CS5257A-1
CS5257A-1
7 LDO 5-Pin Adjustable Linear Regulator
A
Description
This new very low dropout regula-
tor is designed to power the next
generation of advanced micropro-
cessors. To achieve very low
dropout, the internal pass transistor
is powered separately from the con-
trol 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 mini-
mum control voltage.
It is supplied in five-terminal
TO-220 and D
2
PAK packages,
allowing for the implementation of
a remote-sense pin permitting very
accurate regulation of output volt-
age directly at the load, where it
counts, rather than at the regulator.
This remote sensing feature virtual-
ly eliminates output voltage varia-
tions due to load changes and resis-
tive 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
7A.
The very fast transient loop
response easily meets the needs of
the latest microprocessors. In addi-
tion, a small capacitor on the Adjust
pin will further improve the tran-
sient capabilities.
Internal protection circuitry pro-
vides for Òbust-proofÓ operation,
similar to three-terminal regulators.
This circuitry, which includes over-
current, short circuit, supply
sequencing and overtemperature
protection will self protect the regu-
lator under all fault conditions.
The CS5257A-1 is ideal for generat-
ing a secondary 2-2.5V low voltage
supply on a motherboard where
both 5V and 3.3V are already avail-
able.
Features
s
1.25V to 5V V
OUT
at 7A
s
V
POWER
Dropout < 0.35V @ 7A
s
V
CONTROL
Dropout < 1.10V @
7A
s
1.5% Trimmed Reference
s
Fast Transient Response
s
Remote Voltage Sensing
s
Thermal Shutdown
s
Current Limit
s
Short Circuit Protection
s
Drop-In Replacement for
LT1580
s
Backwards Compatible with
3-pin Regulators
Package Options
5 Lead D
2
PAK
5 Lead TO-220
Applications Diagram
5.0V
V
CONTROL
V
OUT
2.5V @ 7A
1
CS5257A-1
3.3V
V
POWER
V
SENSE
Adjust
100mF
5V
0.1mF
5V
124
1%
124 Load
1%
300mF
5V
1. V
SENSE
1
2. Adjust
3. V
OUT
4. V
CONTROL
5. V
POWER
Tab = V
OUT
10mF
10V
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
Rev. 4/5/99
1
A
¨
Company
CS5257A-1
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
Wave Solder (through hole styles only) .....................................................................................10 sec. max, 260¡C peak
Reflow (SMD styles only) ......................................................................................60 sec. max above 183¡C, 230¡C peak
ESD Damage Threshold............................................................................................................................................................2kV
Electrical Characteristics:
0¡C ² T
A
² 70¡C, 0¡C ² T
J
² 150¡C, V
SENSE
= V
OUT
and V
Adj
= 0V; unless otherwise specified.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Reference Voltage
Line Regulation
Load Regulation
(Note 3)
Minimum Load Current
(Note 1)
Control Pin Current
(Note 2)
V
CONTROL
= 2.75V to 12V, V
POWER
= 2.05V to 5.5V,
10mA ² I
OUT
² 7A
V
CONTROL
= 2.5V to 12V, V
POWER
= 1.75V to 5.5V,
I
OUT
= 10mA
V
CONTROL
= 2.75V, V
POWER
= 2.05V,
I
OUT
= 10mA to 7A, with remote sense
V
CONTROL
= 5V, V
POWER
= 3.3V, ÆV
OUT
= +1%
V
CONTROL
= 2.75V, V
POWER
= 2.05V, I
OUT
= 100mA
V
CONTROL
= 2.75V, V
POWER
= 2.05V, I
OUT
= 4A
V
CONTROL
= 2.75V, V
POWER
= 1.75V, I
OUT
= 4A
V
CONTROL
= 2.75V, V
POWER
= 2.05V, I
OUT
= 7A
V
CONTROL
= 2.75V, V
POWER
= 2.05V, I
OUT
= 10mA
V
CONTROL
= 2.75V, V
POWER
= 2.05V, ÆV
OUT
= -1.5%
V
CONTROL
= 2.75V, V
POWER
= 2.05V, V
OUT
= 0V
V
CONTROL
= V
POWER
= 3.25V,
V
RIPPLE
= 1V
P-P
@ 120Hz, I
OUT
= 4A, C
ADJ
= 0.1µF
30ms Pulse, T
A
= 25¡C
V
POWER
= 2.05V, I
OUT
= 100mA
V
POWER
= 2.05V, I
OUT
= 1A
V
POWER
= 2.05V, I
OUT
= 2.75A
V
POWER
= 2.05V, I
OUT
= 4A
V
POWER
= 2.05V, I
OUT
= 7A
V
CONTROL
= 2.75V, I
OUT
= 100mA
V
CONTROL
= 2.75V, I
OUT
= 1A
V
CONTROL
= 2.75V, I
OUT
= 2.75A
V
CONTROL
= 2.75V, I
OUT
= 4A
V
CONTROL
= 2.75V, I
OUT
= 7A
Freq = 10Hz to 10kHz, T
A
= 25¡C
1.234
(-1.5%)
1.253
.02
.04
5
6
30
33
60
60
1.272
(+1.5%)
.20
.20
10
10
60
70
180
120
V
%
%
mA
mA
mA
mA
mA
µA
A
A
dB
%/W
Adjust Pin Current
Current Limit
Short Circuit Current
Ripple Rejection
(Note 3)
Thermal Regulation
V
CONTROL
Dropout Voltage
(Minimum V
CONTROL
-V
OUT
)
(Note 4)
7.1
5.0
60
10.0
9.0
80
0.002
1.00
1.00
1.00
1.00
1.10
.10
.15
.20
.26
.35
0.003
0.5
1.15
1.15
1.15
1.15
1.25
.15
.20
.30
.40
.65
V
V
V
V
V
V
V
V
V
V
%V
OUT
%
V
POWER
Dropout Voltage
(Minimum V
POWER
-V
OUT
)
(Note 4)
RMS Output Noise
Temperature Stability
Thermal Shutdown (Note 5)
Thermal Shutdown Hysteresis
V
CONTROL
Supply Only
Output Current
150
V
CONTROL
= 13V, V
POWER
not connected,
V
ADJUST
= V
OUT
= V
SENSE
= 0V
180
210
25
50
¡C
¡C
mA
2
CS5257A-1
Electrical Characteristics:
0¡C ² T
A
² 70¡C, 0¡C ² T
J
² 150¡C, V
SENSE
= V
OUT
and V
Adj
= 0V unless otherwise specified.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
V
POWER
Supply Only
Output Current
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
V
POWER
= 6V, V
CONTROL
not connected,
V
ADJUST
= V
OUT
= V
SENSE
= 0V
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 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.
This parameter is guaranteed by design and is not 100% production tested.
Dropout is defined as either the minimum control voltage, (V
CONTROL)
or minimum power voltage (V
POWER
) to output voltage differential
required to maintain 1.5% 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
V
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.
This pin is connected to the low side of the internally trimmed 1.5% 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.
This pin is connected to the emitter of the power pass transistor and pro-
vides a regulated voltage capable of sourcing 7A of current.
This is the supply voltage for the regulator control circuitry. For the device
to regulate, this voltage should be between 1V and 1.25V (depending on the
output current) greater than the output voltage. The control pin current will
be about 1% of the output current.
This is the power input voltage. The pin is physically connected to the collec-
tor of the power pass transistor. For the device to regulate, this voltage
should be between 0.1V and 0.65V greater than the output voltage, depend-
ing on output current. The output load current of 7A is supplied through
this pin.
Block Diagram
2
Adjust
3
4
V
OUT
V
CONTROL
5
V
POWER
V
POWER
V
CONTROL
BIAS
and
TSD
V
REF
-
+
EA
IA
+
-
V
OUT
V
SENSE
Adjust
3
CS5257A-1
Typical Performance Characteristics
Reference Voltage vs Temperature
0.100
0.090
0.080
Output Voltage Deviation (%)
0.070
0.060
0.050
0.040
0.030
0.020
0.010
0.000
V
POWER
=2.05V
V
CONTROL
=2.75V
Load Regulation vs Output Current
0.100
0.075
0.050
Output Voltage Deviation (%)
0.025
-0.000
-0.025
-0.050
-0.075
-0.100
-0.125
-0.150
0 10 20 30 40 50 60 70 80 90 100 110120130
T
J
(°C)
I
0
=10mA
V
CONTROL
=2.75V,
V
POWER
=2.05V
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
Output Current (A)
Transient Response
100
Output Voltage Deviation (mV)
Short Circuit Current vs V
POWER
-V
OUT
15.0
14.0
13.0
12.0
11.0
10.0
9.0
8.0
7.0
6.0
5.0
4.0
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
5.5
50
0
Output Current (A)
V
CONTROL
=2.75V
-50
-100
C
OUT
=330mF
C
POWER
=110mF
C
CONTROL
=10mF
C
ADJUST
=0.1mF
V
CONTROL
=5V
V
POWER
=3.3V
V
OUT
=2.5V
Current (A)
7
0
0
0
1
2
3
Time (ms)
4
5
V
POWER
-V
OUT
(V)
Adjust Pin Current vs Temperature
83.0
Minimum Load Current vs V
CONTROL
-V
OUT
1200.000
81.0
Adjust Pin Current (mA)
1150.000
Minimum Load Current (mA)
79.0
77.0
75.0
73.0
71.0
69.0
67.0
65.0
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0 160.0
Temperature (C)
V
POWER
=3.3V
D
V
OUT
=+1%
1100.000
1050.000
1000.000
950.000
900.000
850.000
800.000
1.0 2.0
3.0
4.0
5.0
6.0
7.0 8.0
V
CONTROL
-V
OUT
(V)
9.0
10.0 11.0
4
CS5257A-1
Typical Performance Characteristics: continued
Adjust Pin Current vs V
CONTROL
-V
OUT
75.00
V
POWER
=2.05V
IL=10mA
74.00
Ripple Rejection vs Frequency
90.0
80.0
Ripple Rejection (dB)
Adjust Pin Current (mA)
70.0
60.0
50.0
40.00
30.0
20.0
V
IN
-V
OUT
=2V
I
OUT
=4A
V
RIPPLE
=1V
P-P
C
OUT
=22mF
C
ADJ
=0.1mF
10
1
10
2
10
3
10
4
10
5
10
6
73.00
72.00
71.00
70.00
1.0
2.0
3.0
4.0
5.0
6.0
7.0 8.0
V
CONTROL
-V
OUT
(V)
9.0
10.0 11.0
10.0
Frequency (Hz)
Adjust Pin Current vs V
POWER -
V
OUT
V
CONTROL
Dropout Voltage vs I
OUT
75.00
V
CONTROL
=2.75V
IL=10mA
V
CONTROL
Drop Out Voltage (V)
1.250
V
POWER
=2.05V
74.00
Adjust Pin Current (mA)
1.000
73.00
0.750
72.00
0.500
71.00
0.250
70.00
0.50
1.50
2.50
V
POWER
-V
OUT
(V)
3.50
4.50
0.00
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
Output Current (A)
V
POWER
Dropout Voltage vs I
OUT
1.000
0.900
V
POWER
Dropout Voltage (V)
0.800
0.700
0.600
0.500
0.400
0.300
0.200
0.100
0.000
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
Output Current (A)
V
CONTROL
=2.75V
Minimum Load Current vs V
POWER
-V
OUT
916.400
916.300
Minimum Load Current (mA)
916.200
916.100
916.000
915.900
915.800
915.700
915.600
915.500
915.400
0.50
1.50
2.50
V
POWER
-V
OUT
(V)
3.50
4.50
V
CONTROL
=5V
D
V
OUT
=+1%
5
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