feature

239 ; PC power output monitoring circuit, few external components 3.3V, 5V and 12V overvoltage protection (Vcc) output 3.3V, 5V and 12V undervoltage protection (Vcc) output with delay time

Fault Protected Output with Open Drain Output Open Drain Power Output Good I300ms Power Good Delay ï38ms PSON On/Off Debounce Il $73, ï2.3ms PSON to FPO Turn Off Delay PSON Controlled Latch Function and Protection Input Typical Applications :ïPC Power Supply Vitello Fan 7680 has +3.3V, +5V OVP function, +12V (Vcc) output. The module consists of three comparators, two inputs and a resistor divider. One input comparator is connected to a reference voltage and the other input is connected to a resistive voltage divider. UV Fan 7680 also has +3.3V, +5V UVP function, +12V (Vcc) output. The module consists of three comparators, two inputs and a resistor divider. One input comparator is connected to a reference voltage and the other input is connected to a resistive voltage divider. The PSON Remote On/Off (PSON) section is used to control the outside of the SMPS. When a high signal is applied to the PSON input, the FPO signal becomes a high state, and all the secondary outputs are grounded. Transmitting remote on/off signals has some on/off debuffering time.

illustrate

The FAN7680 is a complete output supervisory circuit for switch-mode secondary-side power supplies. It provides over voltage protection (OVP), under voltage protection (UVP), fault protected output (FPO), remote on/off (PSON), latch, internal delay circuit and provides a good signal generator to monitor the switching power supply system's output. As for output including control, power good output (PGO) and fail safe output (FPO). It directly senses all output rails for OVP and UVP without external dividers. The FAN 7680 provides a simple and cost-effective solution to the external component count and greatly reduces PCB power board space

FPO (fault protection output) is an indicator to judge the system fault condition according to the protection signal. When a fault condition occurs, the FPO signal goes high and the PGO signal goes low, and the main power is turned off. Normal state; "low" fault state; "high" PGO's well-powered signal generator is based on the voltage conditions that output the power supply for the safe operation of the secondary system. A well-powered output should turn off the input power switch in a low state before the output voltage goes out of tune. normal state; "high" fault state; low

Electrical Characteristics

(VCC=5V, Ta=25°C, unless otherwise specified) Over voltage protection, under voltage protection and FPO

Notice:

1. The VCC conversion rate must be less than 14V/ms.

2. Unless otherwise specified, all voltages are measured with respect to the ground pin.

3. Absolute Maximum Ratings indicate that damage to the device may occur if exceeded. Recommended operating conditions represent the conditions under which the device will operate, but do not guarantee specific performance limits.

4. This parameter, although guaranteed to exceed timing characteristics, is not 100% tested in production.

Chronograph

1) AC input on/off - normal state

-Vcc: Supply voltage

-POR: power-on reset

-switch

-FPO: Failsafe output

- Good power input

- Output: output voltage

-Power output

application information

Power Good (PGO) and Power Good Delay PC power supplies are generally designed to provide a power good signal to the motherboard, as defined by the computer manufacturer. If the +3.3V, +5V, and +12V outputs are above the undervoltage threshold limit, the PC power supply delays the power good signal high. At this point the power supply should be able to provide enough power to ensure continuous operation within specifications. Conversely, the PGO signal will be low when one of the +3.3V, +5V, or +12V outputs is below the undervoltage threshold or above the overvoltage threshold, or when the main power is off for long enough that power operation is no longer guaranteed state. The AC input, power good (PGO), remote on/off (PSON), and +3.3V/+5V/+12V rails are shown in Figure 1.

Although no specific timing parameters are required, the following signal timings are recommended:

-T1 (power-on time): T1<500ms

-T2 (rise time): 0.1 ms≤T2≤20 ms

-T3 (PGO delay): 100ms

-T4 (PGO delayed rise time): T4≤10ms

-T5 (AC loss to PGO hold time): T5≥16ms

-T6 (power down warning): T6≥1ms

Additionally, the motherboard should be designed to meet the above suggested timeframes. If timings other than these are implemented or required, this information should be clearly specified. The Fan 7680 has +3.3V, +5V and +12V (Vcc) supply rails and separate Power Good Inputs (PGI). An internal delay circuit is used to generate a power good delay of 300ms. If the voltages at PGI (+1.2V), VS33 (+3.3V), VS5 (+5V), and Vcc (+12V) are above the undervoltage threshold, the open-drain is open-drain when the PGI voltage or +3.3V, +5V and When either of the +12V rails, the Power Good Output (PGO) will go high below the undervoltage threshold after a 300ms delay, the PGO signal will be disabled immediately

Power Remote On/Off (PSON) and Fail-Safe Output (FPO) As the latest generation of PCs focus on easy-on and power-saving features, PC power supplies will require two features. One is the DC power remote on/off function; the other is the power consumption of the PC power supply when the standby voltage reaches very low. Therefore, the main power needs to be turned off. Power Remote On/Off (PSON) is an active low signal that turns on all main power rails, including the +3.3V, +5V and +12V rails. When the PC motherboard holds this signal high or left open, the fault signal protection output (FPO) also goes high. Therefore, the main power rail cannot supply power and remains at 0V. When the FPO signal is held high due to a fault, the fault state will be latched and the mains output rail cannot be powered and remains at 0V. Toggling the PSO input signal from low to high will reset the failsafe latch. Under this fault condition, only the backup power supply is not affected. The 38ms debounce block will be activated when the PSON input signal goes high-to-low or low-to-high to avoid glitches on the PSON input that might disable/enable the FPO output. When PSON is set low, the undervoltage function is disabled for 75ms to avoid power-on failure. When turned off, there is an additional 2.3ms delay from PSON to FPO. The rail should be powered only when the PSON signal is held at ground potential, so the FPO goes low after a 38ms denoised state. The FPO pin can be tied to +5V (or up to +15V) through a pull-up resistor.

Undervoltage protection

The FAN7680 provides under-voltage protection (UVP) for the +3.3V, +5V, and +12V rails. When the voltage is too low when one of the VS33 (+3.3V), VS5 (+5V) Vcc (+12V) input pins exceeds 73U, the PGO will go low and the FPO output will go high. Additionally, this fault state will be latched until PSON switches from low to high or Vcc drops below the minimum operating voltage. When power is turned on by AC input or PSON, the internal UVP delay is 75ms. But under normal conditions, the UVP delay time is a de-ounce time of 73us. In the design of off-line switching power supply systems, the need for undervoltage protection is often ignored. But in battery powered or handheld devices, due to TTL or CMOS logic often failures under medium wave UV conditions. Over Voltage Protection (OVP) Fan 7680's Over Voltage Protection (OVP) monitors +3.3V, +5V and +12V (sense to +12V output pin via Vcc). When the voltage on one of the +3.3V, +5V or +12V input pins exceeds 73us, the FPO output rises and the PGO falls. Additionally, this fault state will be latched until PSON switches from low to high or Vcc falls below the minimum operating voltage. Under fault conditions, most power supplies have the potential to provide a higher output voltage than is normally specified or required. In unprotected equipment, the output voltage may be high enough to cause internal or external damage to the system. It is a common practice to provide overvoltage protection within the power supply in order to protect the system under these abnormal conditions. Since TTL and CMOS circuits are highly susceptible to overvoltage, it has become an industry standard to provide overvoltage protection on all +3.3V, +5V and +12V outputs. Therefore, it is not only necessary to protect the +3.3V and +5V rails of the logic circuit of the motherboard, but also +12V peripherals such as hard disks, floppy disks, and CD-ROM players, etc., need to be protected.