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TPS3513N Datasheet(PDF) 6 Page - Texas Instruments |
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TPS3513N Datasheet(HTML) 6 Page - Texas Instruments |
6 / 20 page TPS3513 SLVS313B – FEBRUARY 2001 – REVISED SEPTEMBER 2010 www.ti.com The TPS3513 family of power-supply supervisors provides a power-good output (PGO) for the 3.3-V and 5-V supply voltage rails and a separate power-good input (PGI). An internal timer is used to generate a 300-ms power-good delay. If the voltage signals at PGI, VS33, and VS5 rise above the undervoltage threshold, the open-drain, power-good output (PGO) will go high after a delay of 300 ms. When the PGI voltage or any of the 3.3-V, 5-V rail drops below the undervoltage threshold, PGO will be disabled immediately. Power-Supply Remote On/Off (PSON) and Fault Protect Output (FPO) Since the latest personal computer generation focuses on easy turnon and power saving functions, the PC power supply will require two characteristics. One is a dc power supply remote on/off function; the other is standby voltage to achieve very low power consumption of the PC system. Thus, the main power needs to be shut down. The power supply remote on/off (PSON) is an active-low signal that turns on all of the main power rails including the 3.3-V, 5-V, -5-V, and -12-V power rails. When this signal is held high by the PC motherboard or left open circuited, the signal of the fault protect output (FPO) also goes high. Thus, the main power rails should not deliver current and should be held at 0 V. When the FPO signal is held high due to an occurring fault condition, the fault status will be latched and the outputs of the main power rails should not deliver current and should be held at 0 V. Toggling the power-supply remote on/off (PSON) from low-to-high will reset the fault-protection latch. During this fault condition only the standby power is not affected. When PSON goes from high to low or low-to-high, the 38-ms debounce block will be active to avoid that a glitch on the input will disable/enable the FPO output. During this period, the undervoltage function is disabled to prevent turnon failure. Power should be delivered to the rails only if the PSON signal is held at ground potential, thus, FPO is active low. The FPO pin can be connected to 5 VDC (or up to 15 VDC) through a pullup resistor. Under-Voltage Protection The TPS3513 provides undervoltage protection (UVP) for the 12-V rail and undervoltage detect for the 3.3-V and 5-V rails. When an undervoltage condition appears at the VS12 input pin for more than 150 µs, the FPO output goes high and PGO goes low. Also, this fault condition will be latched until PSON is toggled from low-to-high or VDD is removed. In flyback or forward type off-line switching power supplies, usually designed for small power, the overload protection design is very simple. Most of these type of power supplies are only sensing the input current for an overload condition. The trigger-point needs to be set much higher than the maximum load in order to prevent false turnon. However, this will cause one critical issue. In case that the connected load is larger than the maximum allowable load but smaller than the trigger-point, the system will always become over-heated and cause failure and damage. Overcurrent Protection In bridge or forward type, off-line switching power supplies, usually designed for medium to large power, the overload protection design needs to be very precise. Most of these types of power supplies are sensing the output current for an overload condition. The trigger-point needs to be set higher than the maximum load in order to prevent false turnon. The TPS3513 provides overcurrent protection (OCP) for the 3.3-V, 5-V, and 12-V rails. When an over current condition appears at the OCP comparator input pins for more than 73 µs, the FPO output goes high and PGO goes low. Also, this fault condition will be latched until PSON is toggled from low-to-high or VDD is removed. The resistor connected between the RI pin and the GND pin will introduce an accurate I(ref) for the OCP function. Of course, a more accurate resistor tolerance will be better. The formula for choosing the RI resistor is V(RI)/I(ref). The I(ref) range is from 12.5 µA to 62.5 mA. Three OCP comparators and the I(ref) section are supplied by VS12. Current drawn from the VS12 pin is less than 1 mA. Following is an example on calculating OCP for the 12-V rail: RI = V(RI)/I(ref) = 1.15 V/20 µA = 56 kΩ 6 Submit Documentation Feedback Copyright © 2001–2010, Texas Instruments Incorporated Product Folder Link(s): TPS3513 |
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