CALLM FA5317S, FA5317P, FA5316S, FA5316P, FA5315S Datasheet

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FA531X series

FA5310BP(S), FA5314P(S), FA5316P(S) FA5311BP(S), FA5315P(S), FA5317P(S)

■ Description

The FA531X series are bipolar ICs for switching power supply control that can drive a power MOSFET. These ICs contain many functions in a small 8-pin package. With these ICs, a high-performance and compact power supply can be created because not many external discrete

components are needed.

■ Features

• Drive circuit for connecting a power MOSFET

• Wide operating frequency range (5 to 600kHz)

• Pulse-by-pulse overcurrent limiting function

• Overload cutoff function (Latch or non-protection mode selectable)

• Output ON/OFF control function by external signal

• Overvoltage cutoff function in latch mode

• Undervoltage malfunction prevention function

• Low standby current (90µA typical)

• Exclusive choices by circuits (See selection guide on page 25)

• 8-pin package (DIP/SOP)

■ Applications

• Switching power supply for general equipment

Bipolar IC

For Switching Power Supply Control

■ Dimensions, mm Á SOP-8

6.05

5.3

8.2

±0.3

0.4

±0.1

1.27

±0.2

0.6

0.20

+0.1

–0.05

0~10°

2.0max

Á DIP-8

FA531X series

■ Block diagram

Á FA5310BP(S)/FA5311BP(S)/FA5316P(S)/FA5317P(S)

Á FA5314P(S)/FA5315P(S)

9.3

6.5

7.6

3.4

4.5max

1.5

3.0min

0~15˚

0.5

±0.1

2.54

±0.25

0.3

+0.1

–0.05

Pin Pin Description No. symbol

1 RT Oscillator timing resistor 2 FB Feedback 3 IS (+) Overcurrent (+) detection 4 GND Ground 5 OUT Output 6 VCC Power supply 7 CT Oscillator timing capacitor 8 CS Soft-start and ON/OFF control

Pin Pin Description No. symbol

1 RT Oscillator timing resistor 2 FB Feedback 3 IS (–) Overcurrent (–) detection 4 GND Ground 5 OUT Output 6 VCC Power supply 7 CT Oscillator timing capacitor 8 CS Soft-start and ON/OFF control

FA531X series

■ Selection guide

Type

FA5310BP(S) 46% + 16.0V 8.70V 1.5A Forward type FA5311BP(S) 70% + 16.0V 8.70V 1.5A Flyback type FA5314P(S) 46% – 15.5V 8.40V 1.5A Forward type FA5315P(S) 70% – 15.5V 8.40V 1.5A Flyback type FA5316P(S) 46% + 15.5V 8.40V 1.0A Forward type FA5317P(S) 70% + 15.5V 8.40V 1.0A Flyback type

Max. duty cycle (typ.)

Polarity of overcurrent detection

Max. output current

UVLO (typ.)

Application

ON threshold

OFF threshold

Notes:

Derating factor Ta > 25°C : 8.0mW/°C (on PC board )

Derating factor Ta > 25°C : 5.5mW/°C (on PC board )

■ Absolute maximum ratings

Item Symbol Rating Unit

Supply voltage VCC 31 V Output current

FA5310/11/14/15

IO ±1.5 A

FA5316/17

±1.0

Feedback terminal input voltage

VFB 4V

Overcurrent detection VIS –0.3 to +4 V terminal input voltage

CS terminal input current ICS 2mA Total power dissipation Pd 800 (DIP-8) *

(Ta=25°C) 550 (SOP-8) *

Operating temperature Topr –30 to +85 °C Junction temperature Tj 125 °C Storage temperature Tstg –40 to +150 °C

■ Recommended operating conditions

Item Symbol Min. Max. Unit

Supply voltage VCC 10 30 V Oscillator timing resistance

FA5310/11 RT 3.3 10 kΩ FA5314/15/16/17 1 10

Soft-start capacitor CS 0.1 1

Oscillation frequency fOSC 5 600 kHz

Soft-start circuit section

Item Symbol Test condition FA5310/14/16 FA5311/15/17 Unit

Min. Typ. Max. Min. Typ. Max.

Charge current (Pin 8) ICHG Pin 8=0V –15 –10 –5 –15 –10 –5 µA Input threshold voltage (Pin 8) VTH CSO Duty cycle =0% 0.90 0.90 V

VTH CSM Duty cycle =DMAX 1.90 2.30 V

■ Electrical characteristics (Ta=25°C, Vcc=18V, fOSC=135kHz) Oscillator section

Item Symbol Test condition Min. Typ. Max. Unit

Oscillation frequency fOSC RT=5.1kΩ, CT=360pF 125 135 145 kHz Frequency variation 1 (due to supply voltage change) fdV VCC=10 to 30V ±1% Frequency variation 1 (due to temperature change) fdr Ta=–30 to +85°C ±1.5 %

Pulse width modulation circuit section

Item Symbol Test condition FA5310/14/16 FA5311/15/17 Unit

Min. Typ. Max. Min. Typ. Max.

Feedback terminal source current IFB VFB=0 –660 –800 –960 –660 –800 –960 µA Input threshold voltage (Pin 2) VTH FBO Duty cycle =0% 0.75 0.75 V

VTH FBM Duty cycle =DMAX 1.80 2.30 V

Maximum duty cycle DMAX 43 46 49 66 70 74 %

FA531X series

Overcurrent limiting circuit section

Item Symbol Test condition FA5310/11/16/17 FA5314/15 Unit

Min. Typ. Max. Min. Typ. Max.

Input threshold voltage (Pin 3) VTH IS 0.21 0.24 0.27 –0.21 –0.17 –0.14 V Overcurrent detection terminal source current IIS Pin 3=0V –300 –200 –100 –240 –160 –80 µA Delay time TPD IS 150 200 ns

Latch-mode cutoff circuit section

Item Symbol Test condition Min. Typ. Max. Unit

CS terminal sink current ISINK CS Pin 8=6V, Pin 2=1V 25 45 65 µA Cutoff threshold voltage (Pin 8) VTH CS 6.5 7.0 7.5 V

Overload cutoff circuit section

Item Symbol Test condition Min. Typ. Max. Unit

Cutoff-start voltage (Pin 2) VTH FB 2.6 2.8 3.1 V

Undervoltage lockout circuit section

Item Symbol Test condition FA5310/11 FA5314/15/16/17 Unit

Min. Typ. Max. Min. Typ. Max.

OFF-to-ON threshold voltage VCC ON 15.5 16.0 16.5 14.8 15.5 16.2 V ON-to-OFF threshold voltage VCC OFF 8.20 8.70 9.20 7.70 8.40 9.10 V

Overall device

Item Symbol Test condition Min. Typ. Max. Unit

Standby current ICC ST VCC=14V 90 150 µA Operating-state supply current ICC OP 915mA OFF-state supply current ICC OFF 1.1 1.8 mA Cutoff-state supply current ICCL 1.1 1.8 mA

Output section

Item Symbol Test condition Min. Typ. Max. Unit

FA5310/11/14/15

FA5316/17

L-level output Voltage VOL IO=100mA IO=50mA 1.30 1.80 V H-level output Voltage VOH IO=–100mA IO=–50mA 16.0 16.5 V

VCC=18V VCC=18V

Rise time tr No load No load 50 ns Fall time tf No load No load 50 ns

Output ON/OFF circuit section

Item Symbol Test condition Min. Typ. Max. Unit

CS terminal source current

Isource cs

Pin 8=0V –15 –10 –5 µA

OFF-to-ON threshold Voltage (Pin 8) VTH ON CS terminal voltage OFF→ON 0.56 V ON-to-OFF threshold Voltage (Pin 8) VTH OFF CS terminal voltage ON→OFF 0.42 V

FA531X series

■ Description of each circuit

1. Oscillator (See block diagram)

The oscillator generates a triangular waveform by charging and discharging a capacitor. CT pin voltage oscillates between an upper limit of approx. 3.0V and a lower limit of approx. 1.0V. The oscillation frequency is determined by a external resistance and capacitance shown in figure 1, and

approximately given by the following equation:

The recommended oscillation range is between 5k and 600kHz. The oscillator output is connected to a PWM comparator.

2. Feedback pin circuit

Figure 2 gives an example of connection in which an optocoupler is used to couple the feedback signal to the FB pin. It is designed to be strong against noise and will not create parasitic oscillation so much, because the output impedance at the FB pin is as low as 4k to 5k. If this circuit causes power supply instability, the frequency gain can be decreased by connecting R4 and C4 as shown in figure 2. R4 should be between several tens of ohms to several kiloohms and C

should be between several thousand picofarads to one microfarads.

3. PWM comparator

The PWM comparator has four inputs as shown in Figure 3. Oscillator output ① is compared with CS pin voltage ➁, FB pin voltage ➂, and DT voltage ④. The lowest of three inputs ➁, ➂, and ④ is compared with output ①. If it is lower than the oscillator output, the PWM comparator output is high, and if it is higher than the oscillator output, the PWM comparator output is low (see Fig. 4). The IC output voltage is high during when the comparator output is low, and the IC output voltage is low during when the comparator output is high. When the IC is powered up, CS pin voltage ➁ controls soft start operation. The output pulse then begins to widen gradually. During normal operation, the output pulse width is determined within the maximum duty cycle set by DT voltage ④ under the condition set by feedback signal ➂, to stabilize the output voltage.

f (kH

Z) =

.........(1)

Fig. 1 Oscillator

Fig. 2 Configuration with optocoupler (FB pin input)

Fig. 3 PWM comparator

Fig. 4 PWM comparator timing chart

4RT (kΩ) • CT (pF)

FA531X series

4. CS pin circuit

As shown in Figure 5 capacitor C

S is connected to the CS pin.

When power is turned on, the constant current source (10µA) begins to charge capacitor C

S. Accordingly, the CS pin

voltage rises as shown in Figure 6. The CS pin is connected to an input of the PWM comparator. The device is in soft-start mode while the CS pin voltage is between 0.9V and 1.9V (FA5310/14/16) and between 0.9V and 2.3V(FA5311/15/17). During normal operation, the CS pin is clamped at 3.6V by internal zener diode Zn. If the output voltage drops due to an overload, etc., the clamp voltage shifts from 3.6V to 8.0V. As a result, the CS pin voltage rises to 8.0V. The CS pin is also connected to latch comparator C2. If the pin voltage rises above 7.0V, the output of comparator C2 goes high to turn off the bias circuit, thereby shutting the output down. Comparator C2 can be used not only for shutdown in response to an overload, but also for shutdown in response to an overvoltage. Comparator C1 is also connected to the CS pin, and the bias circuit is turned off and the output is shut down if the CS pin voltage drops below 0.42V. In this way, comparator C1 can also be used for output on/off control. As explained above, the CS pin can be used for soft-start operation, overload and overvoltage output shutdown and output on/off control. Further details on the four functions of the CS pin are given below.

4.1 Soft start function

Figure 7 shows the soft start circuit. Figure 8 is the soft-start operation timing chart. The CS pin is connected to capacitor C

S. When power is turned on, a 10µA constant-current source

begins to charge the capacitor. As shown in the timing chart, the CS pin voltage rises slowly in response to the charging current. The CS pin is connected internally to the PWM comparator. The comparator output pulse slowly widens as shown in the timing chart. The soft start period can be approximately evaluated by the period ts from the time the IC is activated to the time the output pulse width widens to 30%. Period ts is given by the following

equation:

tS(mS)=160CS(µF)...................................(2)

Fig. 5 CS pin circuit

Fig. 6 CS pin waveform

Fig. 7 Soft-start circuit

Fig. 8 Soft-start timing chart

FA531X series

4.2 Overload shutdown

Figure 9 shows the overload shutdown circuit, and Figure 10 is a timing chart which illustrates overload shutdown operation. If the output voltage drops due to an overload or short-circuit, the output voltage of the FB pin rises. If FB pin voltage exceeds the reference voltage (2.8V) of comparator C3, the output of comparator C3 switches low to turn transistor Q off. In normal operation, transistor Q is on and the CS pin is clamped at 3.6V by zener diode Zn. With Q off, the clamp is released and the 10µA constant-current source begins to charge capacitor CS again and the CS pin voltage rises. When the CS pin voltage exceeds the reference voltage (7.0V) of comparator C2, the output of comparator C2 switches high to turn the bias circuit off. The IC then enters the latched mode and shuts the output down. Shutdown current consumption is 400µA(VCC=9V). This current must be supplied through the startup resistor. The IC then discharges the MOSFET gates. Shutdown operation initiated by an overload can be reset by lowering supply voltage V

CC below VCC OFF or forcing the CS

pin voltage below 7.0V. The period t

OL from the time that the output is short-circuited to

the time that the bias circuit turns off is given by the following equation:

OL(mS)=340Cs(µF)........................................... (3)

4.3 Overvoltage shutdown

Figure 11 shows the overvoltage shutdown circuit, and Figure 12 is a timing chart which illustrates overvoltage shutdown operation. The optocoupler PC1 is connected between the CS and V

pins. If the output voltage rises too high, the PC1 turns on to raise the voltage at the CS pin via resistor R

6. When the CS

pin voltage exceeds the reference voltage (7.0V) of comparator C2, comparator C2 switches high to turn the bias circuit off. The IC then enters the latched mode and shuts the output down. The shutdown current consumption of the IC is 400µA(VCC=9V). This current must be applied via startup resistor R

The IC then discharges the MOSFET gates. The shutdown operation initiated by an overvoltage condition can be reset by lowering supply voltage V

CC below VCC OFF or

forcing the CS pin voltage below 7.0V. During normal operation, the CS pin is clamped by a 3.6V zener diode with a sink current of 65µA max. Therefore, a current of 65µA or more must be supplied by the optocoupler

in order to raise the CS pin voltage above 7.0V.

Fig. 9 Overload shutdown circuit

Fig. 10 Overload shutdown timing chart

Fig. 11 Overvoltage shutdown circuit

Fig. 12 Overvoltage shutdown timing chart

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