TS1581
5A Dual Input LDO
TO-220-5L
TO-263-5L
2
(D PAK)
Pin Definition:
1. Sense
2. Adj / Gnd
3. Output
4. V Control
5. V Power
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
●
●
●
●
●
●
●
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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.
Package
Packing
TS1581CZ5 C0
TO-220-5L
50pcs / Tube
TS1581CZ5xx C0
TO-220-5L
50pcs / Tube
TS1581CM5 RN
TO-263-5L
800pcs / 13” Reel
TS1581CM5xx RN
TO-263-5L
800pcs / 13” Reel
Note: Where
xx
denotes voltage option, available are
3.3V, 2.5V & 1.8V. Leave blank for adjustable
version.
Contact factory for additional voltage options.
Applications
●
●
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High efficiency linear regulator
Post regulators for switching supplies
Advance graphic card
Adjustable power supply
Typical Application Circuit
Block Diagram
1/9
Version: A07
TS1581
5A Dual Input LDO
Absolute Maximum Rating
Parameter
Input Supply Voltage
V Power
V Control
Power Dissipation
Operating Junction Temperature Range
Storage Temperature Range
Lead Soldering Temperature (260 C)
o
Symbol
Vpower
Vcontrol
P
D
T
J
T
STG
Value
7
13
Internally Limited
0 ~ +125
-65 ~ +150
10
Units
V
W
o
o
C
C
S
Electrical Characteristics
Ta=+25°C, Ccontrol=Cpower=Cout=10uF unless Specified
Parameter
Reference Voltage
(Adj. Voltage Versions)
Output Voltage
(Fixed Voltage Versions)
Line Regulation
Load Regulation
Mini. Load Current (Note 2)
Control Pin Current
(Note 3)
Adjust Pin Current
Current Limit
Ripple Rejection
Thermal Regulation
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
= (V
OUT
+1.5V) to 12V,
V
POWER
= (V
OUT
+0.8V) to 5.5V, I
O
= 10mA
V
CONTROL
= (V
OUT
+2.5V),
V
POWER
= (V
OUT
+0.8V), I
O
= 10mA to 5A
V
CONTROL
=5V, V
POWER
= 3.3V, VADJ=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
Min
1.238
1.230
-1.0
-1.6
--
--
--
--
--
5.5
60
--
Typ
1.250
Max
1.262
1.270
+1.0
Unit
V
VOUT
+1.6
0.2
0.4
10
135
120
--
--
--
%
0.04
0.08
5
80
50
6.8
80
0.003
%
%
mA
mA
uA
A
dB
%/W
Dropout Voltage (Note 4)
V
CONTROL
= (V
OUT
+2.5V), I
O
= 5A
--
0.55
0.70
V
Note1: VOUT = VSENSE, VADJ = 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.
2/9
Version: A07
TS1581
5A Dual Input LDO
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.
1
2
3
4
Pin Name
Sense
Adjust /
Ground
Output
Control
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.
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.
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.
This pin is the collector of the power transistor. The output load current is supplied
5
Power
through this pin. The voltage at this pin must be 0.7V greater than the output voltage for
the device to regulate.
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.
3/9
Version: A07
TS1581
5A Dual Input LDO
Application Information (Continue)
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 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 1. Conventional Load Sensing
Figure 2. Remote Load Sensing
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
Figure 4. Illustrates there transient effects
4/9
Version: A07
TS1581
5A Dual Input LDO
Application Information (Continue)
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.
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
ΔV
=
ΔI
(ESR). The ESL of the output capacitors produces a drop proportional to the rate of change of the output
current V = L (ΔI /
Δt).
the output capacitance produces a change in output voltage proportional to the time until the
regulator can respond
ΔV
=
Δt
(ΔI / C).
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
Figure 6. Optional Clamp Diodes Protect
Against Input Crowbar Circuits
5/9
Version: A07
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