FC3255 FCI | Alldatasheet
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Technical content
Features
Integrated Power Switch: 1.5 A Guaranteed Input Voltage Range: 2.7 V to 30 V High Frequency Allows for Small Components Minimum External Components Easy External Synchronization Built in Overcurrent Protection Frequency Foldback Reduces Component Stress During an Overcurrent Condition Thermal Shutdown with Hysteresis Regulates Either Positive or Negative Output Voltages Shut Down Current: 50 µA Maximum Wide Temperature Range Commercial Commercial Grade : 0 to 70°C (3255) 3255 V C FB Test SS VSW PGND AGND VCC 4 5 3.72K 0.01µF SS 3.3V 1.28k 22µF 22µH MBRS120T3 VOUT 22µF FC3255 1.5A PWM Switching Regulators
MARKING INFORMATION & PIN CONFIGURATIONS (TOP VIEW) SOP-8 2 3 4 8 7 6 5 VC FB SS Test AGND VCC PGND VSW Ordering Number Package Shipping 3255S8T 3255S8R SOP - 8 SOP - 8
100 Units / Tube
2,500 Units / Tape & Reel PIN DESCRIPTION PIN NUMBER PIN SYMBOL FUNCTION VC FB Test SS VCC AGND PGND VSW Loop compensation pin. The V pin is the output of the error amplifier and is used forC loop compensation, current limit and start. Loop compensation can be implemented by a simple RC network as shown in the application diagram on page 2 as R1 and C1. Positive regulator feedback pin. This pin senses a positive output voltage and is referenced to 1.276V. When the voltage at this pin falls below 0.4 V, chip switching frequency reduces to 20% of the nominal frequency. These pins are connected to internal test logic and should either be left floating or tied to ground. Connection to a voltage between 9.5V and 15V shuts down the internal oscillator and leaves the power switch running. Synchronization and shutdown pin. This pin may be used to synchronize the part to nearly twice the base frequency. A TTL low shut the part down and put it into low current mode. If synchronization is not used, this pin should be either tied high or left floating for normal operation. Input power supply pin. This pin supplies power to the part and should have a bypass capacitor connected to AGND. Analog ground. This pin provides a clean ground for the controller circuitry ans should not be in the path of large currents. The output voltage sensing resistors should be connected to the IC substrate. Power ground. This pin is the ground connection for the emitter of the power switching transistor. Connection to a good ground plane is essential. High current switch pin. This pin connects internally to the collector of the power switch. The open voltage across the power switch can be as high as 40V. To minimize radiation, use a trace as short as practical. ABSOLUTE MAXIMUM RATINGS PARAMETER VALUE UNITS Package Thermal Resistance Junction-to-Case, RqJC junction-to-Ambient, RqJC Junction Temperature Range, TJ Storage Temperature Range, TSTG ESD, Human Body Model 165 -40 to +150 -65 to +150 230 1.2 °C / W °C / W kV Lead Temperature (Peak) (reflow - soldering 60 maximum above 183°C) sec. * For detail Ordering Number identification, please see last page. * The maximum package power dissipation must be observed. FC3255 1.5A PWM Switching Regulators
2.0V Regulator Thermal Shutdown Sync Oscillator Frequency Shift 5 :1 PWM LatchS Q Driver
0.4 V Detector
1.276 V Positive Error Amp Slope Compensation PWM Comparator + - VC Switch 63mW Ramp Summer X 5 R MAXIMUM RATINGS: PIN NAME IC Power Input Shutdown / Sync Loop Compensation Voltage Feedback Input Test Pin Power Ground Analog Ground Switch Input PIN SYMBOL VCC SS VC FB Test PGND AGND VSW VMAX 30 V 30 V 6 V 10 V 6 V 0.3 V 0 V 40 V V MIN -0.3 V -0.3 V -0.3 V -0.3 V -0.3 V -0.3 V 0 V -0.3 V ISOURCE N / A 1 mA 10 mA 1 mA 1 mA 4 A N / A 10 mA ISINK 200 mA 1 mA 10 mA 1 mA 1.0 mA 10 mA 10 mA 3 A Test 4µA FC3255 1.5A PWM Switching Regulators
ELECTRICAL CHARACTERISTICS
(2.7 V < V < 30 V; Industrial Grade: 0°C < T < 70°C; Commercial Grade: 0°C < T < 125°C; unless otherwise noted) CC J J CHARACTERISTICS TEST CONDITIONS MIN TYP MAX UNIT FB Reference Voltage FB Input Current FB Reference Voltage Line Regulation Error Amp Transconductance Error Amp Gain Error Amp GainNegative V Source CurrentC V Sink CurrentC V High Clamp Voltage C V Low Clamp Voltage C Base Operating Frequency Reduced Operating Frequency Maximum Duty Cycle FB Frequency Shift Threshold Sync Range Sync Pulse Transition Threshold SS Bias Current Shutdown Threshold Shutdown Delay Error Amplifier Section Oscillator Section Sync/ Shutdown Section Sync Range Shutdown Threshold V tied to FB; measure at FBC FB = VREF V = FBC I = ±25 µA VC (Note 2) (Note 2) FB = 1.0V, V =1.25VC FB = 1.5V, V = 1.25VC FB = 1.0V; V sources 25µAC FB = 1.5V, V sinks 25µAC Reduce V from 1.5V until switchingC stops FB = 1.0V FB = 0V Frequency drops to reduced operating frequency Rise time = 20ns SS = 0V SS = 3.0V
2.7 V V 12VCC
12 V < V 30V CC
1.246 -1.0 300 200 100 200 1.5 0.25 0.75 230 0.36 320 2.5 -15 0.5 1.276 0.1 0.01 550 500 180 625 1.7 0.50 1.05 280 0.40 -3.0 3.0 0.85 V µA % / V µMho V / V V / V µA µA V V V kHz kHz V kHz V µA µs 1.300 1.0 0.03 800 320 1500 1.9 0.65 1.30 310 120 0.44 500 8.0 350 200 1.2 V Threshold C (Note 1) The maximum package power dissipation must be observed. (Note 2) Guaranteed by design, not 100% tested in production. µs Power Management FC3255 1.5A PWM Switching Regulators
(2.7 V < V < 30 V; Industrial Grade: 0°C < T < 70°C; Commercial Grade: 0°C < T < 125°C; unless otherwise noted) CC J J TEST CONDITIONS MIN TYP MAX UNIT CHARACTERISTICS TEST CONDITIONS MIN Power Switch Section Switch Saturation Voltage Switch Current Limit Minimum Pulse Width Switch Leakage General Section Operating Current Shutdown Mode Current Minimum Operation Input Voltage Thermal Shutdown Thermal Hysteresis D I / DVCC SW I = 1.5A, (Note 2)SWITCH I = 1.0A, 0°C T 85°CSWITCH J I =1.0A, -40°C T 0°C(Note 2) SWITCH A I = 10mASWITCH 50% duty cycle(Note 2) 80% duty cycle(Note 2) FB = 0 V, I =4.0A(Note 2 )SW 2.7 V V 12V, 10mA I 1.0ACC SW 12V V 30V, 10mA I 1.0A CC SW 2.7 V V 12V, 10mA I 1.5A CC SW (Note 2) 12V V 30V, 10mA I 1.5A CC SW (Note 2) V = 40 V, V = 0V SW CC I= 0 SW V < 0.8V, SS = 0V, 2.7V V 12V CC C V < 0.8V, SS = 0V, 12V V 30V CC C V switching, maximum I = 10mA SW SW (Note2) (Note2) 1.6 1.5 200 150 0.8 0.55 0.75 0.09 1.9 1.7 250 2.0 5.5 2.45 180 1.4 1.00 1.30 0.45 2.4 2.2 300 100 100 100 8.0 100 2.70 210 V A ns mA / A µA mA µA V (Note 2) Guaranteed by design, not 100% tested in production. FC3255 1.5A PWM Switching Regulators
transistor current is reduced from its nominal value. cess energy before the switch turns back on. counts for the initial current swing. this phase is clamped by the internal current limit. creased once an overvoltage condition is detected. the Bode plot shown in Figure 9. achieving DC accuracy over ling and load variations. Figure 9. A Typical Compensation Network
well up to a full 1.5A switch current. put filter's ESR zero or at half the switching frequency. Figure 10. Bode Plot of the Compensation
proper operation of the error amplifier. function can be added to 3255 of components. rent from rising at a high slope. creases with the size of C3. and determine its expected junction temperature. once the junction temperature exceeds 180°C ± 30°C. tures will ensure a reduced operating life. Figure 15. Soft Start
D = the duty cycle or percentage of switch on-time. sistive properties of the package molding compound. and can usually be ignored for values of R2 up to 7k. The suggested value for R2 is 6.19k.
- In boost circuits, high AC current circulates within
traces and leads should be kept as short as possible.
- Separate the low current signal grounds from the
plane construction for the best results.
- Locate the voltage feedback as near the IC as, pos-
sible to keep the sensitive feedback wiring short. Figure 16. Output Resistor Divider
Figure 18. Additional Application Diagram, 5.0V to -12V/ 75mA
3.3 VIN
Figure 17. Additional Application Diagram, 3.3 V Input, 5.0 V/ 400mA Figure 19. Additional Application Diagram, 2.7 to 13 V Input, ±12 V/ 200 mA Output
Figure 20. Additional Application Diagram, -9.0 V to -28 V Input, Figure 22. Additional Application Diagram, 4.0 V Input, 100 V/ 10 mA Output Boost
50 V 50 V 50 V
50 V50 V50 V
Figure 21. Additional Application Diagram, 2.7 V to 28 V Input, 5.0 V Output
0.275 7.0 0.155 4.0 0.060 1.52 0.050 1.270 0.024 0.6 Inches mm( ) Pad Layout SOP-8 P ACKAGE OUTLINE DIMENSIONS 0.236 ± 0.008
0.050 NOM
1.270 NOM
+0.21 -0.205.990 3.91 ± 0.1 +0.003 -0.0040.154 PIN INDENT 1.600 ± 0.130 0.063 ± 0.005
0.057 NOM
1.450 NOM
0.175 ± 0.075 0.007 ± 0.003 +0.004 -0.0030.016 +0.10 -0.080.410 +0.0018 -0.00050.008 +0.05 -0.010.200 +0.013 -0.0220.028 +0.33 -0.560.710 +0.002 -0.0040.191 +0.05 -0.104.850 Inches mm( ) 0 ~ 8°° FC3255 1.5A PWM Switching Regulators