TS2937 Taiwan Semiconductor Company, TS2937 Datasheet - Page 3

• Manufacturer Part Number: TS2937
• Description: 500mA Ultra Low Dropout Fixed Positive Voltage Regulator
• Manufacturer: Taiwan Semiconductor Company

TS2937
Application Information
The TS2937 series is a high performance with low dropout
voltage regulator suitable for moderate to high current and
voltage regulator application. Its 600mV(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 TS2937 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
The TS2937 series requires an output capacitor to
maintain stability and improve transient response. Proper
capacitor selection is important to ensure proper
operation. The output capacitor selection is dependent
upon the ESR of the output capacitor the maintain
stability. When the output capacitor is 10uF or greater, the
output capacitor should have an ESR less than 2 ohm.
This will improve transient response as well as promoted
stability. Ultra low ESR capacitors (<100mohm), such as
ceramic chip capacitors may promote instability. These
very low ESR levels may cause an oscillation and/or
under damped transient response. A low ESR solid
tantalum capacitor works extremely well and provides
good transient response and stability over
Output Capacitor
3-3
temperature. Aluminum electrolytic can also be
used, as long as the ESR of the capacitor is <2ohm.
The value of the output capacitor can be increased
without limit. Higher capacitance values help to
improved transient response and ripple rejection and
reduce output noise.
Minimum Load Current
The TS2937 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 is necessary for proper
regulation.
Input Capacitor
An
recommended when the device is more that 4
inches away from the bulk AC supply capacitance or
when the supply is a battery. Small and surface
mount ceramic chip capacitors can be used for
bypassing. Larger values will help to improve ripple
rejection by bypassing the input to the regulator,
further improving the integrity of the output voltage.
Thermal Characteristics
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
must be calculated.
The below formula shows the voltages and currents
for calculating the P
Iin = I
P
Ex. P
Remark: I
The next parameter which must be calculated is the
maximum allowable temperature rise.
D
= (Vin-Vout) * I
D
input
L
/ I
= (3.3V-2.5V) * 0.5A + 3.3V * 11mA
= 400mW + 36mW
= 436mW
G
I
Vin is input voltage
Vout is output voltage
G
L
is output load current,
is ground current.
capacitor
L
+ (Vin) * I
D
in the regulator:
2003/12 rev. B
of
G
1uF
or
greater
is
D