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LTC1326 Datasheet(PDF) 10 Page - Linear Technology |
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LTC1326 Datasheet(HTML) 10 Page - Linear Technology |
10 / 16 page 10 LTC1326/LTC1326-2.5 132625fc Figure 3 contains a simple circuit for 5V systems that can’t risk the RST output going high in the 3.1V to 4.15V range (possibly due to very slow rise time on the 5V supply). Diode D1 powers the LTC1326 while dropping ≈0.6V from the VCC5 pin to the VCC3 pin. This prevents the part’s internal override circuit from being activated. Without the override circuit active, the RST pin stays low until VCC5 reaches VRT5 ≅ 4.725V (See Figure 4). LTC1326-2.5 Override Functions The VCCA pin, if unused, can be tied to either VCC3 or VCC25. This is an obvious solution since the trip points for VCC3 and VCC25 will always be greater than the trip point for VCCA. Likewise, the VCC25, if unused, can be tied to VCC3. VCC3 must always be used. Tying VCC3 to VCC25 and operating off of a 2.5V supply will result in the continuous assertion of RST. Extending ESD Tolerance on the PBR Input Pin The PBR pin is susceptible to ESD since it may be brought out to a front panel in normal applications. The ESD tolerance of this pin can be increased by adding a resistor in series with the PBR pin. A 10k resistor can increase the ESD tolerance of the PBR pin to approximately 10kV. The PBR’s internal pull-up current of 7 µA typical means there is only 70mV (150mV max) dropped across the resistor. See Figure 5. APPLICATIO S I FOR ATIO PUSH-BUTTON RESET 1 2 3 4 8 7 6 5 VCC3 VCC25 VCCA GND PBR SRST RST RST LTC1326-2.5 3.3V SYSTEM RESET 2.5V R2 R1 1326 /2.5 F05 ADJUSTABLE SUPPLY OR DC/DC FEEDBACK DIVIDER 10k* *OPTIONAL RESISTOR EXTENDS ESD TOLERANCE OF PBR INPUT TO APPROXIMATELY 10kV Figure 5. Triple Supply Monitor (3.3V, 2.5V and Adjustable) with Extended ESD Tolerance 1 2 3 4 8 7 6 5 VCC3 VCC5 VCCA GND PBR SRST RST RST LTC1326 SYSTEM RESET 1326 /2.5 F03 5V 0.1 µF 4.7k D1* *MMBD914 OR EQUIVALENT VCC5 (V) 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 1326/2.5 F04 5 4 3 2 1 0 VCC5 = VCCA = 0V TO 5V 4.7k PULL-UP FROM RST TO VCC5 TA = 25°C Figure 3. LTC1326 Monitoring a Single 5V Supply. D1 Used to Avoid RST High Near 3.3V to 4V (See Figure 2). Figure 4. RST Output Voltage Characteristics of the Circuit in Figure 3 |
Similar Part No. - LTC1326_15 |
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Similar Description - LTC1326_15 |
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