Datasheet LT3745-1 (Analog Devices) - 3

LT3745-1
ELECTRICAL CHARACTERISTICS The
l
denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 12V, VCC = 3.3V, VEN/UVLO = 1.5V, VFB = 1.5V, VISP = VISN = 0V, RT = 105k, RISET = 60.4k, CCAP = 0.47µF to VIN, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Undervoltage Lockout (UVLO)
VCC UVLO Threshold VCC Rising 2.76 2.86 2.96 V VCC Falling 2.58 2.68 2.78 V EN/UVLO Shutdown Threshold IVCC <1mA 0.35 V UVLO Threshold VEN/UVLO Rising 1.26 1.30 1.34 V VEN/UVLO Falling 1.18 1.22 1.26 V IEN/UVLO EN/UVLO Bias Current VEN/UVLO = VCC = 3.3V 0.1 1 µA (VIN – VCAP) UVLO Threshold (VIN – VCAP) Rising 4.6 4.9 5.2 V (VIN – VCAP) Falling 4.2 4.5 4.8 V
Soft-Start (SS)
ISS Soft-Start Charge Current VSS = 1V –16 –12 –8 µA Soft-Start Discharge Current VSS = VCC, VEN/UVLO = 1V 330 µA VSS(TH) Soft-Start Reset Threshold 0.35 V
Oscillator
VRT RT Pin Voltage 1.186 1.205 1.224 V IRT RT Pin Current Limit VRT = 0V –80 µA fOSC Oscillator Frequency RT = 280k 184 204 224 kHz RT = 105k 460 510 560 kHz RT = 46.4k 935 1035 1135 kHz fSYNC Sync Frequency Range (Note 5) RT = 348k 200 1000 kHz SYNC LOGIC VCC = 3V to 3.6V High Level Voltage 2.4 VCC V Low Level Voltage 0 0.6 V
Error Amplifiers and Loop Dynamics
VFB FB Regulation Voltage VISN = 5V l 1.186 1.210 1.234 V IFB FB Input Bias Current VISN = 5V, VFB Regulated –120 nA LED Regulation Voltage VISN = 5V, VFB = 1V 0.6 0.7 0.8 V tOFF(MIN) Minimum GATE Off-Time VISP = VISN = 5V, VFB = 1V 120 ns tON(MIN) Minimum GATE On-Time (VISP – VISN) = 60mV, VISN = 5V, VFB = 1V 200 ns
Current Sense Amplifier
ISP/ISN Pin Common Mode VISP = VISN l 0 36 V VIN to ISN Dropout Voltage (VIN – VISN) VISP = VISN, VFB = 1V l 1.7 2.1 V Current Limit Sense Threshold (VISP – VISN) VFB = 1V 30 44 58 mV IISP ISP Input Bias Current –24 µA IISN ISN Input Bias Current –48 µA
Gate Driver
VBIAS CAP Bias Voltage (VIN – VCAP) 7V < VIN < 55V 6.4 6.8 7.1 V ICAP CAP Bias Current Limit (VIN – VCAP) = VBIAS – 0.5V 22 mA GATE High Level (VIN – VGATE) IGATE = –100mA 0.4 V GATE Low Level (VGATE – VCAP) IGATE = 100mA 0.3 V GATE Rise Time CGATE = 3.3nF to VIN 30 ns GATE Fall Time CGATE = 3.3nF to VIN 30 ns 37451f 3 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Timing Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Application Package Description Typical Application Related Parts