ISSUED DATE :2005/12/12
REVISED DATE :
Ordering Information ( contd. )
Part Number
GQ2181-15
GQ2181-20
GQ2181-27
GQ2181-2H
GQ2181-32
XXXX
XXXX
XXXX
XXXX
XXXX
Marking
1L152
1L202
1L272
1L2H2
Output Voltage
1.5V
2.0V
2.7V
2.85V
3.2V
Part Number
GQ2181-18
GQ2181-25
GQ2181-28
GQ2181-30
GQ2181-33
XXXX
XXXX
XXXX
XXXX
XXXX
Marking
1L182
Output Voltage
1.8V
2.5V
2.8V
3.0V
3.3V
1L252
1L282
1L302
1L332
1L322
The GQ2181 series of COMS regulators contain a PMOS pass transistor, voltage reference, error amplifier,
over-current protection, and thermal shutdown.
The P-channel pass transistor receives data from the error amplifier, over-current shutdown, and thermal
protection circuits. During normal operation, the error amplifier compares the output voltage to a precision
reference. Over-current and Thermal shutdown circuits become active when the junction temperature exceeds
150 : , or the current exceeds 150mA. During thermal shutdown, the output voltage remains low. Normal
operation is restored when the junction temperature drops below 120 : .
The GQ2181 switches from voltage mode to current mode when the load exceeds the rated output current.
This prevents over-stress. The GQ2181 also incorporates current fold-back to reduce power dissipation when
the output is short circuited. This feature becomes active when the output drops below 0.8 volts, and reduces
the current flow by 65%. Full current is restored when the voltage exceeds 0.8 volts.
The GQ2181 is stable with an output capacitance to ground of 0.22 F or greater. Ceramic capacitors have the
lowest ESR, and will offer the best AC performance. Conversely, Aluminum Electrolytic capacitors exhibit the
highest ESR, resulting in the poorest AC response.
A second capacitor is recommended between the input and ground to stabilize Vin. The input capacitor should
be at least 1 F to have a beneficial effect.
A large capacitor improves the AC ripple rejection, but also makes the output come up slowly. This “Soft”
turn-on is desirable in some applications to limit turn-on surges.
All capacitors should be placed in close proximity to the pins. A “Quiet” ground termination is desirable. This
can be achieved with a “Star” connection.
When actively, pulled low, the PMOS pass transistor shuts off, and all internal circuits are powered down. In
this state, the quiescent current is less than 1 A. This pin behaves much like an electronic switch.
Detailed Description
External Capacitors
Shutdown
Characteristics Curve
3/5
GTM [ GTM CORPORATION ]
