1
Features
Error
Amplifier
+
Output
Current
Limit
-
V
IN
V
OUT
Adj
Thermal
Shutdown
Bandgap
s
Output Current to 7A
s
Output Trimmed to 1.5%
s
Dropout Voltage
1.4V @ 7A
s
Fast Transient Response
s
Fault Protection Circuitry
Thermal Shutdown
Overcurrent Protection
Safe Area Protection
s
3.3V Fixed Version
Available
Package Options
3L TO-220
Tab (V
OUT
)
CS5207-1
7A Adjustable Linear Regulator
1
CS5207-1
The CS5207-1 linear regulator pro-
vides 7A at adjustable voltages
with an accuracy of 1.5%. Two
external resistors are used to set the
output voltage within a 1.25V to
13V range.
The regulator is intended for use as
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 as low as 1V
depending on the output current
level. The maximum quiescent cur-
rent is only 10mA at full load.
The regulator is fully protected
against overload conditions with
protection circuitry for Safe
Operating Area (SOA), overcurrent
and thermal shutdown.
The regulator is available in a
TO-220 package. A 3.3V, fixed ver-
sion is also available. Please consult
factory for more information.
Block Diagram
1
Adj
2
V
OUT
3
V
IN
Description
A 3.3V fixed version is also available.
*Consult factory.
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
A Company
Rev. 7/8/97
2
CS5207 -1
Absolute Maximum Ratings
Supply Voltage, V
CC
..................................................................................................................................................................17V
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
Electrical Characteristics:
C
IN
= 10F, C
OUT
= 22F Tantalum, V
IN
V
OUT
=3V, V
IN
15V, 0C T
A
70C, T
J
+150C,
unless otherwise specified, I
full load
= 7A.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Package Pin Description
PACKAGE PIN #
PIN SYMBOL
FUNCTION
s Adjustable Output Voltage
Reference Voltage
V
IN
V
OUT
=1.6V; V
Adj
= 0V
1.235
1.254
1.272
V
(Notes 1 and 2)
10mAI
OUT
7A
(-1.5%)
(+1.5%)
Line Regulation
1.6VV
IN
V
OUT
6V; I
OUT
=10mA
0.04
0.20
%
Load Regulation
V
IN
V
OUT
=1.6V;
0.13
0.5
%
(Notes 1 and 2)
10mAI
OUT
7A
Dropout Voltage (Note 3)
I
OUT
=7A
1.4
1.55
V
Current Limit
V
IN
V
OUT
=3V; T
J
25C
7.1
8.5
A
V
IN
V
OUT
=9V
1.0
A
Minimum Load Current
V
IN
V
OUT
=7V
1.2
6
mA
Adjust Pin Current
50
100
A
Adjust Pin Current Change
1.6VV
IN
V
OUT
4V; 0.2
5.0
A
10mAI
OUT
7A
Thermal Regulation
30ms pulse; T
A
=25C
0.003
%W
Ripple Rejection
f=120Hz; C
Adj
=25F; I
OUT
=7A
80
dB
Temperature Stability
0.5
%
RMS Output Noise
10Hzf10kHz; T
A
=25C
0.003
%V
OUT
Thermal Shutdown
150
180
C
Thermal Shutdown Hysteresis
25
C
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 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 1/4 from the bottom of the package.
Note 3: Dropout voltage is a measurement of the minimum input/output differential at full load.
3L TO-220
1
Adj
Adjust pin (low side of the internal reference).
2
V
OUT
Regulated output voltage (case).
3
V
IN
Input voltage.
0.025
0.000
0.050
0.075
0.100
0.200
Output V
oltage Deviation (%)
0
1
2
3
4
5
Output Current (A)
T
CASE
= 0
C
6
7
0.125
0.150
0.175
T
CASE
= 125
C
T
CASE
= 25
C
0
1
2
3
4
5
6
Dropout V
oltage (V)
Output Current (A)
7
0.85
0.70
0.80
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
1.35
T
CASE
= 0
C
T
CASE
= 125
C
0.75
1.40
1.45
1.50
1.55
T
CASE
= 25C
CS5207 -1
3
Typical Performance Characteristics
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
Reference Voltage vs. Temperature
Load Regulation vs. Output Current
1
2
3
4
5
6
0.550
Minimum Load Current (mA)
V
IN
V
OUT
(V)
T
CASE
= 0
C
T
CASE
= 125
C
7
0.875
1.200
1.525
1.850
2.175
2.500
8
9
T
CASE
= 25
C
Minimum Load Current
0.0
10
1
Frequency (Hz)
Ripple Rejection (dB)
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
10
2
10
3
10
4
10
5
T
CASE
= 25
C
I
OUT
= 7A
(V
IN
V
OUT
) = 3V
V
RIPPLE
= 1.6V
PP
C
Adj
= 25
mF
Ripple Rejection vs. Frequency
4
CS5207 -1
The CS5207-1 linear regulator provides adjustable volt-
ages at currents up to 7A. 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 CS5207-1 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.
The adjustable regulator 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 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
50A) 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
(
)
+ I
Adj
R2
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
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.
Figure 1. Resistor divider scheme for the adjustable version.
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 manufacturers data sheet pro-
vides this information.
A 22F tantalum capacitor will work for most applications,
but with high current regulators such as the CS5207-1 the
transient response and stability improve with higher val-
ues of capacitor. The majority of applications for this regu-
lator 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:
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 net-
work 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 CS5207-1 regulator, the discharge path is through a
large junction and protection diodes are not usually need-
ed. If the regulator is used with large values of output
capacitance and the input voltage is instantaneously short-
ed to ground, damage can occur. In this case, a diode con-
nected as shown in Figure 2 is recommended.
Figure 2. Protection diode scheme for adjustable output regulator.
Since the CS5207-1 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.
Output Voltage Sensing
V
OUT
V
IN
CS5207-1
V
IN
Adj
R
1
R
2
C
1
V
OUT
C
2
C
Adj
IN4002 (optional)
Protection Diodes
Stability Considerations
V
OUT
V
IN
CS5207-1
V
IN
Adj
R
1
R
2
C
1
V
OUT
C
2
V
REF
I
Adj
C
Adj
R1 + R2
R1
Adjustable Operation
Applications Information
5
CS5207 -1
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, R
C
is multiplied by the divider
ratio and the effective resistance between the regulator and
the load becomes
R
C
(
)
R
C
= conductor parasitic resistance
Figure 3. Grounding scheme for the adjustable output regulator to min-
imize parasitics.
The CS5207-1 linear regulator includes thermal shutdown
and safe operating area circuitry to protect the device.
High power regulators such as this 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 CS5207-1, electrical
isolation may be required for some applications. Thermal
compound should always be used with high current regu-
lators 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 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 CS5207-1 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 factors such as package type, heat sink inter-
face (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 R
QJA
can be calculated and the proper heat sink
selected. For further discussion on heat sink selection, see
application note Thermal Management for Linear
Regulators.
Calculating Power Dissipation and Heat Sink Requirements
V
OUT
R
C
V
IN
conductor parasitic
resistance
CS5207-1
V
IN
Adj
R
LOAD
R
1
R
2
R1 + R2
R1
Applications Information: continued
Part Number
Type
Description
CS5207-1GT3
7A, adj. output
3 L TO-220 Straight
CS5207-3GT3
7A, fixed output
3L TO-220 Straight
6
Ordering Information
Rev. 7/8/97
CS5207 -1
Package Specification
PACKAGE DIMENSIONS IN mm(INCHES)
Thermal Data
3L
TO-220
R
Q
JC
typ
1.6
C/W
R
Q
JA
typ
50
C/W
PACKAGE THERMAL DATA
1999 Cherry Semiconductor Corporation
Cherry Semiconductor Corporation reserves the
right to make changes to the specifications without
notice. Please contact Cherry Semiconductor
Corporation for the latest available information.
3 Lead TO-220 (T) Straight
5.33 (.210)
4.83 (.190)
2.79 (.110)
2.29 (.090)
1.02 (.040)
0.63 (.025)
0.56 (.022)
0.38 (.014)
1.40 (.055)
1.14 (.045)
4.83 (.190)
4.06 (.160)
6.17 (.243) REF
1.14 (.045)
1.52 (.060)
1.14 (.045)
1.40 (.055)
2.87 (.113)
2.62 (.103)
6.55 (.258)
5.94 (.234)
14.22 (.560)
13.72 (.540)
2.92 (.115)
2.29 (.090)
9.78 (.385)
10.54 (.415)
3.71 (.146)
3.96 (.156)
14.99 (.590)
14.22 (.560)
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