FA5510N Datasheet PDF & Specifications

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FA551 ETC1

Document overview

Manufacturer or author: Provided By www.digicamel.com(FREE DATASHEET DOWNLOAD SITE)
PDF pages: 22

Technical content

■ Block diagram

FA5510P (N), FA5511P (N)
FA5514P (N), FA5515P (N) FA551X series ■ Dimensions, mm
SOP-8 FA5510P (N), FA5511P (N) FA5514P (N), FA5515P (N) ■ Description The FA551X series are the PWM type switching power supply control ICs that can directly drive power MOSFET. These ICs use a CMOS device with high dielectric strength (30V) to implement low power consumption. These ICs contain many function 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
L ow current consumption by CMOS process with high dielectric strength (30V)
Standby current of 2µA or less (at Vcc=14V), and operating current of 1.5mA (typ)
O vervoltage protection function detecting the Vcc voltage
A drive circuit for connecting a power MOSFET directly
Output peak current: ±1.5A
Pulse-by-pulse overcurrent limiting function
O verload protection function (latch or non-latch mode selectable)
Output ON-OFF function by external signal
Latch-mode overvoltage shutdown function
Undervoltage lockout function (16.5V ON / 9V OFF)
Reference voltage output (5V)
8-pin package (DIP/SOP) CMOS IC For Switching Power Supply Control 4.9 3.9 6.0±0.2 0.4±0.1 1.27 0.20 +0.1 –0.05 0~8 1 4 8 5 1.8max
DIP-8 8 5 49.3 6.4 7.62 3.3 4.5max 1.5±0.3 3.0min 0.25 +0.1 –0.05 Type Max. duty Polarity of overcurrent Package cycle (typ.) detection FA5510P 46% + DIP-8 FA5510N SOP-8 FA5511P 70% + DIP-8 FA5511N SOP-8 FA5514P 46% – DIP-8 FA5514N SOP-8 FA5515P 70% – DIP-8 FA5515N SOP-8 0.8V/0.68V 8.5V/7.9V 5V VCC ENB 5V REF 3.5V RT CT OSC +0.24V R S QB Q ENB OUT PUT 16.5V/9V UVLO 15.5V 15.5V 5.2µA 0.95mA PWM 0.8V Dmax FA5510: 46% FA5511: 70% 5V Controlled block FB (2) REF (7) CS(8) VCC(6) OUT (5) GND (4) IS+(3)RT(1) FF 0.8V/0.68V 8.5V/7.9V 5V VCC ENB 5V REF 3.5V RT CT OSC -0.17V R S QB Q ENB OUT PUT 16.5V/9V UVLO 15.5V 15.5V 5.2µA 0.95mA PWM 0.8V Dmax FA5514: 46% FA5515: 70% 5V Controlled block FB (2) REF (7) CS(8) VCC(6) OUT (5) GND (4) IS-(3)RT(1) FF Pin Pin Function Description No. symbol 1R T Oscillator timing Setting oscillation frequency resistor 2F BF eedback Input of PWM comparator 3I SO vercurrent Input of the overcurrent detection limiting function

4 GND Ground Ground

5 OUT Output Output for driving a power

6 VCC Power supply Power supply

7 REF Reference voltage Reference voltage output (5V)

8C S Soft-start and Soft-start, ON/OFF function and ON/OFF control latch-mode shutdown operations

Maximum power dissipation curve ■ Absolute maximum ratings Item Symbol Rating Unit Supply Voltage Low impedance source (I CC >15mA) V CC1 30 V Internal zener clamp (ICC <15mA) V CC2 Self limiting V Output peak current I OUT ±1.5 A FB pin input voltage V FB –0.3 to 5.0 V IS pin input voltage V IS –0.3 to 5.0 V REF pin source current I REF –10 mA CS pin sink current I CS +2.0 mA Total power dissipation (Ta=25˚C) Pd 800 (DIP-8) mW 400 (SOP-8) Ambient temperature Ta –30 to +85 ˚C Maximum junction temperature Tj 125 ˚C Storage temperature Tstg –40 to +150 ˚C Note: There are cases where the IC cannot output the rating current depending on Vcc voltage or temperature. –30 25 85 125 Ambient temperature Ta [˚C] Max. power dissipation 400mW (SOP) 800mW (DIP) ■ Recommended operating conditions Item Symbol Min. Typ. Max. Unit Supply voltage V CC 10 28 V Oscillation frequency f OSC 10 500 kHz REF-GND capacitor Cref 0.1 0.47 µF Soft start capacitor C S 0.01 1 µF

■ Electrical characteristics (VCC =18V, RT=47kΩ, Ta=25˚C) Reference voltage section (REF pin) Item Symbol Test condition Min. Typ. Max. Unit Reference voltage V REF Tj=25˚C 4.75 5.00 5.25 V Line regulation V dv1 VCC =10 to 28V ±6 ±20 mV Load regulation V dv2 IL=0 to 10mA, VCC =18V –40 –12 mV Temperature stability V dT Ta=–30 to 85˚C ±0.5 mV/˚C Oscillator section (RT pin) Item Symbol Test condition Min. Typ. Max. Unit Oscillation frequency f OSC R T=47kΩ, Tj=25˚C 92.6 100 107.4 kHz Voltage stability f dv VCC =10 to 28V ±1.0 % Temperature stability f dT Ta=–30 to 85˚C ±0.02 %/˚C Pulse width modulation circuit section (FB pin) Item Symbol Test condition FA5510/14 FA5511/15 Unit FB pin source current IFB VFB =0 –855 –720 –585 –855 –720 –585 µA Input threshold voltage (FB pin) VTH FB0 Duty cycle =0% 0.9 1 0.9 1 V VTH FBM Duty cycle =DMAX 1.92 2.40 V Maximum duty cycle DMAX 42 46 50 66 70 74 % Overcurrent limiting circuit section (IS pin) Item Symbol Test condition FA5510/11 FA5514/15 Unit Input threshold voltage (IS pin) V THIS 220 240 260 –190 –170 –150 mV Source current (IS pin) I IS VIS=0V ±5 –28 –20 –12 µA Delay time t pdIS 150 150 ns Output ON/OFF control circuit section (CS pin) Item Symbol Test condition Min. Typ. Max. Unit Source current (CS pin) I S0CS VCS =0V, Tj=25˚C –7.2 –5.2 –3.2 µA ON/OFF control threshold voltage (CS pin) V THON OFF →ON, Tj=25˚C 0.8 0.93 V VTHOFF ON →OFF, Tj=25C 0.50 0.68 V Hysteresis voltage V THOHS 0.12 V Soft start circuit section (CS pin) Item Symbol Test condition FA5310/14 FA5311/15 Unit Input threshold voltage (CS pin) VTH CS0 Duty cycle =0% 0.90 1.0 0.90 1.0 V VTH CSM Duty cycle =DMAX 1.92 2.40 V

Overload cutoff circuit section (FB pin) Item Symbol Test condition Min. Typ. Max. Unit Overload threshold voltage (FB pin) V TH FB 3.2 3.5 3.8 V Overvoltage cutoff circuit section (VCC pin) Item Symbol Test condition Min. Typ. Max. Unit Overvoltage threshold voltage (VCC pin) V TH VCC Tj=25˚C 30 31.8 34 V Cutoff operating supply current (VCC pin) I VCC Tj=25˚C, VCC =V THVCC 14 mA Charge current (CS pin) I S0CS2 VCS =6.5V –1.4 –0.95 –0.5 mA Undervoltage lockout circuit section (VCC pin) Item Symbol Test condition Min. Typ. Max. Unit OFF-to-ON threshold voltage V CC ON Tj=25˚C 15.5 16.5 17.5 V ON-to-OFF threshold voltage V CC OFF Tj=25˚C 8.5 9.0 10.0 V Hysteresis voltage V HYS Tj=25˚C 6.8 7.5 8.2 V Output circuit section (OUT pin) Item Symbol Test condition Min. Typ. Max. Unit Low output voltage V OL IOL =100mA 0.7 1.5 V High output voltage V OH IOH =–100mA, VCC =18V 15 16.5 V Rise time tr C L=1nF 40 ns Fall time tf C L=1nF 25 ns Latch-mode cutoff circuit section (CS pin) Item Symbol Test condition Min. Typ. Max. Unit Sink current (CS pin) I SICS VCS =6.5V, VFB =1V, Tj=25˚C 18 30 45 µA Cutoff threshold voltage (CS pin) V TH CSF ON →OFF, Tj=25˚C 8.0 8.5 9.0 V VTH CSN OFF →ON, Tj=25˚C 7.4 7.9 8.4 V Hysteresis voltage V THHIS 0.6 V Supply current (VCC pin) Item Symbol Test condition Min. Typ. Max. Unit Stand-by current I CCSTB VCC =14V 2 µA Startup current I CCST VCC =OFF-to-ON threshold voltage 12 30 µA Operating-state supply current I CCOP No load 1.5 2.5 mA OFF-state supply current I CCOF VCC =17V, CS=0V 80 200 µA Latch mode supply current I CCL VCC =10V 45 80 µA

■ Characteristic curves (VCC =18V, RT=47kΩ, Ta=25˚C) Oscillation frequency (fOSC ) vs. Oscillation frequency (f OSC ) vs. supply voltage (VCC ) timing resistor resistance (RT) Oscillation frequency (fOSC ) vs. FB pin source current (IFB ) vs. FB pin voltage (VFB ) junction temperature (Tj) Maximum duty cycle (DMAX ) vs. timing resitor resistance (RT) Maximum duty cycle (DMAX ) vs. timing resitor resistance (RT) FA5510/14 FA5511/15 100 1000 11 0 100 1000 R T (kΩ) fosc (kHz) 99.9 99.92 99.94 99.96 99.98 100 100.02 100.04 100.06 100.08 100.1 10 15 20 25 30 Vcc (V) fosc (kHz) 98.5 99.5 100 100.5 101 101.5 102 –50 0 50 100 150 Tj (˚C) fosc (kHz) -800 -700 -600 -500 -400 -300 -200 -100 012345 VFB (V) IFB (µA) 11 0 100 1000 R T (kΩ) D MAX (%) 11 0 100 1000 R T (kΩ) D MAX (%)

Maximum duty cycle (DMAX ) vs. junction temperature (Tj) Maximum duty cycle (DMAX ) vs. junction temperature (Tj) FA5510/14 FA5511/15 IS (+) pin current (IIS (+)) vs. IS (+) pin voltage (VIS (+))I S (–) pin current (IIS (–)) vs. IS (–) pin voltage (VIS (–)) FA5510/11 FA5514/15 CS pin current (ICS ) vs. CS pin voltage (VCS )C S pin current (ICS ) vs. CS pin voltage (VCS ) FB=open FB=0V 45.2 45.4 45.6 45.8 46.2 46.4 46.6 46.8 -50 0 50 100 150 Tj (˚C) D MAX (%) 69.2 69.4 69.6 69.8 70.2 70.4 70.6 70.8 -50 0 50 100 150 D MAX (%) Tj (˚C) -0.4 -0.35 -0.3 -0.25 -0.2 -0.15 -0.1 -0.05 -1 0 1 2 3 4 VIS (+) (V) IIS (+) (µA) -25 -20 -15 -10 -1 0 1 2 3 4 VIS (–) (V) IIS (–) (µA) -10 02468 1 0 1 2 VCS (V) ICS (µA) -10 2468 10 12 VCS (V) ICS (µA)

CS pin charge current (ICHG ) vs. junction temperature (Tj) UVLO OFF-to-ON threshold voltage (VCCON ) vs. UVLO ON-to-OFF threshold voltage (V CCOFF ) vs. junction temperature (Tj) junction temperature (Tj) H-level output voltage (VOH ) vs. supply voltage (VCC )L -level output voltage (VOL ) vs. supply voltage (VCC ) IO = –100mA I O =100mA -5.5 -5.3 -5.1 -4.9 -4.7 -4.5 -50 0 50 100 150 Tj (˚C) ICHG (µA) 16.3 16.4 16.5 16.6 16.7 16.8 16.9 -50 0 50 100 150 Tj (˚C) VCCON (V) 8.9 8.95 9.05 9.1 -50 0 50 100 150 Tj (˚C) VCCOFF (V) 0.8 0.9 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 10 15 20 25 30 VCC (V) VCC -VOH (V) 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 10 15 20 25 30 VCC (V) VOL (V)

Operating state supply current (ICCOP ) vs. Operating state supply current (I CCOP ) vs. supply voltage (VCC ) junction temperature (Tj) OFF state supply current (ICCOFF ) vs. supply voltage (VCC ) OFF state supply current (ICCOFF ) vs. supply voltage (VCC ) Enlarged Latch mode supply current (ICCL ) vs. supply voltage (VCC ) Latch mode supply current (ICCL ) vs. supply voltage (VCC ) Enlarged 0.8 0.9 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 10 15 20 25 30 FB=0V FB=Open VCC (V) ICCOP (mA) 1.6 1.62 1.64 1.66 1.68 1.7 1.72 -50 0 50 100 150 FB=0V Tj (˚C) ICCOP (mA) 500 1000 1500 2000 2500 3000 10 15 20 25 30 VCC (V) ICCOFF (µA) 100 120 140 160 180 200 10 12 14 16 18 20 VCC (V) ICCOFF (µA) 500 1000 1500 2000 2500 3000 10 15 20 25 30 VCC (V) ICCL (µA) 100 120 140 160 180 200 10 12 14 16 18 20 VCC (V) ICCL (µA)

■ Description of each circuit 1. Oscillator The oscillator generates a triangular waveform by charging and discharging the built-in capacitor. A desired oscillation frequency can be set by the value of the resistor connected to the RT pin (See Figure 1). The built-in capacitor voltage oscillates between about 3V and 1V, with almost the same charging and discharging gradients (Figure 2). Y ou can set the desired oscillation frequency by changing the gradients using the resistor connected to the RT pin. (Large R T=Low frequency, small RT=High frequency) The relationship between RT and the oscillation frequency is approximately given by: The oscillator waveform cannot be observed from the outside because the oscillator output is not pinned out. The oscillator output is connected to a PWM comparator. 2. PWM comparator The PWM comparator has four inputs as shown in Figure 3. Oscillator output /L54706 is compared with CS pin voltage /L54707, FB pin voltage /L54708, and DT voltage /L54709. The lowest of three inputs /L54707, /L54708, and /L54709 has priority and is compared with oscillator output /L54706. While the voltage is lower than the oscillator output, the comparator output is high. While the voltage is higher than the oscillator output, the PWM comparator output is low (see Figure 4). The IC OUT pin voltage is high while the PWM comparator output is low. When the IC is powered up, CS pin voltage /L54707 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 (FA5510/14: 46%, FA5511/15: 70%) set by DT voltage /L54709 under the condition set by FB pin voltage /L54707, to stabilize the output voltage. Fig. 1 Oscillator Fig. 2 Oscillator output Fig. 3 PWM comparator Fig. 4 PWM comparator timing chart R T RT OSC R T=Small R T=Large /L54709 DT voltage /L54708 FB pin voltage PWM comparator output /L54707 CS pin voltage /L54706 Oscillator output /L54708FB pin voltage PWM comparator output (4.0V) OUT pin voltage /L54709DT voltage /L54706Oscillator output /L54707CS pin voltage fOSC :Oscillation frequency [kHz] RT: Timing resistance [kΩ] fOSC /H113404880 [kHz]R T + 1.4 R T /H113404880 – 1.4 [kΩ]fOSC

Fig. 8 Soft start timing chart Fig. 7 Soft start circuit Fig. 6 CS pin waveform Fig. 5 CS pin circuit 3. CS pin circuit As shown in Figure 5, capacitor Cs is connected to the CS pin. The CS pin voltage varies depending on the charging voltage of this capacitor Cs. When the power is turned on, the constant current source (5.2µA) begins to charge capacitor. Accordingly, the CS pin voltage rises as shown in Figure 6. The CS pin voltage is connected to the PWM comparator, which is characterized to make output based on the lowest of input voltages. The device enters soft-start mode while the CS pin voltage is between 1.0V and V THCSM (FA5510/14: 1.92V, FA5511/15: 2.4V). During normal operation, the CS pin is clamped at 4.0V by internal zener diode. If the output voltage drops due to an overload and the FB voltage rises to 3.5V or more, the clamp voltage 4.0V is canceled and the CS pin voltage rises to 9.5V. The CS pin is also connected to latch comparator C2. If the CS pin voltage rises to 8.5V or more, comparator C2 toggles to turn off the 5V REF circuit, thereby shutting the output down. Since the CS pin is also connected to comparator C1, the 5V REF circuit can be turned off to shut the output down by dropping the CS pin voltage below 0.68V. In this way, comparator C1 can be used for output on-off control. As explained above, the CS pin can be used for soft-start, overload output shutdown, and output on-off control by varying the voltage. Further details on the above three major functions of the CS pin are given below.

3.1 Soft start function

Figure 7 shows the soft start circuit. Figure 8 is a soft-start operation timing chart. The CS pin is connected to capacitor Cs. When the power is turned on, the constant current source (5.2µA) begins to charge the capacitor. As shown in the timing chart, the CS pin voltage rises slowly in accordance with the capacitor Cs charging current. The CS pin is also connected to the IC internal PWM comparator, which has such characteristics that the voltage is determined to output on the basis of the lowest of input voltages. The comparator output pulse slowly widens to cause a soft start as shown in the timing chart. The soft start period can be approximately estimated by the period t S, from the time the IC is activated to the time the output pulse width widens to 30%. The period tS is given by the following equation: PWM Output circuit UVLO REF RT CS FB VCC OSC 5V VCC ENB 5V REF 0.8/0.68V 8.5/7.9V 5.2µA DMAX Cs C33.5V 8 6 9.5 8.5 4.0 VTHCSM 1.0 0.68/0.8 CS pin voltage Vcs [V] OFF mode Soft start Momentary overload or overvoltage Overload or overvoltage Shutdown Time t OUT pin output CS pin voltage DT voltage Oscillator output FB pin voltage VCCCS Cs FB RT OSC PWM DMAX 5.2µA Output circuit Cs: Soft start capacitor [µF] tS [ms] /H11340 310 /H11003 CS [ms]

3.2 Overload shutdown function

Figure 9 shows the overload shutdown circuit, and Figure 10 is a timing chart that illustrates overload shutdown operation. If the output voltage drops due to an overload or short circuit, the FB pin output voltage rises. If the FB pin voltage exceeds the reference voltage (3.5V) of comparator C3, the output of comparator C3 goes low to turn off the switch. With the switch off, the CS pin voltage clamped at 4.0V by zener diode in normal operation is unclamped, and the constant current source (5.2µA) begins to charge capacitor Cs again and the CS pin voltage rises. When the CS pin voltage exceeds the reference voltage (8.5V) of comparator C2, the output of comparator C2 toggles to turn off the 5V REF circuit. The IC then enters the latched mode and shuts down the output. IC current consumption for shutdown is 45µA (typ) (Vcc=10V). This current must be supplied through the startup resistor. The IC enters output off (low voltage) state. The overload shutdown operation can be reset by lowering the supply voltage Vcc to below the OFF threshold voltage (9.0V) or forcing the CS pin voltage below 7.9V. The period t OL from the time the output is short-circuited to the time the output circuit goes off is given by the following equation: When you want to disable the overload shutdown function, see item 9 in “Design advice”

3.3 Output ON/OFF control function

The IC can be turned on or off via an external signal applied to the CS pin. Figure 11 shows the output on/off control circuit, and Figure 12 is a timing chart. The IC is turned off when the CS pin voltage is externally made to drop below 0.68V (typ). The output of comparator C1 goes high to turn the 5V REF circuit off. This shuts the output down. The IC enters output off (low voltage) state. Required IC current consumption during shutdown is 80µA (typ) (Vcc=17V). This current must be supplied through the startup resistor. The IC goes on when the CS pin is opened and the CS pin voltage exceeds 0.80V (typ). This turns the 5V REF circuit on and results in automatic soft start. The power supply then restarts operation. Fig. 9 Overload shutdown circuit PWM Output circuit UVLO REF RT CS FB VCC OSC 5V VCC ENB 5V REF 0.8/0.68V 8.5/7.9V 5.2µA DMAX Cs C33.5V 8 6 Comparator C2 reference voltage (8.5V) CS pin voltage DT voltage Oscillator output OUT pin voltage REF pin voltage FB pin voltage (4V) (9.5V) H L ON OFF Overload detection Overload shutdown (0V) Fig. 10 Overload shutdown timing chart Fig. 11 External output ON/OFF control circuit Fig. 12 Output ON/OFF control circuit timing chart PWM Output circuit UVLO REF RT CS FB VCC OSC 5V VCC ENB 5V REF 0.8/0.68V 8.5/7.9V 5.2µA DMAX Cs 8 6 ON/OFF control CS pin voltage DT voltage Oscillator output OUT pin output REF pin voltage FB pin voltage (4V) H L ON OFF ON mode OFF mode Comparator C1 reference voltage (0.8/0.68V) Cs: Soft start capacitor [µF] tOL [ms] /H11340 870 /H11003 CS [ms]

The IC incorporates a circuit that prevents the IC from malfunctioning when the supply voltage drops. When the supply voltage is raised from 0V, the IC starts operation with Vcc=16.5V (typ). If the supply voltage drops, the output is shut down when Vcc=9.0V (typ). When the undervoltage lockout circuit operates, the outputs of the OUT and CS pins go low to reset the IC. 7. Output circuit The IC contains a push-pull output stage and can directly drive the MOSFET. The absolute maximum rating of OUT pin peak current is ±1.5A. But when using in actual circuit, the output peak current depends on the characteristics of the MOSFET, resistance between the OUT pin and the MOSFET, supply voltage, temperature and so. When supply voltage is relatively low or temperature is relatively high, the output peak current may not reach the maximum ratings. Note that the output current causes loss of the output stage. The total loss caused by the operating current and the output current should be within the ratings in actual circuit.

Fig. 18 Startup circuit (1) MOSFET FA551X DB AC INPUT RsOUT VCC R1: Startup resistance [kΩ] Vac: Effective value of AC input voltage [V] ■ Design advice 1. Deciding the startup circuit These ICs, which use CMOS process, consume less current, and therefore can use larger startup resistance than the conventional bipolar type of IC. To decide the startup resistance, the following conditions must be satisfied: (a) The IC is started when the power is turned on. (b) The IC consumption current is supplied during latch mode operation to maintain the latch state. (c) The IC consumption current is supplied during the off state under the on/off function to maintain the off state. However, these are the minimum conditions for using the IC. The startup time required for the power supply must also be decided on.

1.1 Connecting the startup resistor before rectification

(AC line) When the startup resistor is connected before rectification (AC line) as shown in Figure 18, the voltage applied to the startup resistor forms a half-wave rectified waveform of the AC input voltage. Startup resistor R1 must satisfy the three equations shown below. Select a smaller-side value for R1 in consideration of the temperature characteristics. (a) To supply startup current 30µA at ON threshold voltage 17.5V (max.) of UVLO: (b) To supply IC consumption current 80µA (max.) (Vcc=10V) in latch mode: (c) To supply IC consumption current 200µA (max.) (Vcc=17V) in the off state under the on/off function: If neither the latch mode operation nor the on/off functions are used, only the expression in (5) needs to be satisfied. In this method, the supply current to the IC via the start-up resistor is stopped when AC input is shut down. Therefore, after latch mode operation, shutting the AC input down resets the latch mode in a very short period of time. /L50520/L50749/L507492 R1 /H11021π /H11003 Vac – 17.5 0.03 0.08 /L50520/L50749/L507492 0.2 /L50520/L50749/L507492

1.2 Connecting the startup resistor after rectification

(DC line) When the startup resistor is connected after rectification (DC line) as shown in Figure 19, the voltage applied to the startup resistor becomes the peak value of the AC input voltage. Startup resistor R1 must satisfy the three equations shown below. Select a smaller-side value for R1 in consideration of temperature characteristics. (a) To supply startup current 30µA at ON threshold voltage 17.5V (max.) of UVLO: (b) To supply IC consumption current 80µA (max.) (Vcc =10V) in latch mode: (c) To supply IC consumption current 200µA (max.) (Vcc = 17V) in the off state under the on/off function: If neither the latch nor the on/off functions are used, only the expression in (8) needs to be satisfied. In this method, after latch mode operation, smoothing capacitor C1 in the main circuit supplies current to the IC via the startup resistor even if the AC input is shut down. Therefore, some time must elapse before the latch mode is reset. 2. Determining the Vcc capacitor value To properly start the power supply, a certain value is required for the capacitor connected to the VCC pin. Figure 20 shows the Vcc voltage at start-up when a proper value is given to the capacitor. When the input power is turned on, the capacitor connected to the VCC pin is charged via the startup resistor and the voltage increases. The IC is then in standby state and almost no current is consumed. (Icc<2µA) Thereafter, Vcc reaches the ON threshold voltage of UVLO and the IC begins operation. When the IC begins operation to make output, the IC operates based on the voltage from the auxiliary winding. When the IC is just starting up, however, it takes time for the voltage from the auxiliary winding to rise enough, and Vcc drops during this period. Determine the Vcc capacitor value so that Vcc will not drop down to the OFF threshold voltage of UVLO during this period. If the Vcc capacitor value is too small, Vcc will drop to the OFF threshold voltage of UVLO before the auxiliary winding voltage rises enough. If so, Vcc repeatedly goes up and down between the UVLO threshold voltages, and the power supply cannot start up. (Figure 21) Fig. 19 Startup circuit (2) MOSFET FA551X DB AC INPUT RsOUT VCC Fig. 20 Vcc voltage at startup with a adequate capacitor Fig. 21 Vcc voltage at startup with a inadequate capacitor UVLO ON UVLO OFF Vcc Time t Auxiliary winding voltage Vcc must not drop to UVLO OFF. UVLO ON UVLO OFF Vcc Time t 0.08 /L50520/L50749/L50749 0.03 /L50520/L50749/L50749 R1: Startup resistance [kΩ] Vac: Effective value of AC input voltage [V] 0.2 /L50520/L50749/L50749

The startup period The start up period from the time the power is on to the time the IC is turn to on is approximately given by: To shorten the start-up period, the capacitor C2 or resistor R1 should be decreased. But in some case, such as when the load current of the power supply is changed rapidly, you may want to prolong the hold time of the Vcc voltage over the off threshold. In this case the capacitor C2 cannot be decreased and the resistor R1 should be decreased. But loss of the resistor R1 increases. In such case, the circuit shown in Fig. 23 is effective to shorten start-up period without increasing the loss of the resistor R1. The capacitor C2 is decreased to shorten the start-up period and, after the IC starts up, Vcc voltage supplied from C3 to prolong the hold time of the Vcc voltage. The start-up period of this circuit also is approximately given by the expression in (11) 4. Setting soft start period and OFF latch delay independently Figure 24 shows a circuit for setting the soft start period and OFF latch delay independently. In this circuit, capacitance C S determines the soft start period, and capacitance CL determines the OFF latch delay. If the overload shutdown or overvoltage shutdown functions raise the CS pin voltage to around 5V, zener diode Zn becomes conductive to charge capacitor C L. The OFF latch delay can be thus prolonged by capacitance CL. 5. Overvoltage protection using the VCC pin These ICs contain an overvoltage protection function detecting the Vcc voltage using internal ZD (See item 5 in “Description of each circuit”). If Vcc voltage exceed 31.8V, the current of 14mA flows through the internal ZD and the overvoltage protection function operates. After this protection function operates, the IC continues to consume the large current if high voltage continues to be applied to the Vcc pin. Mind that total IC loss does not exceed the rating. If the voltage source applied to Vcc pin has relatively high impedance and cannot supply the current of 14mA, overvoltage protection function does not operate. But the internal ZD maintains the Vcc voltage 32V or less and protects the IC. Where: R1: Startup resistor [Ω] C2: Capacitor between VCC and GND pin [F] Vac: Effective value of AC input voltage [V] Fig. 22 Startup circuit (3) Fig. 23 Startup circuit (4) VCC FA551X C2 C3 D1 D2R1 VCC FA551X D1R1 Fig. 24 Independent setting of soft start period and OFF latch deley FA551X GND CS Cs Zn CL V1= π /L50520/L50749/L50749 ()tstart-up = –C2 /H11003 R1 /H11003 In 1 –16.5

Overvoltage protection using CS pin These ICs contain the overvoltage protection function detecting Vcc voltage. However, the threshold voltage is fixed. Adding a circuit to CS pin enables the overvoltage protection detecting desired voltage.

6.1 Detecting on secondary side

Figure 25 shows the overvoltage shutdown circuit based on the signal from the secondary side. The optocoupler output transistor is connected between the CS and VCC pins. When the output voltage is put in the overvoltage state, the optocoupler output transistor goes on to raise the CS pin voltage via resistor R2. When the CS pin voltage exceeds the reference voltage (8.5V) of internal comparator, the IC enters the OFF latch mode and shuts the output down. The IC consumes current 45µA (typ) (Vcc=10V) in latch mode. This current must be supplied via startup resistor R1. The overvoltage protection circuit can be reset by lowering the supply voltage Vcc to below 9.0V or forcing the CS pin voltage below 7.9V. In normal operation, the CS pin voltage is clamped by the 4V zener diode with maximum sink current 45µA . Therefore, to raise the CS pin voltage to 8.5V or more, 45µA or a higher current needs to be supplied from the optocoupler. Set the current input to the CS pin to 1mA or less.

6.2 Detecting on primary side (detecting Vcc voltage)

To attain overvoltage protection, the CS pin voltage is forcibly raised from outside the IC until it exceeds the reference voltage (8.5V) of the internal comparator C2. When the reference voltage is exceeded, the IC enters latch mode and shuts the output down. Connect a zener diode (ZD) and resistor between the VCC and CS pins as shown in Figure 26. When the Vcc voltage exceeds about ZD voltage +8.5V, the IC enters the OFF latch mode and shuts the output down. If Vcc remains high even after shutdown and current is input to the CS pin, set the current to 1mA or lower. Set the zener voltage of the ZD connected to the CS pin higher than the UVLO ON threshold voltage. Startup is disabled below this voltage. Figure 27 shows another circuit for enabling latch mode shutdown by detecting a desired Vcc voltage using the CS pin. In this circuit, overvoltage shutdown works when the Vcc voltage is about the same as the ZD voltage. For this circuit also, use a ZD voltage higher than the UVLO ON threshold voltage. Set the current flowing into the CS pin to 1mA or lower. 7. Feedback pin circuit Figure 28 gives an example of connection in which a feedback signal is input to the FB pin. If this circuit causes power supply instability, connect R3 and C4 as shown in Figure 28 to decrease the frequency gain. Set R3 between several tens of ohms to several kilohms and C4 between several thousand picofarads to one microfarad. If noise is applied to the FB pin, the output pulses may be lacked or disturbed. In this case, connect a capacitor C5 as shown in Fig. 29 to suppress the noise applied to the FB pin. Set the capacitance of C5 less than 10% of capacitance of C4 and connect C5 as near the IC as possible. Fig. 25 Overvoltage shutdown circuit (1) FA551X GND CSVCCC2 Cs PC Vin C1 Vout ~ + 6 8 CS VCC R2 ZD VCC CS Cs R2 ZD OUT FB PC1R3 FA551X Rs PC1 Vout Shunt regulator OUT FB FA551X Rs GND PC1R3 Fig. 26 Overvoltage shutdown circuit (2) Fig. 27 Overvoltage shutdown circuit (3) Fig. 28 FB pin circuit (1) Fig. 29 FB pin circuit (2)

Simple voltage control on the primary side In a flyback type power supply, the output voltages of the power supply and auxiliary winding voltage are almost proportional to the number of winding turns of the transformer. This characteristic can be used in the circuit shown in Figure 30, where the output voltage can easily be made constant by detecting the auxiliary winding voltage. However, this is an easy output voltage control method, and the output voltage precision and regulation are therefore not as good. To reduce output pulse width completely to 0%, the FB pin voltage must fall below 0.9V and R5 must be set below about 1kΩ from the characteristics of the FB pin voltage and source current. 9. Disabling the overload shutdown function As shown in Figure 31, connect a 10kΩ resistor R6 between the FB pin and the ground. The FB pin voltage then does not rise sufficiently high to reach the shutdown threshold voltage when an overload occurs so that IC does not enter OFF latch mode. Use a 5% or better-precision resistor for R6. Even with this connection, the overvoltage shutdown function is available. 10. Polarities for overcurrent detecting and their characteristics The FA5510/11 uses positive polarity detection for overcurrent limiting (number 3 pin of IS pin) and the FA5514/15 uses negative polarity detection. The characteristics of positive and negative polarity detection are summarized below. Select one in accordance with the circuit used. (See item 4 in “Description of each circuit.”) Positive detection (FA5510/11)

Wiring is easy because the ground can be shared by the main circuit and IC peripherals.
It is easy to correct the current detected as overload against the input voltage. Negative detection (FA5514/15)
The MOSFET drive current does not flow to the current detection resistor and therefore it hardly affects overcurrent detection. 11. Correcting overload detection current (FA5510/11 only) If the power supply output is overloaded, the overcurrent limiting function restricts the output power and the overload shutdown function stops the IC. The output current when an overload occurs varies depending on the input voltage; the higher the input voltage, the more the overload detection current may increase. If any problems occur as a result of the appearance of this symptom, connect resistor R8 between current detection resistor Rs and the IS (+) pin and add resistor R7 for correction as shown in Figure 32. The standard resistance of R8 is several hundred ohms, and that of R7 is from several hundred kilohms to several megohms. Note that the above correction slightly lowers the output current when overload even where the input voltage is low. This correction is available only for the FA5510/11 that uses positive polarity for overcurrent detection. Fig. 30 Simple voltage control circuit FBGND VCC REF FA551X R5 C2 n1 n2C1 Vout 6 7 FB GND FA551X 2 4 10kΩ Fig. 31 Disabling overload shutdown function FA5510/11 IS(+) Rs T1DB AC input Fig. 32 Correction of overload detection current

Preventing malfunction caused by noise Noise applied to each pin may cause malfunction of the IC. If noise causes malfunction, see the notes summarized below and confirm in actual circuit to prevent malfunction.

The IS pin for overcurrent limiting function detects the MOSFET current converted to the voltage. The parasitic capacitor and inductor of the MOSFET, transformer, wiring, etc. cause a noise in switching operation. If this switching noise causes a malfunction of overcurrent limitimg function, insert the RC filter into IS pin as shown in Figure 13 and 14. Connect this capacitor as near the IC as possible to suppress noise effectively.
Connect a noise prevention capacitor (0.1µF or more) to the REF pin that outputs the reference voltage for each component.
If noise is applied to the FB pin, the output pulses may be disturbed. In this case, see item 7 in “Design advice.”
Relatively large noise may occur at the VCC pin because large current flows from VCC pin to drive the MOSFET. Then this noise may cause malfunction of the IC. In addition, the IC may stop operation when Vcc voltage drops below the off threshold voltage by noise. Mind that capacitance and characteristics of the capacitor connected between VCC and GND pin not to allow the large noise at the VCC pin. To prevent malfunction, suppress the noise width below about 0.5µs or less and noise voltage below about ±0.6V or less. 13. Preventing malfunction caused by negative voltage applied to a pin When large negative voltage is applied to each IC pin, a parasitic element in the IC may operate and cause malfunction. Be careful not to allow the voltage applied to each pin to drop below –0.3V. Especially for the OUT pin, voltage oscillation caused after the MOSFET turns off may be applied to the OUT pin via the parasitic capacitance of the MOSFET, causing the negative voltage to be applied to the OUT pin. If the voltage falls below –0.3V, add a Schottky diode between the OUT pin and the ground. The forward voltage of the Schottky diode can suppress the voltage applied to the OUT pin. Use the low forward voltage of the Schottky diode. Similarly, be careful not to cause the voltages at other pins to fall below –0.3V. 14. Gate circuit configuration To adjust switching speeds or prevent oscillation at gate terminals, resistors are normally inserted between the power MOSFET gate terminal to be driven and the OUT pin of the IC. You may prefer to decide on the drive current independently, to turn the MOSFET on and off. If so, connect the MOSFET gate terminal to the OUT pin of the IC as shown in Figure 34. In this circuit, Rg1 and Rg2 restrict the current when the MOSFET is turned on, and only Rg1 restricts the current when it is turned off. Fig. 33 Protection of OUT pin against the negative voltage FA551X GND OUT SBD OUT Rg1 Rg2 5FA551X Fig. 34 Gate circuit

Loss calculation IC loss must be confirmed to use the IC within the ratings. Since it is hard to directly measure IC loss, some examples of calculating approximate IC loss are given below.

15.1 Calculation example 1

Suppose the supply voltage is Vcc, IC current consumption is lccop, the total gate charge of the power MOSFET is Qg, and the switching frequency is f SW . Total IC loss Pd can be calculated by: Pd /H11340 VCC /H11003 (ICCOP + Qg /H11003 fsw) This expression calculates an approximate value of Pd, which is normally a little larger than the actual loss. Since various conditions such as temperature characteristics apply, thoroughly verify the appropriateness of the calculation under all applicable conditions. Example: When Vcc=18V, lccop=2.5mA (max.) is obtained from the specifications. Suppose Qg=80nC and fsw=100kHz. Pd /H11340 18V /H11003 (2.5mA + 80nC /H11003 100kHz) /H11340 189mW

15.2 Calculation example 2

The IC loss consists of the loss caused by operation of the control circuit and the loss caused at the output circuit to drive the power MOSFET.

15.2.1 Loss at the control circuit

The loss caused by operation of the IC control circuit is calculated by the supply voltage and IC current consumption. When the supply voltage is Vcc and IC current consumption is lccop, loss Pop at the control circuit is: Pop = V CC /H11003 ICCOP Example: When Vcc=18, lccop=1.9mA (typ) is obtained from the specifications. The typical IC loss is given by: Pop = 18V /H11003 1.5mA = 27mW

15.2.2 Loss at the output circuit

The output circuit of the IC is a MOSFET push-pull circuit. When the ON resistances of MOSFETs making up the output circuit are Ron and Roff, the resistances can be determined as shown below based on Vcc=18V and Tj = 25˚C obtained from the output characteristics shown in the specifications: Ron = 15Ω (typ), Roff=7Ω (typ) When the total gate charge of the power MOSFET is Qg, the switching frequency is f SW , the supply voltage is Vcc, and gate resistance is Rg, the loss caused at the IC output circuit is given by: OUT VCC GND Qoff Rg Qon Fig. 35 Output Circuit (1) OUT VCC GND Qoff Rg1 Qon Rg2 Fig. 36 Output Circuit (2) ()Pdr = 1 /H11003 18V /H11003 80nC /H11003 100kHz /H1100315Ω + 7Ω 21 0 Ω+15Ω 10Ω+7Ω =72.8mW ()Pdr = 1 /H11003V CC /H11003Qg /H11003fsw/H11003Ron + Roff

2 Rg + Ron Rg + Roff

()Pdr = 1 /H11003VCC /H11003Qg /H11003fsw/H11003Ron + Roff

2 Rg1+Rg2+Ron Rg1+Roff

....(15) When gate resistance differs between ON and OFF as shown in Figure 36, the loss is given by: Example: When Vcc=18V, Qg=80nC, fsw=100kHz, and Rg=10Ω, the typical IC loss is given by:

15.2.3 Total loss

The total loss (Pd) of the IC is the sum of the control circuit loss (Pop) and the output circuit loss (Pdr) calculated previously: Pd = Pop + Pdr Example: The standard IC loss under the conditions used in (1) and (2) above are: Pd = Pop + Pdr = 27mW + 72.8mW = 99.8mW

■ Application circuit

FA5510
FA5511 R102 R101 R102 C114 C103F1 C104 L2 C105 D2 D201 L201 C201 C204 R207 PC1 R206 R205 IC2 C202 R202 R201 R203 C106 R107 IC1 C109 C110 R106 R112 R109 R119 250V/5A 510K 510K 0.47µF 4700p 4700p 200V/1000µF ERA22-10 2SK1938 33kΩ 10Ω 680Ω 0.22µF 0.22µF 33Ω 0.05Ω 47µF ERA91-02 ESAD92M-02 1000pF 150µH 2200µF 0.1µF 0.022µF 2.4kΩ 1kΩ 10kΩ 0.1µF 2.2kΩ 1kΩ 18kΩ C203 FA5510 FG 80 to 144V AC +24V 0 to 8.4A GND PC2 2.2Ω R210 100Ω C207 R209 470Ω R208 1kΩ ZD201 27V TH1 8D11 TH2 8D11D1 D3SBA60C102 0.22µF R103 R104 100kΩ 100kΩ C205 1000pF C206 0.1µF PC2 0.1µF R105 47kΩ R117 2kΩ PC1 C108 1234 5 6 7 8 2200pF 4.7kΩ R110 C115 1000pF C107 R102 R101 R102 C101 C103 F1 C104 L1 C102 DB TH1 C105 ZD1 C113 D201 L201 C202 C204 R207 PC1 R206 R205 IC2 C203 R202 R201 R203 C106 R107 IC1 C109 C110 C108 5D11 R112 R110R109 R108 R103 R104 250V/3A 430K 510K 0.22µF 470p 470p 0.22µF D3SBA60 130kΩ 130kΩ 400V/220µF 180V ERA22-10 2SK2101 4.7kΩ 100Ω 10Ω ERA91-02 680Ω 0.22µF 0.22µF 100pF 0.1Ω 10µF ERA91-02 2200p YG902C 2200µF 10µH 470µF 0.022µF 2.4kΩ 1kΩ 33kΩ 0.1µF 2.2kΩ 1kΩ 18kΩ C201 FA5511 1234 5 6 7 8 FG 80 to 264V AC +24V 0 to 1.46A (Peak:2.71A) GND C107 R106 R105 24Ω 0.1µF 62kΩ 1kΩ R117

FA5514 Parts tolerances characteristics are not defined in the circuit design sample shown above. When designing an actual circuit for a product, you must determine parts tolerances and characteristics for safe and economical operation.
FA5515 R102 R101 R102 C114 C103F1 C104 L2 C105 D2 D201 L201 C201 C204 R207 PC1 R206 R205 IC2 C202 R202 R201 R203 C106 R107 IC1 C109 C110 R106 R112 R109 R119 250V/5A 510K 510K 0.47µF 4700p 4700p 200V/1000µF ERA22-10 2SK1938 33kΩ 10Ω 680Ω 0.22µF 0.22µF 33Ω 0.05Ω 47µF ERA91-02 ESAD92M-02 1000pF 150µH 2200µF 0.1µF 0.022µF 2.4kΩ 1kΩ 10kΩ 0.1µF 2.2kΩ 1kΩ 18kΩ C203 FA5514 FG 80 to 144V AC +24V 0 to 8.4A GND PC2 2.2Ω R210 100Ω C207 R209 470Ω R208 Ω ZD201 27V TH1 8D11 TH2 8D11D1 D3SBA60C102 0.22µF R103 R104 100kΩ 100kΩ C205 1000pF C206 0.1µF PC2 R105 47kΩ C108 2200pF C115 1000pF R117 820Ω PC1 C107 0.1µF R110 4.7kΩ 1234 5 6 7 8 R101 R102 C101 C103 F1 C104 L1 C102 DB TH1 C105 ZD1 C113 D201 L201 C202 C204 R207 PC1 R206 R205 IC2 C203 R202 R201 R203 C106 R107 IC1 C109 C110 C108 C107 R106 R105 5D11 R112 R110R109 R108 R103 R104 250V/3A 430K 510K 0.22µF 470p 470p 0.22µF D3SBA60 130kΩ 130kΩ 400V/220µF 180V ERA22-10 2SK2101 4.7kΩ 100Ω 10Ω ERA91-02 680Ω 0.22µF 0.22µF 100pF 24Ω 0.1µF 62kΩ 0.05Ω 10µF ERA91-02 2200p YG902C 2200µF 10µH 470µF 0.022µF 2.4kΩ 1kΩ 33kΩ 0.1µF 2.2kΩ 1kΩ 18kΩ C201 FA5515 FG 80 to 264V AC +24V 0 to 1.46A (Peak:2.71A) GND 1234 5 6 7 8

Overview

FA5510N is listed in the IC category. Available datasheets include documents from Fuji Electric. DigiCamel provides a local PDF and searchable HTML technical text for online reference.

Summary

CMOS IC For Switching Power Supply Control

Description