CHERRY CS5207-2GT3

CS5207-2
CS5207-2
7A, 1.5V Fixed Linear Regulator
Description
The CS5207-2 provides 7A at 1.5V
with an accuracy of ± 2%.
The regulator is intended for use as
an active termination for the GTL
bus on Intel based motherboards.
The fast loop response and low
dropout voltage make these regulators ideal for applications where
low voltage operation and good
transient response are important.
Features
with dropout voltages as low as 1V
depending on the output current
level. The maximum quiescent current is only 10mA at full load.
■ Output Current to 7A
The regulators are fully protected
against overload conditions with
protection circuitry for Safe
Operating Area (SOA), overcurrent
and thermal shutdown.
■ Dropout Voltage
1.45V @ 7A
The CS5207-2 is available in TO-220
packages.
The circuit is designed to operate
■ Output Voltage Trimmed
to ±2%
■ Fast Transient Response
■ Fault Protection Circuitry
Thermal Shutdown
Overcurrent Protection
Safe Area Protection
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
ESD Damage Threshold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2kV
Package Options
3L TO-220
Tab (VOUT)
Block Diagram
V OUT
V IN
1
2
3
Output
Current
Limit
Thermal
Shutdown
-
+
Gnd
VOUT (Tab)
VIN
1
Error
Amplifier
Bandgap
Gnd
Cherry Semiconductor Corporation
2000 South County Trail, East Greenwich, RI 02818
Tel: (401)885-3600 Fax: (401)885-5786
Email: [email protected]
Web Site: www.cherry-semi.com
Rev. 6/12/98
1
A
¨
Company
CS5207-2
Electrical Characteristics: CIN = 10µF, COUT = 22µF Tantalum, VIN Ð VOUT=3V, VIN ² 10V, 0¡C ² TA ² 70¡C, TJ ² +150¡C,
unless otherwise specified, Ifull load = 7A.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
1.47
(-2%)
1.50
1.53
(+2%)
V
0.04
0.20
%
■ Fixed Output Voltage
CS5207-2
(Notes 1 and 2)
VIN Ð VOUT = 1.65V;
0² IOU T ² 7A
Line Regulation
1.65V ² VINÐVOUT ² 6V; IOUT = 10mA
Load Regulation (Notes 1 and 2)
VIN Ð VOUT = 1.65V; 10mA ² IOUT ² 7A
0.08
0.40
%
Dropout Voltage (Note 3)
IOUT = 7A
1.42
1.65
V
Current Limit
VIN Ð VOUT = 3V; TJ ³ 25¡C
VIN Ð VOUT = 12V
7.1
8.5
1.0
A
A
Quiescent Current
VIN ² 9V; IOUT = 10mA
5.0
Thermal Regulation
30ms pulse; TA = 25¡C
0.003
%/W
Ripple Rejection
f = 120Hz; IOUT = 7A
80
dB
Temperature Stability
RMS Output Noise (%VOUT)
10Hz ² f ² 10kHz
Thermal Shutdown
150
Thermal Shutdown Hysteresis
10.0
mA
0.5
%
0.003
%VOUT
180
¡C
25
¡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 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 #
PIN SYMBOL
3L TO-220
1
2
3
FUNCTION
Gnd
VOUT
VIN
Ground connection.
Regulated output voltage (case).
Input voltage.
1.55
1.50
1.45
1.40
1.35
1.30
1.25
1.20
1.15
1.10
1.05
1.00
0.95
0.90
0.85 TCASE = 25°C
0.80
0.75
0.70
0
1
0.10
0.08
Output Voltage Deviation (%)
Dropout Voltage (V)
Typical Performance Characteristics
TCASE = 0°C
TCASE = 125°C
0.06
0.04
0.02
0.00
-0.02
-0.04
-0.06
-0.08
-0.10
-0.12
2
3
4
Output Current (A)
5
6
7
0
10
20
30
40
50
60
70
TJ (°C)
Output Voltage vs. Temperature
Dropout Voltage vs. Output Current
2
80
90 100 110 120 130
CS5207-2
Typical Performance Characteristics: continued
0.200
100.0
90.0
Ripple Rejection (dB)
Output Voltage Deviation (%)
0.175
0.150
0.125
TCASE = 125°C
0.100
0.075
80.0
70.0
60.0
50.0
TCASE = 25°C
30.0
0.050
20.0
TCASE = 0°C
0.025
TCASE = 25°C
IOUT = 7A
(VIN Ð VOUT) = 3V
VRIPPLE = 1.6VPP
40.0
10.0
0.000
0
1
2
3
4
5
0.0
6
7
101
102
103
Output Current (A)
104
105
Frequency (Hz)
Load Regulation vs. Output Current
Ripple Rejection vs Frequency
Applications Information
the CS5207-2 linear regulator provides a fixed 1.5V output at currents up to 7A. The regulator is protected
against short circuit, and includes 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 CS5207-2 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.
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 CS5207-2, 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 1 is recommended.
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 CS5207-2 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:
IN4002
VIN
(optional)
VOUT
VIN
C1
VOUT
CS5207-2
C2
Gnd
ÆV = ÆI ´ ESR
Figure 1. Protection diode scheme for fixed output regulators.
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
3
CS5207-2
Applications Information: continued
PD(max)={VIN(max)ÐVOUT(min)}IOUT(max)+VIN(max)IQ
Output Voltage Sensing
where
Since the CS5207-2 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. For best results the fixed regulators should be connected as shown in Figure 2.
VIN
VOUT
VIN
RC
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.
conductor parasitic
resistance
CS5207-2
(2)
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.
RLOAD
Gnd
1. Thermal Resistance of the junction to case, RQJC (¡C/W)
2. Thermal Resistance of the case to Heat Sink, RQCS (¡C/W)
3. Thermal Resistance of the Heat Sink to the ambient air,
RQSA (¡C/W)
Figure 2. Conductor parasitic resistance effects can be minimized with
the above grounding scheme for fixed output regulators.
These are connected by the equation:
RQJA = RQJC + RQCS + RQSA
Calculating Power Dissipation and Heat Sink Requirements
The value for RQJA is calculated using equation (3) and the
result can be substituted in equation (1).
The CS5207-2 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.
RQJC is 1.6¡C/Watt for the CS5207-2. For a high current
regulator such as the CS5207-2 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
The case is connected to VOUT on the CS5207-2, 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.
The maximum power dissipation for a regulator is:
4
CS5207-2
Package Specification
PACKAGE DIMENSIONS IN mm(INCHES)
PACKAGE THERMAL DATA
3L
TO-220
1.6
50
Thermal Data
RQJC
typ
RQJA
typ
ûC/W
ûC/W
3 Lead TO-220 (T) Straight
4.83 (.190)
4.06 (.160)
10.54 (.415)
9.78 (.385)
6.55 (.258)
5.94 (.234)
1.40 (.055)
1.14 (.045)
3.96 (.156)
3.71 (.146)
2.87 (.113)
2.62 (.103)
14.99 (.590)
14.22 (.560)
1.52 (.060)
1.14 (.045)
14.22 (.560)
13.72 (.540)
6.17 (.243) REF
1.40 (.055)
1.14 (.045)
1.02 (.040)
0.63 (.025)
0.56 (.022)
0.38 (.014)
2.79 (.110)
2.29 (.090)
5.33 (.210)
4.83 (.190)
2.92 (.115)
2.29 (.090)
Ordering Information
Part Number
CS5207-2GT3
Rev. 6/12/98
Type
7A, 1.5V output
Cherry Semiconductor Corporation reserves the right to
make changes to the specifications without notice. Please
contact Cherry Semiconductor Corporation for the latest
available information.
Description
3 L TO-220 Straight
5
© 1999 Cherry Semiconductor Corporation