Electronic Components Datasheet Search |
|
LT1573C Datasheet(PDF) 6 Page - Linear Technology |
|
LT1573C Datasheet(HTML) 6 Page - Linear Technology |
6 / 16 page 6 LT1573 – + – + – + VSHDNTH + I3 ILATCH + I2 VIN VIN SHDN GND COMP ERROR AMP VOUT IDISCHRG LATCH DRIVE NORMALLY OFF NORMALLY ON NORMALLY OFF NORMALLY OFF EXTERNAL CAPACITOR C1 C2 C4 C3 Q4 + ICHRG VDRSAT VIODTH VLATCHTH CEXT + + + THERMAL SHUTDOWN FB GND 1573 BD R1 R2 FOR FIXED VOLTAGE VERSION 1.265V 7 6 5 2 6 3 4 4 81 Q5 Q3 Q1 Q2 S3 S4 S2 S1 The basic block diagram of the LT1573 is shown above. The regulating loop consists of a 1.265V reference, an error amplifier, a Darlington driver and an external PNP pass transistor. The 1.265V reference feeds the noninvert- ing input of the error amplifier. The error amplifier drives the Darlington connected transistor pair Q1 and Q2. The collector of Q1 comes out to the DRIVE pin and is used to drive the base of an external PNP power transistor as shown in Figure 1. The error amplifier will adjust the drive current to the external PNP power transistor to maintain the feedback pin voltage at 1.265V. The LT1573 provides overcurrent protection by means of a timed latch function. Base current to the external PNP transistor is limited by placing a resistor between the base of the transistor and the DRIVE pin. When the DRIVE pin drops below VDRSAT (the DRIVE pin saturation voltage) the output of the comparator C2 switches high; S1, which is normally closed, opens and the external capacitor connected to the LATCH pin is allowed to charge. Discharge current IDISCHRG is equal to approximately 28 µAandchargingcurrentICHRG is equal to approximately 7 µA. If the fault condition goes away before CEXT charges to the latch threshold, C2 will switch back low, S1 will close and Q4 will discharge CEXT. If the fault condition persists long enough for CEXT to charge up to the latch threshold (VLATCHTH), comparator C4 will switch high and S4 will close and latch the output off. The device will stay latched because latching current ILATCH is greater than the pull-down current of Q4. Thermal shutdown circuitry will close S4 and latch the device off with no timing delay. Comparator C1 is used to override the latching function during start-up. If the difference between the output voltage and the input voltage is less than the input-output differential threshold (VIODTH), comparator C1 output goes high which closes S2. Current source I2 then drives base of Q4 which prevents CEXT from charging. Comparator C3 is used for system shutdown and latch reset. If SHDN pin voltage is higher than shut- down threshold VSDTH, the comparator C3 output goes high, shutting down the regulator and closing switch S3. Current I3 will drive Q4 to discharge CEXT, resetting the latch. BLOCK DIAGRA FU CTIO AL DESCRIPTIO |
Similar Part No. - LT1573C |
|
Similar Description - LT1573C |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | 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 |