TS39150 Datasheet, PDF (3/5 Pages) Taiwan Semiconductor Company, Ltd – 1.5A Ultra Low Dropout Fixed Positive Voltage Regulator

Application Information
Application Information
The TS39150 series are high performance with low
dropout voltage regulator suitable for moderate to high
current and voltage regulator application. Its
400mA(typ) dropout voltage at full load and over
temperature makes it especially valuable in battery
power systems and as high efficiency noise filters in
post regulator applications. Unlike normal NPN
transistor design, where the base to emitter voltage
drop and collector to emitter saturation voltage limit the
minimum dropout voltage, dropout performance of the
PNP output of these devices is limited only by low Vce
saturation voltage.
The TS39150 series is fully protected from damage due
to fault conditions. Linear current limiting is provided.
Output current during overload conditions is constant.
Thermal shutdown the device when the die temperature
exceeds the maximum safe operating temperature.
Transient protection allows device survival even when
the input voltage spikes above and below nominal. The
output structure of these regulators allows voltages in
excess of the desired output voltage to be applied
without reverse current flow.
Typical Application Circuit
Capacitor Requirement
The TS39150 series requires an output capacitor to
maintain stability and improve transient response is
necessary. The value of this capacitor is dependent
upon the output current, lower currents allow smaller
capacitors. TS39150 series regulators are stable with
the 10uF minimum capacitor value at full load. Where
the regulator is powered from a source with high AC
impedance, a 0.1uF capacitor connected between input
and ground is recommended. The capacitor should
have good characteristics to above 250KHz. The
capacitance values will be improved transient response,
ripple rejection and output noise.
Minimum Load Current
The TS39150 series is specified between finite loads.
If the output current is too small leakage currents
dominate and the output voltage rises. A 10mA
minimum load current swamps any expected leakage
current across the operating temperature range.
Thermal Characteristics
TS39150 series linear regulators are simple to use, the
most complicated design parameters to consider are
thermal characteristics, thermal design requires the
following application specification parameters:
z
Maximum ambient temperature, Ta
z
Output current, Iout
z
Output voltage, Vout
z
Input voltage, Vin
We calculate the power dissipation of the regulator
from these numbers and the device parameters from
this data sheet. A heatsink may be required depending
on the maximum power dissipation and maximum
ambient temperature of the application. Under all
possible operating conditions, the junction temperature
must be within the range specified under absolute
maximum ratings. To determine if the heatsink is
required, the power dissipated by the regulator, P_D
must be calculated.
The below formula shows the voltages and currents for
calculating the P_D in the regulator:
Iin = I_L / I_G
P_D = (Vin-Vout) * I_L + (Vin) * I_G
Ex. P_D = (3.3V-2.5V) * 1.5A + 3.3V * 11mA
= 1200mW + 36mW
= 1236mW
Remark: I_L is output load current,
I_G is ground current.
Vin is input voltage
Vout is output voltage
The next parameter which must be calculated is the
maximum allowable temperature rise, T_R(max). this is
calculated by the using to formula:
T_R(max) = T_J(max) – T_A(max)
Where: T_J(max) is the maximum allowable junction
temperature, which is 125^oC for commercial
grade parts.
T_A(max) is the maximum ambient
temperature which will be encountered in the
application.
TS39150
3-5
2005/3 rev. A