ltc4350 Linear Technology Corporation, ltc4350 Datasheet
ltc4350
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ltc4350 Summary of contents
Page 1
... The output voltage of each supply is adjusted using the SENSE the share bus. The LTC4350 also isolates supply failures by turning off the series pass transistors and identifying the failed supply. The failed supply can then be removed and replaced with a new unit without turning off the system power ...
Page 2
... unless otherwise noted CONDITIONS 0°C to 85°C (LTC4350I) or 0°C to 70°C (LTC4350C) – 40°C to 85°C (LTC4350I 3.3V to 12V, COMP1 = 1.240V CC COMP1 = 2V COMP1 = 0.64V High Going Threshold ...
Page 3
... TEMPERATURE (°C) OV Threshold 1.222 T = 25°C A 1.220 1.218 1.216 1.214 1.212 1.210 1.208 1.206 1.204 1.202 100 (V) CC LTC4350 MIN TYP MAX ● 0.94 1 ● 0.94 1 ● 0.001 ● 0.001 ● ● ● 10.8 12 ● – 8 –10 ● ...
Page 4
... LTC4350 W U TYPICAL PERFOR A CE CHARACTERISTICS 1.230 T = 25°C A 1.225 1.220 1.215 1.210 (V) CC 4350 G07 Gain Pin Voltage vs Temperature 2 25k GAIN + – (V – 100mV 2.6 2.5 2.4 2.3 2.2 – –25 TEMPERATURE (°C) 4350 G10 ...
Page 5
... SET . This current then a 51Ω decoupling resistor is needed to hold up the SET supply during a short to ground on the supply output. V must be greater than or equal to the supply that is connected to the R LTC4350 + – and R pins, the power block and SENSE + – ...
Page 6
... LTC4350 W BLOCK DIAGRA COMP1 6 REF FB 9 REVERSE CURRENT + R 30mV + – – REF – REF GATE V CC CHARGE PUMP + E/A1 – + E/A2 – OVER/UNDER CURRENT – – – + LOGIC GND – – SENSE Ω GAIN 20k COMP2 ...
Page 7
... The objective of the E/A2 block is forcing the OUT GAIN pin voltage to equal the SB pin voltage. When the GAIN pin voltages of all the LTC4350s in the system equal the SB pin voltage, the load current is shared. VOLTAGE MONITOR Unique to the LTC4350 is tight output voltage regulation. ...
Page 8
... This is normally done using the trim pin of the module. The power supply output is then increased by artificially reducing the positive sense voltage by a small amount. The LTC4350 would then adjust the output voltage to 5V, an increase of 2%. The maximum range of adjustment can be set from compensate for voltage drops in the wiring, but no more than 300mV ...
Page 9
... E/A1 and E/A2. In the Design Example section, the calculations for choosing all of the components will be discussed. Output Adjust Soft-Start In the LTC4350, there is soft-start circuitry that holds the COMP2 pin at ground until both the GATE pin is 4V above the V pin and a timer cycle is completed following the CC UV pin becoming active ...
Page 10
... If the power supply output fails to share properly, the E/A2 output will hit the plus or minus supply. The LTC4350 uses the over/ under current block to monitor the E/A2 output. This block signals the logic that a soft fault has occurred if the E/A2 output goes out of the normal 0 ...
Page 11
... Since the starting voltage is 4.9V ±0.1V, then the lowest starting voltage can be 4.8V. This voltage is 0.2V below the target. The total adjustment range that the LTC4350 will need for this example is 0.1V + 0.2V = 0.3V. Note that the lowest starting voltage should not be lower than 300mV below the target voltage. ...
Page 12
... LTC4350 U U APPLICATIO S I FOR ATIO The resistors R and R set the adjustment range. The OUT SET voltage translated to a voltage on R SET ratio Therefore, the adjustment on the OUT SET output voltage will track the voltage at the R is also the voltage on the COMP2 pin minus a diode voltage ...
Page 13
... In some cases, the output voltage is below the undervoltage 10µF lockout of the LTC4350. In this case, an external supply of 12µF 3.3V or greater needs to provide for the chip. Figure 8 shows a 1.5V output redundant power supply that uses 24V to 1.5V switching power supplies. The V ...
Page 14
... GAIN GAIN SB LTC4350 GND TIMER COMP1 C COMP2 SENSE 3. OUT GATE OUT – SET R SET FB R STATUS GAIN GAIN SB LTC4350 GND TIMER COMP1 C COMP2 4350 F07 4350fa ...
Page 15
... TYP .008 – .012 (0.203 – 0.305) TYP INCHES LTC4350 .189 – .196* (4.801 – 4.978) .009 (0.229 REF .150 – .157** (3.810 – 3.988) ...
Page 16
... COMP2 SENSE GATE OUT OUT – SET R SET FB R STATUS GAIN GAIN SB LTC4350 GND TIMER COMP1 C COMP2 LT/TP 1004 1K REV A • PRINTED IN THE USA © LINEAR TECHNOLOGY CORPORATION 2001 1.5V 1.5V 4350fa ...