FA5590 FUJI [Fuji Electric], FA5590 Datasheet - Page 16

• Manufacturer Part Number: FA5590
• Description: FUJI Power Supply Control IC
• Manufacturer: FUJI [Fuji Electric]

Functions
(i) Input of feedback signal of output voltage setting
(ii) Detect short-circuit of FB terminal
(iii) Detect output overvoltage
Application
(i) Feedback signal input
- Wiring
Connect the node between voltage dividing resistors for setting output
voltage.
- Operation
The output voltage Vout of PFC is controlled so that FB voltage matches
the internal reference voltage (2.5V).
To detect FB terminal opening, pull-up current (Ipullup) is supplied to the
FB terminal. This current flows to GND via R2. For this reason,
resistance R1, R2 should be set in consideration of this current when the
output voltage (Vout) is set.
To prevent malfunction due to noise, capacitor C3 of 100pF~3300pF
should be connected between the FB terminal and GND.
(ii) FB terminal short-circuit detection
- Wiring
Same as for the (i) Feedback signal input
- Operation
When the input voltage of the FB terminal becomes 0.3V or lower due to
short-circuit of R2, the output of the comparator (SP) inverts to stop the
output of the IC.
(iii) Output overvoltage detection
- Wiring
Same as for the (i) Feedback signal input
- Operation
Normally the voltage of the FB terminal is 2.5V almost same as the
reference voltage of the error amplifier. When the output voltage rises for
some reason and the voltage of the FB terminal reaches the comparator
reference voltage (1.09*VREF), the output of the comparator (OVP)
inverts to stop the OUT pulse. If the output voltage returns to the normal
value, the OUT pulse resumes.
Function
(i) Phase compensation of internal ERRAMP output
Application
(i) Phase compensation of internal ERRAMP output
- Wiring
Connect C, R between COMP terminal and GND as shown in Fig. 16.
- Operation
Connecting C, R to the COMP terminal suppress ripple component at 2
times the frequency of the AC line that appears in the FB output.
Vout
11. Description of use for each pin
AN-016E Rev.1.2
April-2011
(1) Terminal No. 1 (FB terminal)
VREF : Reference voltage =2.5V(typ)
(2) Terminal No. 2 (COMP terminal)
Ipullup : FB terminal pull-up current =1.8uA(typ)
Fuji Electric Co., Ltd.

(
VREF
/
R
2

Ipullup
)

R
1

VREF
FA5590N,FA5591N
16
R1
R2
http://www.fujielectric.co.jp/products/semiconductor/
Vout
ERRAMP
FB
C3
Fig.16 COMP pin circuit
Fig.15 FB pin circuit
1
1.8uA
PWM.comp
Ｄｙｎａｍｉｃ ＯＶＰ
ERRAMP
ＯＶＰ Ｃｏｍｐ
2
Short Ｃｏｍｐ
COMP
C4
VREF(2.5V)
Vthfb(0.3V)
Vsovp(1.09*VREF)
Vdovp(1.05*VREF)
COMP
RAMP OSC
OVP
SP
R3
C5