Datasheet LT3781 (Analog Devices) - 3
| Fabricante | Analog Devices |
| Descripción | Bootstrap Start Dual Transistor Synchronous Forward Controller |
| Páginas / Página | 20 / 3 — ELECTRICAL CHARACTERISTICS The |
| Formato / tamaño de archivo | PDF / 260 Kb |
| Idioma del documento | Inglés |
ELECTRICAL CHARACTERISTICS The
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LT3781
ELECTRICAL CHARACTERISTICS The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25
°
C. VCC = VBST = 12V, VBSTREF = 0V, VVC = 2V, VTS = 0V, VFB = VREF = 1.25V, CTG = CBG = CSG = 1000pF. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Error Amp
VFB Error Amplifier Reference Voltage Measured at Feedback Pin 1.242 1.250 1.258 V ● 1.225 1.265 V IFB Feedback Input Current VFB = VREF –50 nA AV Error Amplifier Voltage Gain 72 dB IVC Error Amplifier Current Limit Source ● 10 25 mA Sink ● 0.5 1 mA VVC Zero Current Output Voltage 1.4 V Maximum Output Voltage 3.2 V GBW Gain Bandwidth Product (Note 3) 1 MHz
Current Sense
AV Amplifier DC Gain 12 V/V ISENSE Input Bias Current – 275 µA VSENSE Current Limit Threshold Measured at SENSE Pin 135 150 165 mV ● 130 170 mV tD Current Sense to Switch Delay 175 ns tMIN Switch Minimum On Time Measured at BG Output 250 ns
THERM and OVLO Fault Detectors
VTHERM/ Threshold (Rising Edge) ● 1.2 1.25 1.3 V VOVLO Threshold Hysteresis ● 20 40 60 mV tD Fault Delay to Output Disable >50mV Overdrive 650 ns
Oscillator and Synchronization Decoder
fOSC Oscillator Frequency, Free Run Measured at FSET Pin 700 kHz Frequency Programming Error fOSC ≤ 500kHz (Note 3) ● –10 5 % IFSET FSET Input Bias Current FSET Charging, VFSET = 2V 50 nA VSYNC SYNC Logic High Input Threshold Positive-Going Edge ● 1.4 2 V SYNC Logic Low Input Threshold Negative-Going Edge ● 0.8 1.4 V fSYNC SYNC Frequency ● fOSC/2 350 kHz tH, L Maximum SYNC Pulse Width fOSC = Oscillator Free-Run Frequency 1/fOSC s (Logic High or Logic Low)
Output Drivers
VTG TG On Voltage ● 11 11.5 V TG Off Voltage ● 0.1 0.5 V tTGr/f TG Rise/Fall Time 10% to 90%/90% to 10% 35 ns VBG BG On Voltage ● 11 11.5 12 V BG Off Voltage ● 0.1 0.5 V tBGr/f BG Rise/Fall Time 10% to 90%/90% to 10% 35 ns VSG SG On Voltage ● 11 11.5 12 V SG Off Voltage ● 0.1 0.5 V tSGr/f SG Rise/Fall Time 10% to 90%/90% to 10% 35 ns tSG-BG SG to BG Enable Lag Time 4V On/Off Thresholds ● 80 150 300 ns tTG-BG TG to BG Enable Lag Time 4V On/Off Thresholds 100 ns 3781f 3
ELECTRICAL CHARACTERISTICS The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25
°
C. VCC = VBST = 12V, VBSTREF = 0V, VVC = 2V, VTS = 0V, VFB = VREF = 1.25V, CTG = CBG = CSG = 1000pF. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Error Amp
VFB Error Amplifier Reference Voltage Measured at Feedback Pin 1.242 1.250 1.258 V ● 1.225 1.265 V IFB Feedback Input Current VFB = VREF –50 nA AV Error Amplifier Voltage Gain 72 dB IVC Error Amplifier Current Limit Source ● 10 25 mA Sink ● 0.5 1 mA VVC Zero Current Output Voltage 1.4 V Maximum Output Voltage 3.2 V GBW Gain Bandwidth Product (Note 3) 1 MHz
Current Sense
AV Amplifier DC Gain 12 V/V ISENSE Input Bias Current – 275 µA VSENSE Current Limit Threshold Measured at SENSE Pin 135 150 165 mV ● 130 170 mV tD Current Sense to Switch Delay 175 ns tMIN Switch Minimum On Time Measured at BG Output 250 ns
THERM and OVLO Fault Detectors
VTHERM/ Threshold (Rising Edge) ● 1.2 1.25 1.3 V VOVLO Threshold Hysteresis ● 20 40 60 mV tD Fault Delay to Output Disable >50mV Overdrive 650 ns
Oscillator and Synchronization Decoder
fOSC Oscillator Frequency, Free Run Measured at FSET Pin 700 kHz Frequency Programming Error fOSC ≤ 500kHz (Note 3) ● –10 5 % IFSET FSET Input Bias Current FSET Charging, VFSET = 2V 50 nA VSYNC SYNC Logic High Input Threshold Positive-Going Edge ● 1.4 2 V SYNC Logic Low Input Threshold Negative-Going Edge ● 0.8 1.4 V fSYNC SYNC Frequency ● fOSC/2 350 kHz tH, L Maximum SYNC Pulse Width fOSC = Oscillator Free-Run Frequency 1/fOSC s (Logic High or Logic Low)
Output Drivers
VTG TG On Voltage ● 11 11.5 V TG Off Voltage ● 0.1 0.5 V tTGr/f TG Rise/Fall Time 10% to 90%/90% to 10% 35 ns VBG BG On Voltage ● 11 11.5 12 V BG Off Voltage ● 0.1 0.5 V tBGr/f BG Rise/Fall Time 10% to 90%/90% to 10% 35 ns VSG SG On Voltage ● 11 11.5 12 V SG Off Voltage ● 0.1 0.5 V tSGr/f SG Rise/Fall Time 10% to 90%/90% to 10% 35 ns tSG-BG SG to BG Enable Lag Time 4V On/Off Thresholds ● 80 150 300 ns tTG-BG TG to BG Enable Lag Time 4V On/Off Thresholds 100 ns 3781f 3