CHERRY CS5253-1

CS5253-1
CS5253-1
3A 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
D2PAK 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.
VCONTROL
10mF
10V
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
VOUT
VPOWER VSENSE
Adjust
100mF
5V
■ VCONTROL Dropout < 1.05V @
5 Lead D2PAK
2.5V @ 3A
CS5253-1
3.3V
■ VPOWER Dropout < 0.40V @ 3A
Package Options
Applications Diagram
5.0V
■ 1.25V to 5V VOUT at 3A
0.1mF
5V
1
124
1%
1. VSENSE
2. Adjust
3. VOUT
300mF
5V
124 Load
1%
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. 5/6/99
1
A
¨
Company
CS5253-1
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
Lead Temperature Soldering
Reflow (SMD styles only) ......................................................................................60 sec. max above 183¡C, 230¡C peak
ESD Damage Threshold............................................................................................................................................................2kV
Electrical Characteristics: 0¡C²TA ² 70¡C, 0¡C²TJ ² 150¡C, VSENSE = VOUT and VAdj = 0V unless otherwise specified.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
1.237
(-1%)
1.250
1.263
(+1%)
V
Reference Voltage
VCONTROL=2.75V to 12V,
VPOWER=2.05V to 5.5V, IOUT = 10mA to 3A
Line Regulation
VCONTROL = 2.5V to 12V,
VPOWER = 1.75V to 5.5V, IOUT = 10mA
.02
.20
%
Load Regulation
VCONTROL = 2.75V,
VPOWER = 2.05V, IOUT = 10mA to 3A,
with remote sense
.04
.30
%
Minimum Load Current
(Note 1)
VCONTROL = 5V, VPOWER = 3.3V,
ÆVOUT = +1%
5
10
mA
Control Pin Current
(Note 2)
Adjust Pin Current
VCONTROL = 2.75V, VPOWER = 2.05V, IOUT = 100mA
VCONTROL = 2.75V, VPOWER = 2.05V, IOUT = 3A
VCONTROL =2.75V, VPOWER = 2.05V, IOUT = 10mA
6
35
60
10
120
120
mA
mA
µA
Current Limit
VCONTROL = 2.75V, VPOWER = 2.05V,
ÆVOUT = -1%
3.1
4.0
A
Short Circuit Current
VCONTROL = 2.75V, VPOWER = 2.05V, VOUT = 0V
2.6
3.5
A
Ripple Rejection
(Note 3)
VCONTROL = VPOWER = 3.25V,
VRIPPLE = [email protected],
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 = 2.05V, IOUT = 100mA
VPOWER = 2.05V, IOUT = 1A
VPOWER = 2.05V, IOUT = 3A
0.90
1.00
1.05
1.15
1.15
1.30
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 = 3A
.05
.15
.40
.15
.25
.60
V
V
V
RMS Output Noise
Freq = 10Hz to 10kHz, TA = 25¡C
0.003
Temperature Stability
0.5
Thermal Shutdown (Note 5)
150
Thermal Shutdown Hysteresis
VCONTROL = 13V, VPOWER not connected,
VADJUST = VOUT = VSENSE = 0V
VPOWER Supply Only
Output Current
VPOWER = 6V, VCONTROL not connected,
VADJUST = VOUT = VSENSE = 0V
Note 2:
Note 3:
Note 4:
Note 5:
%
180
210
¡C
50
mA
1.0
mA
25
VCONTROL Supply Only
Output Current
Note 1:
%VOUT
0.1
¡C
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 VCONTROL 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 the minimum control voltage, (VCONTROL) or minimum power voltage (VPOWER) to output voltage differential
required to maintain 1% 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.
2
CS5253-1
Package Pin Description
PACKAGE PIN #
PIN SYMBOL
FUNCTION
5Lead D2 PAK
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% bandgap reference voltage and carries a bias current of
about 50µA. 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 3A of
current.
4
VCONTROL
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.
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 0.6V greater
than the output voltage, depending on output current. The output load current of 3A is supplied through this pin.
Block Diagram
VPOWER
VCONTROL
BIAS
and
TSD
VREF
+
EA
IA
+
-
VOUT
VSENSE
Adjust
3
CS5253-1
Typical Performance Characteristics
Load Regulation vs Output Current
1.253
0.12
1.252
0.10
Load Regulation (%)
Reference Voltage (V)
Reference Voltage vs Junction Temperature
1.251
1.250
1.249
1.248
0.08
TJ = 120°C
0.06
TJ = 20°C
0.04
TJ = 0°C
0.02
1.247
0
20
40
60
80
100
0
120
0
0.5
1.0
Junction Temperature (C)
1.5
2.0
2.5
3.0
Output Current (A)
Transient Response
Output Current vs VPOWER-VOUT
5.0
VCONTROL = 5.0V
VPOWER = 3.3V
VOUT = 2.5V
CCONTROL = 10mF
CPOWER = 100mF
CADJ = 0.1mF
COUT = 300mF
Measured at
DVOUT = -1%
4.5
4.0
Output Current (A)
3.5
VOUT
3.0
2.5
2.0
1.5
1.0
ILOAD,
10mA to 3A
0.5
0
0
1
2
3
4
5
6
VPOWER - VOUT (V)
Minimum Load Current vs VCONTROL-VOUT
Adjust Pin Current vs Junction Temperature
85
1200
VPOWER =3.3V
D VOUT=+1%
1150
Minimum Load Current (mA)
IADJ (mA)
80
75
70
65
1100
1050
1000
950
900
850
60
800
0
20
40
60
80
100
120
140
Junction Temperature (C)
4
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
CS5253-1
Typical Performance Characteristics
Short Circuit Output Current vs Junction Temperature
Ripple Rejection vs Frequency
90.0
VCONTROL = 2.75V
VPOWER = 2.05V
80.0
3.8
Ripple Rejection (dB)
Short Circuit Output Current Limit (A)
3.9
3.7
3.6
3.5
70.0
60.0
50.0
40.00
VIN-VOUT=2V
IOUT=4A
VRIPPLE=1VP-P
COUT=22mF
CADJ=0.1mF
30.0
3.4
20.0
10.0
3.3
0
20
40
60
80
100
120
101
140
102
103
Junction Temperature (C)
105
104
106
Frequency (Hz)
VCONTROL Only Output Current vs Junction Temperature
VCONTROL Dropout Voltage vs Output Current
12
1100
Vcontrol Dropout Voltage (mV)
VCONTROL = 13V,
VOUT = 0V,
Vpower not connected
10
8
Iout (mA)
6
4
2
TJ = 0°C
1000
TJ = 20°C
TJ = 120°C
900
VPOWER = 2.05V
0
0
20
40
60
80
100
120
800
140
0.0
0.5
VPOWER Dropout Voltage vs Output Current
2.0
2.5
3.0
916.4
VCONTROL =5V
D VOUT=+1%
916.3
450
400
Minimum Load Current (mA)
Vpower Dropout Voltage (V)
1.5
Minimum Load Current vs VPOWER-VOUT
500
TJ = 120°C
350
TJ = 20°C
300
TJ = 0°C
250
200
150
916.2
916.1
916.0
915.9
915.8
915.7
915.6
915.5
50
0
1.0
Output Current (A)
Junction Temperature (C)
915.4
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Output Current (A)
5
0.50
1.50
2.50
VPOWER-VOUT (V)
3.50
4.50
VPOWER Only Output Current vs Junction Temperature
VCONTROL Supply Current vs Junction Temperature
40
30
VCONTROL = 2.75V
VPOWER = 2.05V
35
VPOWER = 6V
VOUT = 0V
VCONTROL not connected
25
30
ICONTROL (mA)
20
IOUT (uA)
CS5253-1
Typical Performance Characteristics: Continued
15
10
IOUT = 3A
25
20
15
10
IOUT = 1A
5
5
0
0
20
40
60
80
100
120
0
140
IOUT = 100mA
0
20
40
60
80
100
120
140
Junction Temperature (C)
Junction Temperature (C)
Theory of Operation
Design Guidelines
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.
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 R1 and R2 causes a fixed current
to flow to ground. This current creates a voltage across R2
that adds to the 1.260V 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:
VPOWER Function
The CS5253-1 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 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 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.
VOUT = 1.260V ´
R1+R2
R1
+ R2 ´ IADJ
The term IADJ ´ 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 of the same composition for best tracking over temperature. The divider resistors should be placed physically as close to the load as possible.
VCONTROL
5V
VOUT
CS5253-1
Output Voltage Sensing
The CS5253-1 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.
3.3V
2.5V
@3A
VPOWER VSENSE
Adjust
R1
R2
Figure 1: Typical application schematic. The resistor divider sets VOUT,
with the internal 1.260V reference dropped across R1.
6
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
VPOWER 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 VPOWERVOUT 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 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.
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
VCONTROL 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.
External Supply
External
Supply
VControl
VSENSE
VPower
VAdjust
VCONTROL VOUT
VOUT
CS5253-1
VPOWER VSENSE
Adjust
Figure 2: This circuit is an example of how the CS5253-1 can be shortcircuit-protected when operating with VOUT > 6V.
Figure 3: Diode protection circuit.
7
CS5253-1
Application Notes: continued
CS5253-1
Application Notes: continued
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
,
T
where
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)
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:
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.
RQJA = RQJC + RQCS + RQSA
The value for RQJC is 2.5ûC/watt for the CS5253-1 in the D2
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 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 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 VOUT 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
8
CS5253-1
Package Specification
PACKAGE DIMENSIONS IN mm (INCHES)
PACKAGE THERMAL DATA
Thermal Data
RQJC
RQJA
typ
typ
5Lead
D2PAK
2.5
10-50*
ûC/W
ûC/W
*Depending on thermal properties of substrate. RQJA = RQJC + RQCA
5 Lead D2PAK (DP)
10.31 (.406)
10.05 (.396)
1.40 (.055)
1.14 (.045)
1.68 (.066)
1.40 (.055)
8.53 (.336)
8.28 (.326)
15.75 (.620)
14.73 (.580)
2.74(.108)
2.49(.098)
0.91 (.036)
0.66 (.026)
2.79 (.110)
2.29 (.090)
1.70 (.067) REF
.254 (.010) REF
0.10 (.004)
0.00 (.000)
4.57 (.180)
4.31 (.170)
Ordering Information
Part Number
CS5253-1GDP5
CS5253-1GDPR5
Rev. 5/6/99
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
5 Lead D2PAK
5 Lead D2PAK (tape & reel)
9
© 1999 Cherry Semiconductor Corporation