currents up to 1.5A. The regulator is protected
against overcurrent conditions and includes thermal
shutdown.
The CS52015-1 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
50µA) also flows through R2 and adds a small error that
should be taken into account if precise adjustment of V
OUT
is necessary.
The output voltage is set according to the formula:
V
OUT
= V
REF
´
R1 + R2 + I
Adj
´
R2
R1
The term I
Adj
´
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 perfor-
mance vs price.
(
)
The 52015-1 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 cur-
rent 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
CS52015-1
Applications Information: continued
EXTERNAL SUPPLY
V
IN
C
1
V
IN
V
OUT
V
OUT
V
REF
R
1
Adj
C
2
CS52015-1
V
IN
V
OUT
V
Adj
I
Adj
C
Adj
R
2
V
OUT
Figure 1. Resistor divider scheme.
The CS52015-1 linear regulator has an absolute maximum
specification of 7V for the voltage difference between V
IN
and V
OUT
. However, the IC may be used to regulate volt-
ages 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 V
IN
is fairly slow, typically on the order of several tens of mil-
liseconds, while the regulator responds in less than one
microsecond. In this case, the linear regulator begins
charging the load as soon as the V
IN
to V
OUT
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 sup-
ply to V
IN
increases, the pass transistor will remain in
dropout, and current is passed to the load until V
OUT
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 fol-
lows 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 V
IN
to V
OUT
differen-
tial of 7V is not exceeded.
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. Over-
voltage stresses will then cause destruction of the pass
transistor before overcurrent or thermal shutdown circuit-
ry can become active. Additional circuitry may be required
to clamp the V
IN
to V
OUT
differential to less than 7V if fail-
safe operation is required. One possible clamp circuit is
illustrated in figure 2; however, the design of clamp cir-
cuitry 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.
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 capaci-
tor with almost zero ESR can cause instability. The alu-
minum 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 manufacturersÕ data sheet pro-
vides this information.
A 22µF tantalum capacitor will work for most applications,
but with high current regulators such as the CS52015-1 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:
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 net-
work should be as close as possible to the load for the best
results.
Protection Diodes
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 CS52015-1 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 2 is recommended.
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