TS2940 Taiwan Semiconductor Company, TS2940 Datasheet - Page 3

• Manufacturer Part Number: TS2940
• Description: 1A Ultra Low Dropout Fixed Positive Voltage Regulator
• Manufacturer: Taiwan Semiconductor Company

TS2940
Application Information
The TS2940 series is a high performance with low dropout
voltage regulator suitable for moderate to high current and
voltage regulator application. Its 600mA(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 TS2940 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
Output Capacitor
The TS2940 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.
3-6
A low ESR solid tantalum capacitor works extremely
well and provides good transient response and
stability over 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 TS2940 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 input capacitor of 1uF or greater is 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
D
= (Vin-Vout) * I
D
L
I
Vin is input voltage
Vout is output voltage
= 800mW + 36mW
= 836mW
/ I
= (3.3V-2.5V) * 1A + 3.3V * 11mA
G
G
is ground current.
L
is output load current,
L
+ (Vin) * I
D
in the regulator:
2003/12 rev. B
G
D