TS1581
5A Dual Input Low Dropout Positive Voltage Regulator
Pin Assignment:
1. Sense
2. Adj / Gnd
3. Output
4. V control
5. V power
Low Dropout Voltage 0.7V max.
Fix or Adjustable Output
General Description
The TS1581 family is a positive adjustable and fixed voltage regulator developed to provide 5A with Higher efficiency than
currently available devices. All internal circuit is designed to operate down to 700mV input to output differential and the
dropout voltage is fully specified as a function of load current. Dropout voltage of the device is 100mV at light loads and
rising to 700mV at maximum output current. A Second low current input is required to achieve this dropout. The TS1581
series are designed to prevent device failure under the worst operation condition with both Thermal Shutdown and
Current Fold-back.
Features
Very low dropout voltage: 700mV @5A
Output current up to 5A
Low current Consumption
High Accuracy Output Voltage: +/- 1%
Fast transient response
Remote sense
Internal current limit
Thermal shutdown protection
Ordering Information
Part No.
TS1581CZ5xx
TS1581CZ5
TS1581CM5xx
0 ~ +85
o
C
TO-263-5L
Operating Temp.
(Ambient)
Package
TO-220-5L
Applications
High efficiency linear voltage regulators
Post regulators for switching supplies.
Advance graphic card
Adjustable power supply
TS1581CM5
Note: Where
xx
denotes voltage option, available are
3.3V and 2.5V. Leave blank for adjustable version.
Contact factory for additional voltage options.
Typical Application Circuit
Block Diagram
TS1581 series
1-1
2003/12 rev. B
Absolute Maximum Rating
Input Supply Voltage
V power
V control
Power Dissipation
Operating Junction Temperature Range
Storage Temperature Range
Lead Soldering Temperature (260
o
C)
TO-220-5L / TO-263-5L Package
10
S
Vpower
Vcontrol
P
D
T
J
T
STG
7
13
Internally Limited
0 ~ +125
-65 ~ +150
W
o
o
V
C
C
Electrical Characteristics
Tj=+25°C, Ccontrol=Cpower=Cout=10uF unless Specified
Parameter
Reference Voltage
(Adj. Voltage Versions)
Conditions
V
CONTROL
= 4.5V, V
POWER
= 2.05V, I
O
= 10mA
V
CONTROL
= 4.5V, V
POWER
= 2.05V,
I
O
= 10mA to 5A
V
CONTROL
= 5V, V
POWER
=V
OUT
+0.8V,I
O
=10mA
V
CONTROL
= 5V, V
POWER
= V
OUT
+0.8V,
I
O
= 10mA to 5A
V
CONTROL
= (Vout+1.5V) to 12V,
V
POWER
= (V
OUT
+0.8V) to 5.5V, I
O
= 10mA
V
CONTROL
= (Vout+2.5V),
V
POWER
= (V
OUT
+0.8V), I
O
= 10mA to 5A
V
CONTROL
=5V, V
POWER
= 3.3V, V
ADJ
=0V
V
CONTROL
= (V
OUT
+2.5V),
V
POWER
= (V
OUT
+0.8V), I
O
= 10mA to 5A
V
CONTROL
= 2.75V, V
POWER
= 2.05, V
ADJ
= 0V,
I
O
= 10mA
V
POWER
- V
OUT
= 3V
V
CONTROL
= V
POWER
= 5V, V
RIPPLE
= 1V,
I
O
= 2.5A, f = 120kHz
30mS pulse
V
CONTROL
= (Vout+2.5V), I
O
= 5A
Min
1.238
1.230
Typ
1.250
Max
1.262
1.270
Unit
V
Output Voltage
(Fixed Voltage Versions)
-1.0
-1.6
V
OUT
+1.0
+1.6
0.2
%
Line Regulation
0.04
%
Load Regulation
Mini. Load Current (Note 2)
Control Pin Current (Note 3)
0.08
0.4
%
mA
mA
5
80
10
135
Adjust Pin Current
Current Limit
Ripple Rejection
Thermal Regulation
Dropout Voltage (Note 4)
50
5.5
60
6.8
80
0.003
0.55
120
uA
A
dB
%/W
0.70
V
Note1: V
OUT
= V
SENSE,
V
ADJ
= 0V unless otherwise specified.
Note2: For the adjustable device 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.
Note3: The control pin current is the drive current required for the output transistor, this current will track output current
with a ratio of about 1:100
Note4: If the same voltage is input to both V
POWER
and V
CONTROL
, then the dropout voltage will become 1.3V maximum,
and minimum input/output voltage required to maintain 1% regulation.
TS1581 series
2-2
2003/12 rev. B
Thermal Performance
Condition
Thermal Resistance
Junction to Ambient
Package type
TO-220-5L
TO-263-5L
Typ
50
60
Unit
o
C/W
Pin Description
Pin No.
Pin Name
Pin Description
This pin is the positive side of the reference voltage for this device. With this pin it is
possible to Kelvin Sense the output voltage at the load.
2
Adjust / Ground
This pin is the negative side of the reference voltage for this device. Transient
response can be improved by adding a small bypass capacitor from the adjust pin to
ground.
3
4
Output
Control
This pin is power output of the device.
This pin is the supply pin for the control circuitry for the device. The current flow into
this pin will be about 1% of the output current. For the device to regulate, the voltage
at this pin must be 1.3V greater than the output voltage.
5
Power
This pin is the collector of the power transistor. The output load current is supplied
through this pin. The voltage at this pin must be 0.7V greater than the output voltage
for the device to regulate.
1
Sense
TS1581 series
3-3
2003/12 rev. B
Application Information
Application
The TS1581 is a low dropout regulator designed to
make used of multiple power supplies, present in most
systems, to reduce the dropout voltage. One of the
advantages of the two supply approach is maximizing
the efficiency. The second supply is at least 1V greater
than output voltage and is providing the power for the
control circuitry and supplies the drive current to the
NPN output transistor. This allows the NPN output
transistor to be driven into saturation. For the control
voltage the current requirement is small equal to about
1% of the output current or approximately 50mA for a
5A load. This drive current becomes part of the output
current. The maximum voltage on the Control Pin is
15V. The maximum voltage at the Power in is 7V.By
tying the control and power inputs together the TS1581
can also be operated as a single supply device. In
single supply operation the dropout will be determined
by the minimum control voltage.
Both the fixed and adjustable versions have remote
sense pins, permitting very accurate regulation of
output voltage. As a result, over and output current
range of 100mA to 5A, the typical load regulation is
less than 1mV. For the fixed voltages the adjust pin is
brought out allowing the user to improve transient
response by bypassing the internal resistor divider.
Optimum transient response is provided using a
capacitor in the range of 0.1uF to 1uF for bypassing the
adjust pin.
The new generation of microprocessors cycle load
current from several hundred million amperes to
several amperes in tens of nanoseconds. Output
voltage tolerances are tighter and include transient
response as part of the specification. Designed to meet
the fast current load step requirements of these
microprocessors, the TS1581 also saves total cost by
needing less output capacitance to maintain regulation.
Typical applications for the TS1581 include 3.3V to
2.5V conversion with a 5V control supply, 5V to 4.2V
conversion with a 12V control supply or 5V to 3.6V
conversion with a 12V control supply. It is easy to
obtain dropout voltages less than 0.5V at 1.5A along
with excellent static and dynamic specifications. It is
fully protected against over current and over
temperature conditions.
Grounding and Output Sensing
The TS1581 allows true Kelvin sensing for both the
high & low side of the load. A result the voltage
regulation at the load can be easily optimized. Voltage
drops due to parasitic resistances between the
regulator and the load can be placed inside the
regulation loop. The advantages of remote sensing are
illustrated in Figure 1 through 3.
Figure 1 show the device connected as a conventional
3 terminal regulator with the Sense lead connected
directly to the output of the device. Rp is the parasitic
resistance of the connections between the device and
the load. Trace A of Figure 3 illustrates the effect of Rp
Figure 1. Conventional Load Sensing
Figure 2 show the device connected to take advantage
of the remote sense feature. The Sense Pin and the
top of the resistor divider are connected to the top of
the load; the bottom of the resistor divider is connected
to the bottom of the load.
Figure 2. Remote Load Sensing
TS1581 series
4-4
2003/12 rev. B
Application Information (continued)
The effect on output regulation can be seen in trace B
of Figure 3. It is important to note that the voltage drops
due to Rp are not eliminated; they will add to the
dropout voltage of the regulator regardless. The
TS1581 can control the voltage at the load as long as
the input-output voltage is greater than the total of the
dropout voltage of the device plus the voltage drop
across Rp
Figure 3. Remote Sensing Improves Load Regulation
Because they contain parasitic resistance and
inductance, capacitors are not ideal elements. These
parasitic elements dominate the change in output
voltage as the beginning of a transient load step
change. The ESR of the output capacitors produces
and instantaneous step in output voltage
∆V
=
∆I
(ESR). The ESL of the output capacitors
produces a drop proportional to the rate of change of
the output current V = L (∆I /
∆t).
the output
capacitance produces a change in output voltage
proportional to the time until the regulator can respond
∆V
=
∆t
(∆I / C).
Figure 4. illustrates there transient effects.
Stability
The circuit design used in the TS1581 Series requires
the use of an output capacitor as part of the device
frequency compensation. The addition of 150uF
aluminum electrolytic or a 22uF solid tantalum on the
output will ensure stability for all operating conditions.
In order to meet the transient performance of the
processor larger value capacitors are needed. To limit
the high frequency noise generated by the processor
high quality bypass capacitors must be used. In order
to limit parasitic inductance (ESL) and resistance
(ESR) in capacitors to acceptable limits, multiple small
ceramic capacitors in addition to high quality solid
tantalum capacitors are required.
When the adjustment terminal is bypass to improve the
ripple rejection, the requirement for an output capacitor
increases. The Adjust pin is brought out on the fixed
voltage device specifically to allow this capability. To
further improve stability and transient response of
these devices larger values of output capacitor can be
used. The modern processors generate large high
frequency current transients. The load current step
contains higher order frequency components than the
output coupling network must handle until the regulator
throttles to the load current level.
Output voltage
The TS1581 (adjustable version) develops a 1.25V
reference voltage between the Sense Pin and the
Adjust Pin (Figure 5). Placing a resistor between these
two terminals causes a constant current to flow though
R1 and down though R2 to set the output voltage. In
general R1 is chosen so that this current is the
specified minimum load current of 10mA. The current
out of the Adjust pin is small, typically 50uA and it adds
to the current from R1.For best regulation the top of the
resistor divider should be connected directly to the
Sense pin.
Figure 5. Setting Output Voltage
TS1581 series
5-5
2003/12 rev. B
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