CHERRY CS5258-1GT5

CS5258-1
CS5258-1
8A LDO 5-Pin Adjustable Linear Regulator
Features
Description
This new very low dropout regulator is designed to power the next
generation of advanced microprocessors. To achieve very low dropout,
the internal pass transistor is powered separately from the control circuitry. Furthermore, with the control
and power inputs tied together, this
device can be used in single supply
configuration and still offer a better
dropout voltage than conventional
PNP-NPN based LDO regulators. In
this mode the dropout is determined
by the minimum control voltage.
It is supplied in a five-terminal TO220 package, which allows for the
implementation of a remote-sense
pin permitting very accurate regulation of output voltage directly at the
load, where it counts, rather than at
the regulator. This remote sensing
feature virtually eliminates output
voltage variations due to load
changes and resistive voltage drops.
Typical load regulation measured at
the sense pin is 1mV for an output
voltage of 2.5V with a load step of
10mA to 8A.
The very fast transient loop response
easily meets the needs of the latest
microprocessors. In addition, a small
capacitor on the Adjust pin will further improve the transient capabilities.
Internal protection circuitry provides for Òbust-proofÓ operation,
similar to three-terminal regulators.
This circuitry, which includes overcurrent, short circuit, supply
sequencing and overtemperature
protection, will self protect the regulator under all fault conditions.
The CS5258-1 is ideal for generating
a secondary 2 - 2.5V low voltage
supply on a motherboard where
both 5V and 3.3V are already
available.
8A
■ 1.5% Trimmed Reference
■ Fast Transient Response
■ Remote Voltage Sensing
■ Thermal Shutdown
■ Current Limit
■ Short Circuit Protection
■ Backwards Compatible with
3-pin Regulators
VCONTROL VOUT
[email protected]
VPOWER VSENSE
Adjust
10mF
10V
■ VCONTROL Dropout <1.15V @
5 Lead TO-220
CS5258-1
3.3V
■ VPOWER Dropout <0.4V @ 8A
Package Options
Applications Diagram
5.0V
■ 1.25V to 5V VOUT at 8A
100mF
5V
0.1mF
5V
124
1%
124 Load
1%
300mF
5V
1. VSENSE
1
2. Adjust
3. VOUT
4. VCONTROL
5. VPOWER
Tab = VOUT
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. 3/17/99
1
A
¨
Company
CS5258-1
Absolute Maximum Ratings
VPOWER Input Voltage .................................................................................................................................................................6V
VCONTROL Input Voltage ...........................................................................................................................................................13V
Operating Junction Temperature Range...........................................................................................................0¡C ² TJ ² 150¡C
Storage Temperature Range ................................................................................................................................-65¡C to +150¡C
ESD Damage Threshold............................................................................................................................................................2kV
Lead Temperature Soldering
Wave Solder (through hole styles only) .....................................................................................10 sec. max, 260¡C peak
Electrical Characteristics: 0¡C ² TA ² 70¡C, 0¡C ² TJ ² 150¡C, VSENSE = VOUT and VAdj = 0V unless otherwise specified.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
1.253
1.272
(+1.5%)
V
Reference Voltage
VCONTROL = 2.75V to 12V, VPOWER = 2.15V to 5.5V, 1.234
10mA ² IOUT ² 8A
(-1.5%)
Line Regulation
VCONTROL = 2.5V to 12V, VPOWER = 1.75V to 5.5V,
IOUT = 10mA
.02
.20
%
Load Regulation
(Note 3)
VCONTROL = 2.75V, VPOWER = 2.15V,
IOUT = 10mA to 8A, with remote sense
.04
.20
%
Minimum Load Current
(Note 1)
VCONTROL = 5V, VPOWER = 3.3V, ÆVOUT= +1%
5
10
mA
Control Pin Current
(Note 2)
VCONTROL = 2.75V, VPOWER = 2.15V, IOUT = 100mA
VCONTROL = 2.75V, VPOWER = 2.15V, IOUT = 4A
VCONTROL = 2.75V, VPOWER = 1.75V, IOUT = 4A
VCONTROL = 2.75V, VPOWER = 2.15V, IOUT = 8A
6
30
33
80
10
60
70
180
mA
mA
mA
mA
Adjust Pin Current
VCONTROL = 2.75V, VPOWER = 2.15V, IOUT = 10mA
60
120
µA
Current Limit
VCONTROL = 2.75V, VPOWER = 2.15V, ÆVOUT= -1.5%
8.1
10.0
A
Short Circuit Current
VCONTROL = 2.75V, VPOWER = 2.15V, VOUT = 0V
6.0
9.0
A
Ripple Rejection
(Note 3)
VCONTROL = VPOWER = 3.25V Avg,
VRipple = 1VP-P @ 120Hz, IOUT = 4A, CADJ = 0.1µF
60
80
dB
Thermal Regulation
30ms Pulse, TA = 25¡C
0.002
%/W
VCONTROL Dropout Voltage
(Minimum VCONTROL-VOUT)
(Note 4)
VPOWER = 2.15V, IOUT = 100mA
VPOWER = 2.15V, IOUT = 1A
VPOWER = 2.15V, IOUT = 2.75A
VPOWER = 2.15V, IOUT = 4A
VPOWER = 2.15V, IOUT = 8A
1.00
1.00
1.00
1.00
1.15
1.15
1.15
1.15
1.15
1.30
V
V
V
V
V
VPOWER Dropout Voltage
(Minimum VPOWER-VOUT)
(Note 4)
VCONTROL = 2.75V, IOUT = 100mA
VCONTROL = 2.75V, IOUT = 1A
VCONTROL = 2.75V, IOUT = 2.75A
VCONTROL = 2.75V, IOUT = 4A
VCONTROL = 2.75V, IOUT = 8A
.10
.15
.20
.26
.40
.15
.20
.30
.40
.70
V
V
V
V
V
RMS Output Noise
Freq = 10Hz to 10kHz, TA = 25¡C
0.003
%VOUT
0.5
%
Temperature Stability
Thermal Shutdown (Note 5)
150
Thermal Shutdown Hysteresis
VCONTROL Supply Only
Output Current
180
210
25
VCONTROL = 13V, VPOWER not connected,
VADJUST = VOUT = VSENSE = 0V
2
¡C
¡C
50
mA
PARAMETER
TEST CONDITIONS
VPOWER Supply Only
Output Current
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
MIN
VPOWER = 6V, VCONTROL not connected,
VADJUST = VOUT = VSENSE = 0V
TYP
MAX
UNIT
0.1
1
mA
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 current requirement.
The control pin current is the drive current required for the output transistor. This current will track output
current with roughly a 1:100 ratio. The minimum value is equal to the quiescent current of the device.
This parameter is guaranteed by design and is not 100% production tested.
Dropout is defined as either minimum control voltage (VCONTROL) or minimum power voltage (VPOWER) to output voltage differential required to maintain 1.5% regulation at a particular load current.
This parameter is guaranteed by design, but not parametrically tested in production. However, a 100% thermal shutdown
functional test is performed on each part.
Package Pin Description
PACKAGE PIN #
PIN SYMBOL
FUNCTION
5L TO-220
1
VSENSE
This Kelvin sense pin allows for remote sensing of the output voltage at the
load for improved regulation. It is internally connected to the positive input of
the voltage sensing error amplifier.
2
Adjust
This pin is connected to the low side of the internally trimmed 1.5% bandgap
reference voltage and carries a bias current of about 50uA. A resistor divider
from Adj to VOUT and from Adj to ground sets the output voltage. Also, transient response can be improved by adding a small bypass capacitor from this
pin to ground.
3
VOUT
This pin is connected to the emitter of the power pass transistor and provides
a regulated voltage capable of sourcing 8A of current.
4
VCONTROL
This is the supply voltage for the regulator control circuitry. For the device to
regulate, this voltage should be between 1V and 1.30V (depending on the output current) greater than the output voltage. The control pin current will be
about 1% of the output current .
5
VPOWER
This is the power input voltage. The pin is physically connected to the collector of the power pass transistor. For the device to regulate, this voltage should
be between 0.1V and .7V greater than the output voltage depending on output
current. The output load current of 8A is supplied through this pin.
Block Diagram
VPOWER
VCONTROL
BIAS
and
TSD
VREF
+
EA
IA
+
-
VOUT
VSENSE
Adjust
3
CS5258-1
Electrical Characteristics: 0¡C ² TA ² 70¡C, 0¡C ² TJ ² 150¡C, VSENSE = VOUT and VAdj = 0V unless otherwise specified.
CS5258-1
Typical Performance Characteristics
Load Regulation vs Output Current
0.100
0.100
0.075
0.090
0.050
0.080
Output Voltage Deviation (%)
Ooutput Voltage Deviation (%)
Reference Voltage vs Temperature
0.025
-0.000
-0.025
-0.050
I0=10mA
VCONTROL=2.75V, VPOWER=2.15V
-0.075
-0.100
-0.125
VPOWER=2.15V
VCONTROL=2.75V
0.070
0.060
0.050
0.040
0.030
0.020
0.010
0.000
0.00
-0.150
0 10 20 30
40
50 60 70 80
1.00
90 100 110 120 130
2.00
3.00
4.00
5.00
6.00
7.00
8.00
Output Current (A)
TJ (°C)
Ripple Rejection vs Frequency
83.0
90.0
81.0
80.0
79.0
Ripple Rejection (dB)
Adjust Pin Current (mA)
Adjust Pin Current vs Temperature
77.0
75.0
73.0
71.0
70.0
60.0
50.0
40.00
VIN-VOUT=2V
IOUT=4A
VRIPPLE=1VP-P
COUT=22mF
CADJ=0.1mF
30.0
69.0
20.0
67.0
10.0
65.0
0.0
20.0
40.0
60.0
80.0
100.0
120.0
101
140.0 160.0
102
Temperature (C)
1.250
VCONTROL =2.75V
VCONTROL Drop Out Voltage (V)
VPOWER Dropout Voltage (V)
0.800
0.700
0.600
0.500
0.400
0.300
0.200
0.100
0.000
1.00
2.00
3.00
4.00
5.00
106
VCONTROL Dropout vs IOUT
1.000
0.00
105
104
Frequency (Hz)
VPOWER Dropout Voltage vs IOUT
0.900
103
6.00
7.00
VPOWER=2.15V
1.000
0.750
0.500
0.250
0.00
8.00
0.00
Output Current (A)
1.00
2.00
3.00
4.00
5.00
Output Current (A)
4
6.00
7.00
8.00
CS5258-1
Typical Performance Characteristics: continued
Minimum Load Current vs VCONTROL-VOUT
Current Step Transient Response
VPOWER = 3.3V
D VOUT= +1%
1150.000
1100.000
1050.000
1000.000
950.000
100
50
0
COUT=330mF
CPOWER=110mF
CCONTROL=10mF
CADJUST=0.1mF
VCONTROL=5V
VPOWER=3.3V
VOUT=2.5V
-50
-100
900.000
850.000
800.000
1.0 2.0
3.0
4.0
5.0
6.0
7.0 8.0
VCONTROL-VOUT (V)
9.0
8
Current (A)
Minimum Load Current (mA)
Output Voltage Deviation (mV)
1200.000
10.0 11.0
0
0
0
1
2
3
5
4
Time (ms)
Adjust Pin Current vs Output Current
15.0
14.0
13.0
12.0
11.0
10.0
9.0
77.00
V POWER =2.15
V CONTROL =2.75V
Adjust Pin Current (mA)
Output Current (A)
Short Circuit Current vs VPOWER-VOUT
8.0
7.0
6.0
5.0
4.0
76.00
75.00
74.00
73.00
3.0
2.0
1.0
0.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
72.00
5.5
0.00
VPOWER-VOUT (V)
Adjust Pin Current vs VCONTROL-VOUT
2.00
3.00 4.00
5.00
Output Current (A)
6.00
7.00
8.00
Adjust Pin Current vs VPOWER-VOUT
75.00
75.00
VPOWER =2.15V
IL=10mA
VCONTROL=2.75V
IL=10mA
74.00
74.00
Adjust Pin Current (mA)
Adjust Pin Current (mA)
1.00
73.00
72.00
71.00
73.00
72.00
71.00
70.00
70.00
1.0
2.0
3.0
4.0
5.0
6.0
7.0 8.0
VCONTROL-VOUT (V)
9.0
10.0 11.0
0.50
5
1.50
2.50
VPOWER-VOUT (V)
3.50
4.50
CS5258-1
Typical Performance Characteristics: continued
Minimum Load Current vs VPOWER-VOUT
916.400
VCONTROL = 5V
D VOUT = +1%
Minimum Load Current (mA)
916.300
916.200
916.100
916.000
915.900
915.800
915.700
915.600
915.500
915.400
0.50
1.50
2.50
VPOWER-VOUT (V)
3.50
4.50
Application Notes
Theory of Operation
Design Guidelines
The CS5258-1 linear regulator provides adjustable voltages
from 1.25V to 5V at currents up to 8A. The regulator is protected against short circuits, and includes a thermal shutdown circuit with hysteresis. The output, which is current
limited, consists of a PNP-NPN transistor pair and requires
an output capacitor for stability. A detailed procedure for
selecting this capacitor is included in the Stability
Considerations section.
Adjustable Operation
This LDO adjustable regulator has an output voltage range
of 1.25V to 5V. An external resistor divider sets the output
voltage as shown in Figure 1. The regulatorÕs voltage sensing error amplifier maintains a fixed 1.253V 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 1.253V across R1 and sets the
overall output voltage. The adjust pin current (typically
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:
R1+R2
VOUT = 1.253V ´
+ R2 ´ IADJ
R1
VPOWER Function
The CS5258-1 utilizes a two supply approach to maximize
efficiency. The collector of the power device is brought out
to the VPOWER pin to minimize internal power dissipation
under high current loads. VCONTROL provides power for
the control circuitry and the drive for the output NPN
transistor. VCONTROL should be at least 1V greater than the
output voltage. Special care has been taken to ensure that
there are no supply sequencing problems. The output voltage will not turn on until both supplies are operating. If
the control voltage comes up first, the output current will
be typically limited to about 3mA until the power input
voltage comes up. If the power input voltage comes up
first the output will not turn on at all until the control voltage comes up. The output can never come up unregulated.
The CS5258-1 can also be used as a single supply device
with the control and power inputs tied together. In this
mode, the dropout will be determined by the minimum
control voltage.
(
)
The term IADJ ´ R2 represents the error added by the adjust
pin current.
R1 is chosen so that the minimum load current is a least
10mA. R1 and R2 should be of the same composition for
best tracking over temperature. The divider resistors
should be located as close to the load as possible.
VCONTROL
VOUT
CS5258-1
VPOWER VSENSE
Adjust
R1
Output Voltage Sensing
The CS5258-1 five terminal linear regulator includes a dedicated VSENSE function. This allows for true Kelvin sensing
of the output voltage. This feature can virtually eliminate
errors in the output voltage due to load regulation.
Regulation will be optimized at the point where the sense
pin is tied to the output.
R2
Figure 1: An external resistor divider sets the value of VOUT. The 1.253V
reference voltage drops across R1.
6
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 manufacturerÕs data sheet provides this information.
A 300µF tantalum capacitor will work for most applications, but with high current regulators such as the
CS5258-1 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:
While not required, a bypass capacitor connected between
the adjust pin and ground will improve transient response
and ripple rejection. A 0.1µF tantalum capacitor is recommended for Òfirst cutÓ design. Value and type may be varied to optimize performance vs. price.
Other Adjustable Operation Considerations
The CS5258-1 linear regulator has an absolute maximum
specification of 6V for the voltage difference between VIN
and VOUT. However, the IC may be used to regulate voltages in excess of 6V. The two main considerations in such a
design are the sequencing of power supplies and short circuit capability.
Power supply sequencing should be such that the VCONTROL supply is brought up coincidentally with or before the
VPOWER supply. This allows the IC to begin charging the
output capacitor as soon as the VPOWER to VOUT differential
is large enough that the pass transistor conducts. As VPOWER increases, the pass transistor will remain in dropout, and
current is passed to the load until VOUT is in regulation.
Further increase in the supply voltage brings the pass transistor out of dropout. In this manner, any output voltage
less than 13V may be regulated, provided the VPOWER to
VOUT differential is less than 6V. In the case where VCONTROL and VPOWER are shorted, there is no theoretical limit to
the regulated voltage as long as the VPOWER to VOUT differential of 6V is not exceeded.
There is a possibility of damaging the IC when VPOWER-VIN
is greater than 6V if a short circuit occurs. 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 circuitry can
become active. Additional circuitry may be required to
clamp the VPOWER to VOUT differential to less than 6V if fail
safe 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.
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 transient load conditions. The output capacitor network should be as close to the load as possible 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 VCONTROL
drops. In the CS5258-1 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. Use of
the diode has the added benefit of bleeding VOUT to
ground if VCONTROL is shorted. This prevents an unregulated output from causing system damage.
External Supply
VCONTROL
VControl
VSENSE
VPower
VAdjust
VOUT
CS5258-1
VPOWER VSENSE
Adjust
VOUT
Figure 2: Example clamp circuitry for VPOWER - VOUT > 6V.
Figure 3: Diode protection against VCONTROL short circuit conditions.
Stability Considerations
The output compensation capacitor helps determine three
main characteristics of a linear regulator: start-up delay,
load transient response, and loop stability.
7
CS5258-1
Application Notes: continued
CS5258-1
Application Notes: continued
applications. Also, as with all high power packages, thermal compound is necessary to ensure proper heat flow. For
added safety, this high current LDO includes an internal
thermal shutdown circuit
The thermal characteristics of an IC depend on the following four factors: junction temperature, ambient temperature, die power dissipation, and the thermal resistance
from the die junction to ambient air. The maximum junction temperature can be determined by:
A rule of thumb useful in determining if a protection diode
is required is to solve for current
I= C ´ V , where
T
I is the current flow out of the load capacitance
when VCONTROL is shorted,
C is the value of load capacitance
V is the output voltage, and
T is the time duration required for VCONTROL
to transition from high to being shorted.
If the calculated current is greater than or equal to the typical short circuit current value provided in the specifications, serious thought should be given to the use of a protection diode.
TJ(max) = TA(max) + PD(max) ´ RQJA
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:
PD(max) = (VIN(max) -VOUT(min))IOUT(max) + VIN(max)*IIN(max)
Current Limit
The internal current limit circuit limits the output current
under excessive load conditions.
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 which is measured in degrees per watt.
Like series electrical resistances, these thermal resistances
are summed to determine the total thermal resistance
between the die junction and the surrounding air, RQJA.
This total thermal resistance is comprised of three components. These resistive terms are measured from junction to
case (RQJC), case to heat sink RQCS), and heat sink to ambient air (RQSA). The equation is:
Short Circuit Protection
The device includes short circuit protection circuitry that
clamps the output current at approximately two amperes
less than its current limit value. This provides for a current
foldback function, which reduces power dissipation even
further under a direct shorted load.
Thermal Shutdown
The thermal shutdown circuitry is guaranteed by design to
activate above a die junction temperature of approximately
150¡C and to shut down the regulator output. This circuitry has 25¡C of typical hysteresis, thereby allowing the regulator to recover from a thermal fault automatically.
RQJA = RQJC + RQCS + RQSA
The value for RQJC is 1.4ûC watt for the CS5258-1 in the
TO-220 package. For a high current regulator such as the
CS5258-1 the majority of heat is generated in the power
transistor section. The value for RQSA depends on the heat
sink type, while the 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 our Cherry application note
ÒThermal Management for Linear Regulators.Ó
Calculating Power Dissipation and Heat Sink
Requirements
High power regulators such as the CS5258-1 family usually
operate at high junction temperatures. Therefore, it is
important to calculate the power dissipation and junction
temperatures accurately to ensure that an adequate heat
sink is used. Since the package tab is connected to VOUT on
the CS5258-1, electrical isolation may be required for some
8
CS5258-1
CS
Package Specification
PACKAGE DIMENSIONS IN mm (INCHES)
PACKAGE THERMAL DATA
Thermal Data
RQJC
RQJA
5L
TO-220
1.4
50
typ
typ
ûC/W
ûC/W
5 Lead TO-220 (T) Straight
10.54 (.415)
9.78 (.385)
2.87 (.113)
6.55 (.258) 2.62 (.103)
5.94 (.234)
4.83 (.190)
4.06 (.160)
1.40 (.055)
1.14 (.045)
3.96 (.156)
3.71 (.146)
14.99 (.590)
14.22 (.560)
14.22 (.560)
13.72 (.540)
1.02 (.040)
0.76 (.030)
1.83(.072)
1.57(.062)
1.02(.040)
0.63(.025)
6.93(.273)
6.68(.263)
2.92 (.115)
2.29 (.090)
Cherry Semiconductor Corporation reserves the right to
make changes to the specifications without notice. Please
contact Cherry Semiconductor Corporation for the latest
available information.
Ordering Information
Part Number
CS5258-1GT5
Rev. 3/17/99
0.56 (.022)
0.36 (.014)
Description
5L TO-220 Straight
9
© 1999 Cherry Semiconductor Corporation