Page 1
Features
Package Options
CS5253-1
3A LDO 5-Pin Adjustable Linear Regulator
CS5253-1
Description
Applications Diagram
1
5 Lead D2PAK
1
1. V
SENSE
2. Adjust
3. V
OUT
4. V
CONTROL
5. V
POWER
Tab = V
OUT
Rev. 5/6/99
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
¨
V
SENSE
V
OUT
V
CONTROL
V
POWER
CS5253-1
2.5V @ 3A
300mF
5V
Load
124
1%
124
1%
0.1mF
5V
100mF
5V
10mF
10V
3.3V
5.0V
Adjust
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
D
2
PAK package, which allows for
the implementation of a remotesense 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 resis-
tive voltage drops. Typical load
regulation measured at the sense
pin is less than 1mV for an output
voltage of 2.5V with a load step of
10mA to 3A.
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, and over-temperature protection will self protect
the regulator under all fault conditions.
The CS5253-1 is ideal for generating
a secondary 2-2.5V low voltage
supply on a motherboard where
both 5V and 3.3V are already available.
■ 1.25V to 5V V
OUT
at 3A
■ V
POWER
Dropout < 0.40V @ 3A
■ V
CONTROL
Dropout < 1.05V @
3A
■ 1% Trimmed Reference
■ Fast Transient Response
■ Remote Voltage Sensing
■ Thermal Shutdown
■ Current Limit
■ Short Circuit Protection
■ Drop-In Replacement for
Semtech EZ1582
■ Backwards Compatible with
3-pin Regulators
Page 2
Electrical Characteristics:
0¡C²TA² 70¡C, 0¡C²TJ² 150¡C, V
SENSE
= V
OUT
and V
Adj
=
0V unless otherwise specified.
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
CS5253-1
2
Absolute Maximum Ratings
V
POWER
Input Voltage.......................................................................................................................................................................6V
V
CONTROL
Input Voltage.................................................................................................................................................................13V
Operating Junction Temperature Range ................................................................................................................0¡C ² T
J
² 150¡C
Storage Temperature Range .....................................................................................................................................-65¡C to +150¡C
Lead Temperature Soldering
Reflow (SMD styles only) ......................................................................................60 sec. max above 183¡C, 230¡C peak
ESD Damage Threshold............................................................................................................................................................2kV
Reference Voltage V
CONTROL
=2.75V to 12V, 1.237 1.250 1.263 V
V
POWER
=2.05V to 5.5V, I
OUT
= 10mA to 3A (-1%) (+1%)
Line Regulation V
CONTROL
= 2.5V to 12V, .02 .20 %
V
POWER
= 1.75V to 5.5V, I
OUT
= 10mA
Load Regulation V
CONTROL
= 2.75V, .04 .30 %
V
POWER
= 2.05V, I
OUT
= 10mA to 3A,
with remote sense
Minimum Load Current V
CONTROL
= 5V, V
POWER
= 3.3V, 5 10 mA
(Note 1) ÆV
OUT
= +1%
Control Pin Current V
CONTROL
= 2.75V, V
POWER
= 2.05V, I
OUT
= 100mA 6 10 mA
(Note 2) V
CONTROL
= 2.75V, V
POWER
= 2.05V, I
OUT
= 3A 35 120 mA
Adjust Pin Current V
CONTROL
=2.75V, V
POWER
= 2.05V, I
OUT
= 10mA 60 120 µA
Current Limit V
CONTROL
= 2.75V, V
POWER
= 2.05V, 3.1 4.0 A
ÆV
OUT
= -1%
Short Circuit Current V
CONTROL
= 2.75V, V
POWER
= 2.05V, V
OUT
= 0V 2.6 3.5 A
Ripple Rejection V
CONTROL
= V
POWER
= 3.25V, 60 80 dB
(Note 3) V
RIPPLE
= 1V
P-P
@120Hz,
I
OUT
= 4A, C
ADJ
= 0.1µF
Thermal Regulation 30ms Pulse, TA=25¡C 0.002 %/W
V
CONTROL
Dropout Voltage V
POWER
= 2.05V, I
OUT
= 100mA 0.90 1.15 V
(Minimum V
CONTROL-VOUT
)V
POWER
= 2.05V, I
OUT
= 1A 1.00 1.15 V
(Note 4) V
POWER
= 2.05V, I
OUT
= 3A 1.05 1.30 V
V
POWER
Dropout Voltage V
CONTROL
= 2.75V, I
OUT
= 100mA .05 .15 V
(Minimum V
POWER-VOUT
)V
CONTROL
= 2.75V, I
OUT
= 1A .15 .25 V
(Note 4) V
CONTROL
= 2.75V, I
OUT
= 3A .40 .60 V
RMS Output Noise Freq = 10Hz to 10kHz, TA = 25¡C 0.003 %V
OUT
Temperature Stability 0.5 %
Thermal Shutdown (Note 5) 150 180 210 ¡C
Thermal Shutdown Hysteresis 25 ¡C
V
CONTROL
Supply Only V
CONTROL
= 13V, V
POWER
not connected, 50 mA
Output Current V
ADJUST
= V
OUT
= V
SENSE
= 0V
V
POWER
Supply Only V
POWER
= 6V, V
CONTROL
not connected, 0.1 1.0 mA
Output Current V
ADJUST
= V
OUT
= V
SENSE
= 0V
Note 1: 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.
Note 2: The V
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.
Note 3: This parameter is guaranteed by design and is not 100% production tested.
Note 4: Dropout is defined as either the minimum control voltage, (V
CONTROL)
or minimum power voltage (V
POWER
) to output voltage differential
required to maintain 1% regulation at a particular load current.
Note 5: This parameter is guaranteed by design, but not parametrically tested in production. However, a 100% thermal shutdown functional test is
performed on each part.
Page 3
CS5253-1
Package Pin Description
PACKAGE PIN # PIN SYMBOL FUNCTION
3
Block Diagram
V
CONTROL
BIAS
and
TSD
V
REF
EA
IA
V
OUT
V
SENSE
Adjust
-
+
-
+
V
POWER
5Lead D2PAK
1V
SENSE
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% bandgap reference voltage and carries a bias current of
about 50µA. A resistor divider from Adj to V
OUT
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.
3V
OUT
This pin is connected to the emitter of the power pass transistor
and provides a regulated voltage capable of sourcing 3A of
current.
4V
CONTROL
This is the supply voltage for the regulator control circuitry. For
the device to regulate, this voltage should be between 0.9V and
1.3V (depending on the output current) greater than the
output voltage. The control pin current will be about 1% of the
output current.
5V
POWER
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 0.6V greater
than the output voltage, depending on output current. The output load current of 3A is supplied through this pin.
Page 4
CS5253-1
4
Typical Performance Characteristics
0 20 40 60 80 100 120
Reference Voltage (V)
Junction Temperature (C)
1.247
1.248
1.249
1.250
1.251
1.252
1.253
Reference Voltage vs Junction Temperature
V
OUT
I
LOAD
,
10mA to 3A
V
CONTROL
= 5.0V
V
POWER
= 3.3V
V
OUT
= 2.5V
C
CONTROL
= 10mF
C
POWER
= 100mF
C
ADJ
= 0.1mF
C
OUT
= 300mF
Transient Response
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
01 23456
V
POWER
- V
OUT
(V)
Output Current (A)
Measured at
DV
OUT
= -1%
Output Current vs V
POWER-VOUT
I
ADJ
(mA)
Junction Temperature (C)
0
20
40 60
80 100 120 140
60
65
70
75
80
85
Adjust Pin Current vs Junction Temperature
1.0 3.0 4.0 5.0 6.0 7.0
800
Minimum Load Current (mA)
V
CONTROL-VOUT
(V)
9.0 10.0 11.02.0 8.0
850
900
950
1000
1050
1100
1150
1200
VPOWER =3.3V
D VOUT=+1%
Minimum Load Current vs V
CONTROL-VOUT
0.5 1.0 1.5 2.0 2.5
Output Current (A)
TJ = 120°C
T
J
= 20°C
0
3.0
0.08
0.10
0.12
0
0.02
0.04
0.06
Load Regulation (%)
TJ = 0°C
Load Regulation vs Output Current
Page 5
CS5253-1
5
Typical Performance Characteristics
10.0
10
1
Frequency (Hz)
Ripple Rejection (dB)
20.0
30.0
40.00
60.0
70.0
80.0
90.0
10
2
10
3
10
4
10
6
10
5
50.0
VIN-V
OUT
=2V
I
OUT
=4A
V
RIPPLE
=1V
P-P
C
OUT
=22mF
C
ADJ
=0.1mF
Ripple Rejection vs Frequency
Short Circuit Output Current Limit (A)
3.3
3.4
3.5
3.6
3.7
3.8
3.9
0 20 40 60 80 100 120 140
Junction Temperature (C)
V
POWER
= 2.05V
V
CONTROL
= 2.75V
Short Circuit Output Current vs Junction Temperature
Vpower Dropout Voltage (V)
0
0.0
Output Current (A)
50
150
200
250
300
350
400
450
500
0.5 1.0 3.02.52.01.5
TJ = 120°C
T
J
= 20°C
T
J
= 0°C
V
POWER
Dropout Voltage vs Output Current
0
2
4
6
8
10
12
0 20 40 60 80 100 120 140
Junction Temperature (C)
Iout (mA)
V
CONTROL
= 13V,
V
OUT
= 0V,
Vpower not connected
Vcontrol Dropout Voltage (mV)
0.0
Output Current (A)
800
900
1000
1100
0.5 1.0 3.02.52.01.5
TJ = 120°C
TJ = 20°C
TJ = 0°C
V
POWER
= 2.05V
V
CONTROL
Dropout Voltage vs Output CurrentV
CONTROL
Only Output Current vs Junction Temperature
0.50 1.50 2.50
915.5
Minimum Load Current (mA)
V
POWER-VOUT
(V)
3.50 4.50
915.6
915.7
915.8
915.9
916.0
916.1
916.2
916.4
VCONTROL =5V
D VOUT=+1%
915.4
916.3
Minimum Load Current vs V
POWER-VOUT
Page 6
CS5253-1
6
Typical Performance Characteristics: Continued
I
OUT
(uA)
0
5
10
15
20
25
30
0 20 40 60 80 100 120 140
Junction Temperature (C)
V
POWER
= 6V
V
OUT
= 0V
V
CONTROL
not connected
V
POWER
Only Output Current vs Junction Temperature
The CS5253-1 linear regulator provides adjustable voltages
from 1.26V to 5V at currents up to 3A. 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.
V
POWER
Function
The CS5253-1 utilizes a two supply approach to maximize
efficiency. The collector of the power device is brought out
to the V
POWER
pin to minimize internal power dissipation
under high current loads. V
CONTROL
provides for the control circuitry and the drive for the output NPN transistor.
V
CONTROL
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 limited to
about three milliamperes 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 CS5253-1 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.
Output Voltage Sensing
The CS5253-1 five terminal linear regulator includes a dedicated V
SENSE
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.
Adjustable Operation
This LDO adjustable regulator has an output voltage range
of 1.26V to 5V. An external resistor divider sets the output
voltage as shown in Figure 1. The regulatorÕs voltage sensing error amplifier maintains a fixed 1.260V reference
between the output pin and the adjust pin.
A resistor divider network R1and R2causes a fixed current
to flow to ground. This current creates a voltage across R
2
that adds to the 1.260V across R1and sets the overall output voltage. The adjust pin current (typically 50µA) also
flows through R2and adds a small error that should be
taken into account if precise adjustment of V
OUT
is neces-
sary. The output voltage is set according to the formula:
V
OUT
= 1.260V ´ + R2 ´ I
ADJ
The term I
ADJ
´ R2represents the error added by the adjust
pin current. R1is chosen so that the minimum load current
is at least 10mA. R1and R2should be of the same composition for best tracking over temperature. The divider resistors should be placed physically as close to the load as possible.
Figure 1: Typical application schematic. The resistor divider sets V
OUT
,
with the internal 1.260V reference dropped across R1.
R1+R
2
R
1
Design GuidelinesTheory of Operation
I
CONTROL
(mA)
40
0 20 40 60 80 100 120 140
Junction Temperature (C)
35
30
25
20
15
10
5
0
I
OUT
= 3A
I
OUT
= 1A
I
OUT
= 100mA
V
POWER
= 2.05V
V
CONTROL
= 2.75V
V
CONTROL
Supply Current vs Junction Temperature
5V
3.3V
V
CONTROL
V
POWER
CS5253-1
V
SENSE
Adjust
V
OUT
2.5V
@3A
R1
R2
Page 7
CS5253-1
7
Application Notes: continued
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 CS5253-1 linear regulator has an absolute maximum
specification of 6V for the voltage difference between
V
POWER
and V
OUT
. 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 V
CON-
TROL
supply is brought up coincidentally with or before the
V
POWER
supply. This allows the IC to begin charging the
output capacitor as soon as the V
POWER
to V
OUT
differential
is large enough that the pass transistor conducts. As V
POW-
ER
increases, the pass transistor will remain in dropout, and
current is passed to the load until V
OUT
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 V
POWER
to
V
OUT
differential is less than 6V. In the case where V
CON-
TROL
and V
POWER
are shorted, there is no theoretical limit
to the regulated voltage as long as the V
POWER
to V
OUT
dif-
ferential of 6V is not exceeded.
There is a possibility of damaging the IC when V
POWER
-
V
OUT
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. Overvoltage 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 V
POWER
to V
OUT
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.
Figure 2: This circuit is an example of how the CS5253-1 can be shortcircuit-protected when operating with V
OUT
> 6V.
Stability Considerations
The output 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 manufacturer's data sheet provides this
information.
A 300µF tantalum capacitor will work for most applications, but with high current regulators such as the
CS5253-1 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:
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
V
CONTROL
drops. In the CS5253-1 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.
Figure 3: Diode protection circuit.
External
Supply
External Supply
V
Control
V
Power
V
Adjust
V
SENSE
V
OUT
V
CONTROL
V
POWER
V
CS5253-1
V
SENSE
Adjust
OUT
Page 8
8
CS5253-1
Application Notes: continued
A rule of thumb useful in determining if a protection diode
is required is to solve for current:
I = ,
where
I is the current flow out of the load capacitance
when V
CONTROL
is shorted,
C is the value of load capacitance
V is the output voltage, and
T is the time duration required for V
CONTROL
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.
Current Limit
The internal current limit circuit limits the output current
under excessive load conditions.
Short Circuit Protection
The device includes short circuit protection circuitry that
clamps the output current at approximately 500mA less
than its current limit value. This provides for a current
foldback function, which reduces power dissipation 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.
Calculating Power Dissipation and Heat Sink
Requirements
High power regulators such as the CS5253-1 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 V
OUT
on the
CS5253-1, electrical isolation may be required for some
applications. Also, as with all high power packages, thermal compound in 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:
T
J(max)
= T
A(max)
+ PD
(max)
´ R
QJA
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)
= (V
IN(max)-VOUT(min))IOUT(max)
+ V
IN(max)
´ I
IN(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 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, R
QJA
.
This total thermal resistance is comprised of three components. These resistive terms are measured from junction to
case (R
QJC
), case to heat sink (R
QCS
), and heat sink to ambi-
ent air (R
QSA
). The equation is:
R
QJA
= R
QJC
+ R
QCS
+ R
QSA
The value for R
QJC
is 2.5ûC/watt for the CS5253-1 in the D
2
PAK package. For a high current regulator such as the
CS5253-1 the majority of heat is generated in the power
transistor section. The value for R
QSA
depends on the heat
sink type, while the R
QCS
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 R
QJA
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
C ´ V
T
Page 9
Ordering Information
9
Rev. 5/6/99
Thermal Data 5Lead
D2PAK
R
QJC
typ 2.5 ûC/W
R
QJA
typ 10-50* ûC/W
*Depending on thermal properties of substrate. R
QJA
= R
QJC
+ R
QCA
Package Specification
PACKAGE DIMENSIONS IN mm (INCHES)
PACKAGE THERMAL DATA
© 1999 Cherry Semiconductor Corporation
CS5253-1
Cherry Semiconductor Corporation reserves the right to
make changes to the specifications without notice. Please
contact Cherry Semiconductor Corporation for the latest
available information.
Part Number Description
CS5253-1GDP5 5 Lead D2PAK
CS5253-1GDPR5 5 Lead D2PAK (tape & reel)
5 Lead D2PAK (DP)
1.70 (.067) REF
0.10 (.004)
0.00 (.000)
10.31 (.406)
10.05 (.396)
0.91 (.036)
0.66 (.026)
1.40 (.055)
1.14 (.045)
4.57 (.180)
4.31 (.170)
1.68 (.066)
1.40 (.055)
2.74(.108)
2.49(.098)
.254 (.010) REF
2.79 (.110)
2.29 (.090)
15.75 (.620)
14.73 (.580)
8.53 (.336)
8.28 (.326)
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