Datasheet LT1070, LT1071 (Linear Technology) - 3

LT1070/LT1071
ELECTRICAL CHARACTERISTICS The
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denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25
°
C. VIN = 15V, VC = 0.5V, VFB = VREF, output pin open unless otherwise specified. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VFB Flyback Reference Voltage IFB = 50µA 15 16.3 17.6 V ● 14 18.0 V Change in Flyback Reference Voltage 0.05 ≤ IFB ≤ 1mA 4.5 6.8 8.5 V Flyback Reference Voltage Line Regulation IFB = 50µA, 3V ≤ VIN ≤ VMAX (Note 3) 0.01 0.03 %/V Flyback Amplifier Transconductance (gm) ∆IC = ±10µA 150 300 650 µmho Flyback Amplifier Source and Sink Current VC = 0.6V, IFB = 50µA (Source) ● 15 32 70 µA VC = 0.6V, IFB = 50µA (Sink) ● 25 40 70 µA BV Output Switch Breakdown Voltage 3V ≤ VIN ≤ VMAX, ISW = 1.5mA (LT1070/LT1071) ● 65 90 V (LT1070HV/LT1071HV) ● 75 90 V VSAT Output Switch “On” Resistance (Note 4) LT1070 ● 0.15 0.24 Ω LT1071 ● 0.30 0.50 Ω Control Voltage to Switch Current LT1070 8 A/V Transconductance LT1071 4 A/V ILIM Switch Current Limit (LT1070) Duty Cycle ≤ 50%, TJ ≥ 25°C ● 5 10 A Duty Cycle ≤ 50%, TJ < 25°C ● 5 11 A Duty Cycle = 80% (Note 5) ● 4 10 A Switch Current Limit (LT1071) Duty Cycle ≤ 50%, TJ ≥ 25°C ● 2.5 5.0 A Duty Cycle ≤ 50%, TJ < 25°C ● 2.5 5.5 A Duty Cycle = 80% (Note 5) ● 2.0 5.0 A ∆IIN Supply Current Increase During 25 35 mA/A ∆ISW Switch “On” Time f Switching Frequency 35 40 45 kHz ● 33 47 kHz DC (Max) Maximum Switch Duty Cycle 90 92 97 % Flyback Sense Delay Time 1.5 µs Shutdown Mode Supply Current 3V ≤ VIN ≤ VMAX, VC = 0.05V 100 250 µA Shutdown Mode Threshold Voltage 3V ≤ VIN ≤ VMAX 100 150 250 mV ● 50 300 mV
Note 1:
Absolute Maximum Ratings are those values beyond which the life of t = Minimum “on” time of LT1070/LT1071 in current limit, ≈1µs a device may be impaired. f = Operating frequency (40kHz)
Note 2:
Minimum switch “on” time for the LT1070/LT1071 in current limit is VF = Forward voltage of external catch diode at ILIMIT ≈1µs. This limits the maximum input voltage during short-circuit conditions, ILIMIT = Current limit of LT1070 (≈8A), LT1071 (≈ 4A) in the buck and inverting modes only, to ≈ 35V. Normal (unshorted) conditions RL = Internal series resistance of inductor are not affected. Mask changes are being implemented which will reduce
Note 3:
VMAX = 55V for LT1070HV and LT1071HV to avoid switch minimum “on” time to ≤ 1µs, increasing maximum short-circuit input voltage breakdown. above 40V. If the present LT1070/LT1071 (contact factory for package date
Note 4:
Measured with VC in hi clamp, VFB = 0.8V. ISW = 4A for LT1070 code) is being operated in the buck or inverting mode at high input voltages and 2A for LT1071. and short-circuit conditions are expected, a resistor must be placed in series
Note 5:
For duty cycles (DC) between 50% and 80%, minimum with the inductor, as follows: guaranteed switch current is given by ILIM = 3.33 (2 – DC) for the The value of the resistor is given by: LT1070 and ILIM = 1.67 (2 – DC) for the LT1071. t • f • V R = IN – VF – RL ILIMIT 10701fe 3