ISSUED DATE :2005/06/21
REVISED DATE :2005/10/04B
The GSC2129 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
140 : , or the current exceeds 2.2A. During thermal shutdown, the output voltage remains low. Normal
operation is restored when the junction temperature drops below 120 : .
Detailed Description
The GSC2129 is stable with an output capacitance to ground of 4.7 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. Unfortunately, large value ceramic capacitors are
comparatively expensive. One option is to parallel a 0.1 F ceramic capacitor with a 10 F Aluminum Electrolytic.
The benefit is low ESR, high capacitance, and low overall cost.
A second capacitor is recommended between the input and ground to stabilize Vin. The input capacitor
should be at least 0.1 F to have a beneficial effect.
A third capacitor can be connected between the BY-PASS pin and GND. This capacitor can be a low cost
Polyester Film variety between the value of 0.001~0.01 F. 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.
External Capacitors
Enable
When 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.
Important Notice:
All rights are reserved. Reproduction in whole or in part is prohibited without the prior written approval of GTM.
GTM reserves the right to make changes to its products without notice.
GTM semiconductor products are not warranted to be suitable for use in life-support Applications, or systems.
GTM assumes no liability for any consequence of customer product design, infringement of patents, or application assistance.
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