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PDF FAN7680 Data sheet ( Hoja de datos )
| Número de pieza | FAN7680 | |
| Descripción | PC Power Supply Outputs Monitoring IC | |
| Fabricantes | Fairchild Semiconductor | |
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www.fairchildsemi.com
FAN7680
PC Power Supply Outputs Monitoring IC
Features
• PC Power Supply Output Monitor Circuitry
• Few External Components
• Over Voltage Protection for 3.3V, 5V and 12V(Vcc)
Outputs
• Under Voltage Protection for 3.3V, 5V and 12V(Vcc)
Outputs with Delay Time
• Fault Protection Output with Open Drain Output
• Open Drain Power Good Output
• 300ms Power Good Delay
• 38ms PSON On/Off Debounce
• 73us Debounce
• 2.3ms PSON to FPO Turn Off Delay
• Latch Function Controlled by PSON and Protection
Inputs
Typical Application
• PC Power Supply
Description
The FAN7680 is a complete output supervisory circuitry
intended for use in the secondary side of a switched mode
power supply. It provides over voltage protection (OVP),
under voltage protection (UVP), fault protection output
(FPO), remote On/Off (PSON), latch, internal delay circuits
and power good signal generator to monitor and control the
output of the switching power supply system. As for output
control, power good output(PGO) and fault protection out-
put(FPO) are included. It directly senses all the output rails
for OVP and UVP without external dividers. The FAN7680
offers a simple and cost effective solution with minimum
number of external components and greatly reduces PCB
board space for power supply.
8-DIP
8-SOP
1
1
OVP
The FAN7680 has OVP functions for +3.3V, +5V,
+12V(Vcc) outputs. This block is made up of three compara-
tors with two inputs and resistor dividers. One input of a
comparator is connected to a reference voltage and another
input is connected to a resistor divider.
UVP
The FAN7680 also has UVP functions for +3.3V, +5V,
+12V(Vcc) outputs. This block is made up of three compara-
tors with two inputs and resistor dividers. One input of a
comparator is connected to a reference voltage and another
input is connected to a resistor divider.
PSON
The remote on/off(PSON) section is for controlling the
SMPS externally. When a high signal is applied to the PSON
input, the FPO signal becomes a high state and all secondary
outputs are grounded. The remote on/off signal is transferred
with some on/off debounce time.
FPO
The FPO(Fault Protection Output) is a signal which indicates
the system fault condition according to protection signals.
When a fault state is occured, the FPO signal becomes high
and the PGO signal becomes low and the main power is to be
turned off.
Normal State; "Low"
Fault State; "High"
PGO
The power good signal generator provides a signal according
to output voltage conditions of a power supply for safe oper-
ation of a secondary system. The power good output should
be low state before the output voltage is out of regulation at
turn-off of the input power switch.
Normal State ; "High"
Fault State ; "Low"
©2003 Fairchild Semiconductor Corporation
Rev. 1.0.0
1 page  
FAN7680
Electrical Characteristics
(VCC = 5V, Ta=25°C, unless otherwise specified)
Over Voltage Protection, Under Voltage Protection and FPO
Characteristic
Symbol
Test Condition
Over Voltage Threshold
Under Voltage Threshold
Leakage Current(FPO)
Low Level Output Voltage(FPO)
VS33OV
VS5OV
12V(VCC)OV
VS33UV
VS5UV
12V(VCC)UV
ILKG1
VOLI
VFPO = 5V
Isink=10mA
Isink=30mA
PGI and PGO
Characteristic
Input Threshold Voltage(PGI)
Leakage Current(PGO)
Low Level Output Voltage(PGO)
Symbol
VPGI
ILKG2
VOL2
Test Condition
VPGO = 5V
Isink=10mA
PSON Control
Characteristic
Input Pull-up Current
High-Level Input Voltage
Low-Level Input Voltage
Symbol
Test Condition
VPSON = 0V
Total Device
Characteristic
Supply Current
Symbol
ICC
Test Condition
VPSON = 5V
Min.
3.9
5.8
13.3
2.55
4.1
8.8
-
-
-
Typ.
4.1
6.1
13.8
2.69
4.3
9.3
-
-
-
Max.
4.3
6.4
14.3
2.83
4.5
9.8
5
0.3
0.7
Unit
V
V
uA
V
Min.
1.16
-
-
Typ.
1.20
-
-
Max.
1.24
5
0.4
Unit
V
uA
V
Min.
-
2.4
-
Typ.
150
-
-
Max.
-
-
1.2
Unit
uA
V
V
Min. Typ. Max. Unit
- - 1 mA
Timing Characteristics
(VCC=5V, Ta=25°C, unless otherwise specified)
Characteristic
Symbol
Test Condition
Min. Typ. Max. Unit
Debounce Time(PSON)
Noise Debounce Time
PGO Delay Time(PGI to PGO)
tb1
tb2 Note 4
td1
25 38 51 ms
50 73 100 us
200 300 410 ms
Internal UVP Delay Time
PSON Off to FPO Delay Time
td2
FPO goes low and
every time PGI > 1.20
td3
51 75 102
tb1+1.6 tb1+2.3 tb1+3.2
ms
ms
Note
1. VCC slew rate must be less than 14V/ms.
2. All voltages are measured with respect to the ground pin, unless otherwise specified.
3.The Absolute Maximum Ratings indicate the limits that if exceed, damage to the device may occur. Recommended Operating
Conditions indicate conditions in which the device is functional, but do not guarantee specific performance limits.
4. This parameter, although guaranteed over the Timing Characteristics, is not 100% tested in production.
5
5 Page 
FAN7680
Application Information
Power Good(PGO) and Power Good Delay
A PC power supply is commonly designed to provide the motherboard with a power good signal, which is defined by the com-
puter manufactures. If the +3.3V, +5V, and +12V outputs are above the undervoltage threshold limit, the PC power supply
makes the power good signal high after some delay. At this time the power supply should be able to provide enough power to
assure continuous operation within the specification. Conversely, when one of the +3.3V, +5V, or +12V outputs falls below the
undervoltage threshold or rise above the overvoltage threshold, or when main power has been turned off for a sufficiently long
time so that power supply operation is no longer assured, a PGO signal will be a low state.
The AC input, power good(PGO), remote on/off(PSON), and +3.3V/+5V/+12V supply rails are shown in figure 1.
T1
VAC
PSON
+12VDC
+5VDC
+3.3VDC
95%
10%
PGO
T2
T3
T4
T5
Figure 1. Timing Diagram
T5
Although there is no requirement for specific timing parameters, the following signal timings are recommended :
-T1(Power On Time) : T1 < 500ms
-T2(Rise Time) : 0.1ms ≤ T2 ≤ 20ms
-T3(PGO Delay) : 100ms < T3 <500ms
-T4(PGO Delay Risetime) : T4 ≤ 10ms
-T5(AC Loss to PGO Hold-Up Time) : T5 ≥ 16ms
-T6(Power Down Warning) : T6 ≥ 1ms
Furthermore, motherboards should be designed to comply with the above recommended timing range. If timings other than
these are implemented or required, that information should be clearly specified.
The FAN7680 provides a power good(PGO) signal for the +3.3V, +5V and +12V(Vcc) supply voltage rails and a separate
power good input(PGI). An internal delay circuit is used to generate a 300ms power good delay.
If voltages at PGI(+1.2V), VS33(+3.3V), VS5(+5V), and Vcc(+12V) rise above the undervoltage threshold, the open drain
power good output(PGO) will go high after a delay of 300ms. When the PGI voltage or any of +3.3V, +5V, and +12V rails
drops below the undervoltage threshold, the PGO signal will be disabled immediately.
Power Supply Remote On/Off(PSON) and Fault Protect Output(FPO)
Since the latest personal computer generation focuses on easy turn on and power saving functions, a 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 power supply. 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 +3.3V,
+5V, and +12V 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 can not deliver power and are held at 0V.
When the FPO signal is held high due to an fault condition, the fault status will be latched and the outputs of the main power
rails can not deliver power and are held at 0V. Toggling the PSON input signal from low to high will reset the fault protection
latch. During this fault condition only the standby power is not affected.
When the PSON input signal goes from high to low or low to high, the 38ms debounce block will be active to avoid that a
glitch on the PSON input may disable/enable the FPO output. When the PSON is set low, the undervoltage function is disabled
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet FAN7680.PDF ] | |
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