Datasheet LT1681 (Analog Devices) - 3
| Manufacturer | Analog Devices |
| Description | Dual Transistor Synchronous Forward Controller |
| Pages / Page | 20 / 3 — ELECTRICAL CHARACTERISTICS The |
| File Format / Size | PDF / 281 Kb |
| Document Language | English |
ELECTRICAL CHARACTERISTICS The
Model Line for this Datasheet
Text Version of Document
LT1681
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, VFB = VREF = 1.25V, CTG = CBG = CSG = 1000pF. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS 5V External Reference
V5VREF 5V Reference Voltage 0 ≤ (I5VREF – IVC) < 20mA 4.85 5 5.10 V ● 4.80 5.15 V I5VREFSC Short-Circuit Current Source, IVC = 0 ● 20 45 mA R5VREF Output Impedance 0 ≤ (I5VREF – IVC) < 20mA 1 Ω
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 and Blanking
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 VBLKSENS Blanking Input Threshold ● 4.5 5 5.5 V IBLKSENS Blanking Input Bias Current – 2 µA tMIN Switch Minimum On Time VBLKSENS = VBG, Measured at BG Output 250 ns
IMAX Sense
IIMAX Input Bias Current – 250 µA VIMAX IMAX Threshold (Rising Edge) Measured at IMAX Input ● 320 360 400 mV IMAX Threshold Hysteresis Measured at IMAX Input 140 mV tP IMAX Output Switch Disable Delay Measured at BG Output 130 ns
THERM and OVLO Fault Detectors
VTHERM/ Threshold (Rising Edge) ● 1.2 1.25 1.3 V VOVLO Threshold Hysteresis ● 20 40 60 mV tP 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, Free Run 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) 1681f 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, VFB = VREF = 1.25V, CTG = CBG = CSG = 1000pF. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS 5V External Reference
V5VREF 5V Reference Voltage 0 ≤ (I5VREF – IVC) < 20mA 4.85 5 5.10 V ● 4.80 5.15 V I5VREFSC Short-Circuit Current Source, IVC = 0 ● 20 45 mA R5VREF Output Impedance 0 ≤ (I5VREF – IVC) < 20mA 1 Ω
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 and Blanking
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 VBLKSENS Blanking Input Threshold ● 4.5 5 5.5 V IBLKSENS Blanking Input Bias Current – 2 µA tMIN Switch Minimum On Time VBLKSENS = VBG, Measured at BG Output 250 ns
IMAX Sense
IIMAX Input Bias Current – 250 µA VIMAX IMAX Threshold (Rising Edge) Measured at IMAX Input ● 320 360 400 mV IMAX Threshold Hysteresis Measured at IMAX Input 140 mV tP IMAX Output Switch Disable Delay Measured at BG Output 130 ns
THERM and OVLO Fault Detectors
VTHERM/ Threshold (Rising Edge) ● 1.2 1.25 1.3 V VOVLO Threshold Hysteresis ● 20 40 60 mV tP 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, Free Run 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) 1681f 3
