Electronic Components Datasheet Search |
|
G923-270T1U Datasheet(PDF) 6 Page - Interpoint Corporation Company |
|
G923-270T1U Datasheet(HTML) 6 Page - Interpoint Corporation Company |
6 / 9 page Ver: 1.1 Jan 19, 2006 TEL: 886-3-5788833 http://www.gmt.com.tw 6 G923 Global Mixed-mode Technology Inc. Pin Description PIN NAME FUNCTION 1 SHDN Active-Low Shutdown Input. A logic low reduces the supply current to less than 1µA. Connect to IN for normal opera- tion. 2 GND Ground. This pin also functions as a heatsink. Solder to large pads or the circuit board ground plane to maxi- mize thermal dissipation. 3 IN Regulator Input. Supply voltage can range from +2.5V to +5.5V. Bypass with 1µF to GND 4 OUT Regulator Output. Fixed or adjustable from 1.25V to +5.5V. Sources up to 300mA. Bypass with a 1µF, <0.2 Ω typical ESR capacitor to GND. 5 SET Feedback Input for Setting the Output Voltage. Connect to GND to set the output voltage to the preset output voltage. Connect to an external resistor divider for adjustable-output operation. Detailed Description The block diagram of the G923 is shown in Figure 1. It consists of an error amplifier, 1.25V bandgap reference, PMOS output transistor, internal feedback voltage divider, mode comparator, shutdown logic, over current protec- tion circuit, and over temperature protection circuit. The mode comparator compares the SET pin voltage with an internal 350mV reference. If the SET pin volt- age is less than 350mV, the internal feedback voltage divider’s central tap is connected to the non-inverting input of the error amplifier. The error amplifier com- pares non-inverting input with the 1.25V bandgap ref- erence. If the feedback voltage is higher than 1.25V, the error amplifier’s output becomes higher so that the PMOS output transistor has a smaller gate-to-source voltage (VGS). This reduces the current carrying capa- bility of the PMOS output transistor, as a result the output voltage decreases until the feedback voltage is equal to 1.25V. Similarly, when the feedback voltage is less than 1.25V, the error amplifier causes the output PMOS to source more current to pull the feedback voltage up to 1.25V. Thus, through this feedback ac- tion, the error amplifier, output PMOS, and the voltage dividers effectively form a unity-gain amplifier with the feedback voltage force to be the same as the 1.25V bandgap reference. The output voltage, VOUT, is then given by the following equation: VOUT = 1.25 (1 + R1/R2). (1) Alternatively, the relationship between R1 and R2 is given by: R1 = R2 (VOUT /1.25 - 1). (2) For the reasons of reducing power dissipation and loop stability, R2 is chosen to be 100K Ω. For G923- 330, R1 is 164K, and the pre-set VOUT is 3.30V. When external voltage divider is used, as shown in Figure 2, the SET pin voltage will be larger than 350mV. The non-inverting input of the amplifier will be connected to the external voltage divider. However, the operation of the feedback loop is the same, so that the conditions of Equations 1 and 2 are still true. The output voltage is still given by Equation 1. Figure 1. Functional Diagram SHDN IN OUT SHUTDOWN LOGIC 1.25V Vref - ERROR AMP + OVER CURRENT PROTECT & DYNAMIC FEEDBACK - + + - GND MODE COMPARATOR 350mV SET R1 R2 OVER TEMP. PROTECT P SHDN IN OUT SHUTDOWN LOGIC 1.25V Vref - ERROR AMP + OVER CURRENT PROTECT & DYNAMIC FEEDBACK - + + - GND MODE COMPARATOR 350mV SET R1 R2 OVER TEMP. PROTECT P |
Similar Part No. - G923-270T1U |
|
Similar Description - G923-270T1U |
|
|
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 |