2002 Fairchild Semiconductor Corporation
www.fairchildsemi.com
Rev. 1.0.2
Features
Few External Components
Low Voltage Operation (Vcc_min=4.5V)
Over Voltage Protection for 3.3V/5V/12V Output
Two Protection Inputs (PT1, PT2)
Fault Protection Output with Open Collector
Power Supply on/off Delay Time Control (PSON)
Latch Function Controlled by PSON and Protection
Power Good Signal Generator with Hysteresis
300ms(Typ) Power Good Delay
Programmable Shunt Regulator Trimmed to 2%
16-Pin Dual In-line Package (16-DIP-300)
Description
The FAN3506 is complete housekeeping circuitry for use in
the secondary side of PC SMPS (Switched Mode Power
Supply). It contains various functions, which are over
voltage protection including two extra protection inputs,
power supply on/off delay control and power good signal
generator. Especially, it contains a programmable shunt
regulator for output feedback and the reference voltage is
trimmed to 2%. The FAN3506 is available in 16-DIP.
16-DIP
1
Block Diagram
1
2
3
5
13
14
7
8
6
11
12
10
16
15
9
4
V
CC
FPO
PG
IK
VREF
TPG
GND
PGI
Rd
TPSON
PSON
PT2
PT1
V33
V5
V12
V
CC
V
CC
V
CC
V
CC
V
CC
V
CC
R1
R3
R5
R2
R4
R6
1.26V
+
+
+
+
+_
S
R
Q
Q1
R7 R9 R11
R8
R10 R12
1.32V~1.26V
COMP4
V
CC
lchg
3.9V
Q2
COMP6
1.8V~1.2V
Q3
COMP5
1.32V~1.26V
1.26V
COMP3
1.8V~0.6V
lon
COMP2
1.4V
3.2V
lil
loff
+
_
_
+
+
_
_
+
_
_
_
+
V
CC
_
+
FAN3506
PC SMPS Secondary Side Control IC
FAN3506
2
Pin Description
No
Name
I/O
Function
1
V33
I
+3.3V Output Voltage of SMPS Secondary Side
2
V5
I
+5V Output Voltage of SMPS Secondary Side
3
V12
I
+12V Output Voltage of SMPS Secondary Side
4
V
CC
I
Supply Voltage. +5Vsb(+5V Standby Supply) is Recommended for Vcc.
The Operating Range is 4.5V~15V. Vcc=5V, Ta=25
C at test.
5
FPO
O
Fault Protection Output(FPO) With Open Collector Structure. This Signal Controls the
Primary Switch(PWM IC) Through an Opto-coupler. Maximum Current Rating is 20mA.
When FPO = "Low", the Main SMPS is Operational and if FPO = "High", the Main SMPS
is Turned-off.
6
Rd
-
OFF Delay Resistor. This Block is Made up of a Buffer With Vout = 1.258V. A Resistor
Should be Connected to the Pin6 for Determination of Off Delay Current. The
Recommended Value of Rd Resistor is 28k
at Ctpson=0.22uF. The off Delay Time is
Gotten by Following Equation. Toff = [ Ctpson * (V8max-VthL) ] / (1.258V/Rrd)
7
PSON
I
Power Supply On/Off (Remote On/Off) Input. It is TTL Operation and its Threshold
Voltage is 1.4V. The Maximum Voltage of Pin7 is About 3.9V(Typ), With ABsolutely
Maximum Voltage, 5.25v. If Pson Is Low, Fpo Is Low, Too. That Means The main SMPS
is Operation(Active). When PSON is High, then FPO is High and the Main SMPS is off.
8
TPSON
-
Power Supply On/Off Delay. Ton/Toff = 24ms/8ms(Typ) with Ctpson=0.22uF &
Rd=28k
. Its High/Low Threshold Voltages 1.8V/0.6V and the Maximum Voltage After
Full Charging is About 2.2V. So Vcharge = VthH = 1.8V and Vdischg = V8max - VthL =
1.6V.
Each Delay Time is Decided by the Following Equations, Ton = (Ctpson*VthH) / Ion, Toff
= [Ctpson*(V8max-VthL)] / (Vrd/Rrd) .
9
PG
O
Power Good Signal Output with Open Collector. The Maximum Current Rating is 20mA.
PG High Means that the Power is Good for Operation and PG low Means Power Fail.
10
TPG
-
PG Delay. Td = 300ms(Typ) with Ctpg=2.2uF. The Threshold Voltage is 1.8V and the
Delay Time is Decided by the Following Equation, Td = (Ctpg * Vth) / Ichg = 1.8Ctpg /
Ichg.
11
PGI
I
Power Good Signal Input. Its Threshold Voltage is 1.26V When the PGI Voltage Drops
From High to Low.
12
GND
-
Ground
13
PT1
I
Protection Input 1. This can be Used for an Adjustable OVP or Another Protection Input.
14
PT2
I
Protection Input 2. This can be Used for an Adjustable OVP or Another Protection Input.
15
IK
I
Cathode of the Programmable Shunt Regulator. Absolute Min/Max Current Rating is
1mA/30mA.
16
V
REF
I
Reference of Programmable Shunt Regulator. This Circuit is Prepared for Feedback of
Output Voltage as it Equals to KA431(LM431). It is Trimmed to 2%.
FAN3506
3
Absolute Maximum Ratings
Electrical Characteristics
(V
CC
= 5V, T
a
= 25
C, unless otherwise specified)
Parameter
Symbol
Value
Unit
Supply Voltage
V
CC
4.5 ~ 15
V
FPO (Fault Protection Output) Voltage
VFPO
20
V
FPO Maximum Current
IFPO
20
mA
PGI Maximum Voltage
Vpgi
20
V
PG Output Maximum Current
Io(PG)
20
mA
Cathode Voltage
Vka
20
V
Cathode Current for IK
IK
1 ~ 30
mA
Power Dissipation
P
D
1
W
Operating Temperature Range
T
OPR
-25 ~ +80
C
Storage Temperature
T
STG
-65 ~ +150
C
Parameter
Symbol
Test Conditions
Min.
Typ. Max.
Unit
PROTECTION SECTION
OVP Detecting Voltage for 3.3V
V
OVP
33
PSON=0V
3.9
4.1
4.3
V
OVP Detecting Voltage for 5V
V
OVP
5
PSON=0V
5.7
6.1
6.5
V
OVP Detecting Voltage for 12V
V
OVP
12
PSON=0V
13.6
14.3
15.0
V
Protection Input Voltage 1
V
pt
1
PSON=0V
1.21
1.26
1.31
V
Protection Input Voltage 2
V
pt
2
PSON=0V
1.21
1.26
1.31
V
POWER SUPPLY ON/OFF SECTION (PSON)
PSON Input Threshold Voltage
V
th
PSON=0V : 0V to 2V
1
1.4
1.8
V
PSON Input Open Voltage
V
ih
PSON : Open
2
-
5.25
V
PSON Input Low Current
lil
PSON=0V
0
-
-1
mA
PSON Delay Charging Current
lon
PSON=TPSON=0V
-10
-16
-24
uA
Buffer Output Voltage
VRd
lsink=45uA, 200uA
1.21
1.26
1.31
V
Pin8 Clamping Voltage
V
8max
PSON=0V
2.0
2.2
2.4
V
High Threshold for On/Off Delay (Note1)
VthH
TPSON : 0V to 2.2V
1.6
1.8
2.0
V
Low Threshold for On/Off Delay (Note2)
VthL
TPSON : 2.2V to 0V
0.4
0.6
0.8
V
Power Supply ON Delay Time (Note3)
Ton
Cpin8=0.22
F, Rd=28k
16
26
36
msec
Power Supply OFF Delay Time (Note4)
Toff
Cpin8=0.22
F, Rd=28k
4
8
14
msec
FPO Saturation Voltage
V
sat
(FPO)
lo=10mA
-
0.2
0.4
V
FPO Leakage Current
lleak(FPO)
FPO=20V
0
0.01
1
uA
FAN3506
4
Electrical Characteristics
(Continued)
(V
CC
= 5V, T
a
= 25
C, unless otherwise specified)
Note :
1. Power Supply ON Delay (PSON :High
Low). Power Supply is Active when PSON is Low.
2. Power Supply OFF Delay (PSON :Low
High). Power Supply is Off when PSON is High.
3. Ton = (Cpin8 * Von) / lon = (Cpin8 * VthH) / lon
4. Toff = (Cpin8 * Voff) / loff = [Cpin8 * (V8max - VthL)] / (VRd / Rd)
5,6,7,8 : These parameters, although guaranteed, are but not 100% tested in production.
Parameter
Symbol
Test Conditions
Min.
Typ. Max.
Unit
POWER GOOD SECTION
PGI Threshold Voltage
V
pgi
PGI : 1.5V to 1V
1.21
1.26
1.31
V
V33 Under Voltage Level
V
uv
33
V33 : 3.3V to 2V
2.66
2.8
2.94
V
V5 Under Voltage Level
V
uv
5
V5 : 5V to 3.5V
4.1
4.3
4.5
V
V12 Under Voltage Level
V
uv
12
V12 : 12V to 9V
9.8
10.3
10.8
V
Pin10 Clamping Voltage
V10
max
TPG : Open
3.4
3.9
4.4
V
PG Delay Comparator Threshold Voltage
Vth(TPG)
TPG : 0V to 2.5V
1.5
1.8
2.1
V
PG Delay Comparator Hysteresis Voltage
HY
TPG : 2.5V to 0V
0.3
0.6
0.9
V
Charging Current for PG Delay
lchg
TPG = 0V
-9
-15
-23
uA
PG Delay Time
Td(PG)
Cpin10 = 2.2uF
100
300
500
msec
PG Output Rising Time (Note5)
Tr
Cpin9 = 0.1uF
-
1
-
usec
PG Output Falling Time (Note6)
Tf
Cpin9 = 0.1uF
-
1
-
usec
PG Output Saturation Voltage
Vsat(PG)
lsink = 15mA
-
0.2
0.4
V
PG Output Leakage Current
lleak(PG)
V(PG) = 20V
0
0.01
1
uA
PROGRAMMABLE SHUNT REGULATOR (KA431) SECTION
Reference Input Voltage
V
ref
IK = V
REF
, IK = 1mA
2.45
2.50
2.55
V
Load Regulation
Vref
IK = 1mA to 10mA
-
5
15
mV
Temperature Stability (Note7)
Vref/
T
Ta = -25 ~ +85
C
-
4.5
17
mV
Output Sinking Current Capability
lsink
-
10
25
-
mA
Gain Bandwidth (Note8)
GBW
GV = 1
-
1
-
MHz
TOTAL DEVICE
Supply Current
Icc
PSON = 2V
-
3
8
mA
FAN3506
5
Block Description & Application Hints
1. OVP Block
OVP function is simply realized by connecting Pin1, Pin2, Pin3 to each secondary output. R1,2,3,4,5,6 are internal resistors of
the IC. Each OVP level is determined by resistor ratio and the typical values are 4V/6.1V/14.2V.
- OVP Detecting voltage for +3.3V
. Vovp33 = (R1+R2)/R2 * 1.26V = 4.1V(Typ)
- OVP Detecting voltage for +5V
. Vovp5 = (R3+R4)/R4 * 1.26V = 6.1V(Typ)
- OVP Detecting voltage for +12V
. Vovp12 = (R5+R6)/R6 * 1.26V = 14.3V(Typ)
Especially, Pin13 & Pin14 are prepared for extra OVP inputs or another protection signal, respectively. That is, if you want
over voltage protection of extra output voltage, then you can make a function with two external resistors.
- Threshold Voltage of Protection Input 1 : Vpt1 = 1.26V
- Threshold Voltage of Protection Input 2 : Vpt1 = 1.26V
OVP function operates without delay time. In the case of OVP, system designer should know a fact that the main power can be
dropped after a little time because of system delay, even if FPO is triggered by OVP.
So when the OVP level is tested with a set, you should check the secondary outputs(+3.3V/+5V/+12V) and FPO(Pin5)
simultaneously. you can know the each OVP level as checking each output voltage in just time that FPO is triggered from low
to high.
R1
R3
R5
COMP1
SET of Latch
R2
R4
R6
1.26V
V33
V5
V12
PT1
PT2
VCC
1
2
3
13
14
+
+
+
+
+
_
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