FAN7585SN Fairchild Semiconductor, FAN7585SN Datasheet - Page 13

• Manufacturer Part Number: FAN7585SN
• Description: IC PWM INTELL VOLT MODE 24SDIP
• Manufacturer: Fairchild Semiconductor

Specifications of FAN7585SN

• Pwm Type: Voltage Mode
• Frequency - Max: 9.4kHz
• Duty Cycle: 50%
• Voltage - Supply: 15 V ~ 30 V
• Buck: No
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Operating Temperature: -25°C ~ 85°C
• Package / Case: 24-SDIP (0.300", 7.62mm)
• Frequency-max: 9.4kHz
• Number Of Outputs: Dual Output
• Topology: Push-Pull
• Output Voltage: 40 V
• Output Current: 200 mA
• Switching Frequency: 9.4 KHz
• Operating Supply Voltage: 6.3 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 25 C
• Fall Time: 50 ns
• Mounting Style: Through Hole
• Rise Time: 100 ns
• Synchronous Pin: No
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Number Of Outputs: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

5. Power Good Signal Generator
Power Good Signal Generator circuit generates "ON or OFF" signal depending on the status of output voltage to prevent the
malfunctions of following systems like microprocessor, etc. caused by the output instability at power on or off .
At power on, it produces PG "High" signal after some delay time(about 260ms with C
age. At power off, it produces PG "Low" signal without delay time by sensing the status of power source for protecting follow-
ing systems. Vcc detection point(Pin9) can be calculated by following equation. Recommended values of R11, R12 are
determined by the following equation.
The COMP3 creates PG "Low" without delay when +5V output falls to less than 4.0V to prevent some malfunction at transient
status, thus it improves system stability.
When Remote On/Off signal is high, it generates PG "Low" signal without delay. It means that PG becomes "Low" before
main power is grounded.
PG delay time(T
euqation is as following.
Considering the lightning surge and noise, there are two types of protections. One is a few time delay between TPG and PG for
safe operation and another is some noise margin of Pin10.
Noise_Margin_of_T
T
PG
DET
=
C
---------------------------- -
TPG
=
Ichg
1.25V
×
∆V
PG
×
≈
) is determined by capacitor value(C


PG
C
------------------------------
1
TPG
+
= V
Ichg
R11
---------- -
R12
×
Pin10
Vcc


Vth
4.7kΩ
=
DET
R12
(max)- Vth(L) = 2.9V - 0.6V = 2.3V
=
17.2V
9
2.2uF 1.8V
---------------------------------- -
60kΩ
R11
15uA
×
R13
R14
1.25V
≈
COMP2
260msec
Vref
Vref
COMP1
TPG
), threshold voltage of COMP3 and the charging current and its
ON/OFF
Remote
Q2
PG COMP
Ichg
10
C
2.2 uF
T
PG
0.6V
PG
COMP3
1.8V
Vref
12
TPG
+5V
=2.2uF) for stabilizing output volt-
16
Q3
R15
1 kΩ
PG
11
FAN7585
13