 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
G914FF Datasheet(PDF) 9 Page - Global Mixed-mode Technology Inc |
|
||||||||||||||||||||||||||||||
G914FF Datasheet(HTML) 9 Page - Global Mixed-mode Technology Inc |
|
|
9 / 11 page  Ver: 1.8 Jul 24, 2007 TEL: 886-3-5788833 http://www.gmt.com.tw 9 G914X Global Mixed-mode Technology Inc. Over Current Protection The G914X use a current mirror to monitor the output current. A small portion of the PMOS output transistor’s current is mirrored onto a resistor such that the voltage across this resistor is proportional to the output current. This voltage is compared against the 1.25V reference. Once the output current exceeds the limit, the PMOS output transistor is turned off. Once the output transistor is turned off, the current monitoring voltage decreases to zero, and the output PMOS is turned on again. If the over current condition persist, the over current protec- tion circuit will be triggered again. Thus, when the output is shorted to ground, the output current will be alternat- ing between 0 and the over current limit. The typical over current limit of the G914X is set to 500mA. Note that the input bypass capacitor of 1µF must be used in this case to filter out the input voltage spike caused by the surge current due to the inductive effect of the package pin and the printed circuit board’s routing wire. Otherwise, the actual voltage at the IN pin may exceed the absolute maximum rating. Over Temperature Protection To prevent abnormal temperature from occurring, the G914X has a built-in temperature monitoring circuit. When it detects the temperature is above 150°C, the output transistor is turned off. When the IC is cooled down to below 135°C, the output is turned on again. In this way, the G914X will be protected against abnor- mal junction temperature during operation. Shutdown Mode When the SHDN pin is connected a logic low voltage, the G914X enters shutdown mode. All the analog cir- cuits are turned off completely, which reduces the cur- rent consumption to only the leakage current. The out- put is disconnected from the input. When the output has no load at all, the output voltage will be discharged to ground through the internal resistor voltage divider. Operating Region and Power Dissipation Since the G914X is a linear regulator, its power dissi- pation is always given by P = IOUT (VIN – VOUT). The maximum power dissipation is given by: PDMAX = (TJ – TA)/θJA = (150-25) / 240 = 520mW Where (TJ – TA) is the temperature difference the G914X die and the ambient air, θJA, is the thermal resistance of the chosen package to the ambient air. For surface mount device, heat sinking is accom- plished by using the heat spreading capabilities of the PC board and its copper traces. In the case of a SOT-23-5 package, the thermal resistance is typically 240°C/Watt. (See Recommended Minimum Footprint). Refer to Figure 2 is the G914X valid operating region (Safe Operating Area) & refer to Figure 3 is maximum power dissipation of SOT-23-5. The die attachment area of the G914X’s lead frame is connected to pin 2, which is the GND pin. Therefore, the GND pin of G914X can carry away the heat of the G914X die very effectively. To improve the power dis- sipation, connect the GND pin to ground using a large ground plane near the GND pin. Applications Information Capacitor Selection and Regulator Stability Normally, use a 1µF capacitor on the input and a 4.7µF capacitor on the output of the G914X. Larger input ca- pacitor values and lower ESR provide better sup- ply-noise rejection and transient response. A higher- value input capacitor (10µF) may be necessary if large, fast transients are anticipated and the device is located several inches from the power source. For stable opera- tion over the full temperature range, with load currents up to 120mA, a minimum of 4.7µF is recommended. Power-Supply Rejection and Operation from Sources Other than Batteries The G914X is designed to deliver low dropout voltages and low quiescent currents in battery powered sys- tems. Power-supply rejection is 70dB at low frequen- cies as the frequency increases above 20kHz; the output capacitor is the major contributor to the rejec- tion of power-supply noise. When operating from sources other than batteries, improve supply-noise rejection and transient response by increasing the values of the input and output ca- pacitors, and using passive filtering techniques. Load Transient Considerations The G914X load-transient response graphs show two components of the output response: a DC shift of the output voltage due to the different load currents, and the transient response. Typical overshoot for step changes in the load current from 0mA to 100mA is 12mV. Increasing the output capacitor’s value and decreasing its ESR attenuates transient spikes. Input-Output (Dropout) Voltage A regulator’s minimum input-output voltage differential (or dropout voltage) determines the lowest usable supply voltage. In battery-powered systems, this will determine the useful end-of-life battery voltage. Be- cause the G914X use a P-channel MOSFET pass transistor, their dropout voltage is a function of RDS(ON) multiplied by the load current cause the G914X use a P-channel MOSFET pass transistor, their dropout voltage is a function of RDS(ON) multiplied by the load current. |
Similar Part No. - G914FF |
|
Similar Description - G914FF |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.COM |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
