Datasheet LT1950 (Analog Devices) - 3

LT1950
ELECTRICAL CHARACTERISTICS The
●
denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25
°
C. COMP = open, FB = 1.4V, ROSC = 249k, SYNC = 0V, SLOPE = open, VREF = 0.1
µ
F, SHDN = VIN, BLANK = 0V, ISENSE = 0V, VIN2 = 15V, GATE = 1nF, BOOST = open, VIN = 15V, VSEC = 0V, unless otherwise specified. PARAMETER CONDITIONS MIN TYP MAX UNITS Error Amplifier
FB Reference Voltage 3V < VIN < 25V, VOL + 0.2V < COMP < VOH – 0.2 ● 1.205 1.230 1.254 V FB Input Bias Current FB = FB Reference Voltage –75 –200 nA Open Loop Voltage Gain VOL + 0.2V < COMP < VOH – 0.2 65 85 dB Unity Gain Bandwidth (Note 6) 3 MHz COMP Source Current FB = 1V, COMP = 1.6V ● –0.3 –1.1 –1.8 mA COMP Sink Current FB = 1.4V, COMP = 1.6V 8 13 mA COMP High Level: VOH FB = 1V, ICOMP = – 250µA 2.5 V COMP Active Threshold Start of GATE Switching (Duty Cycle > 0%) 1.0 V COMP Low Level: VOL FB = 1.4V, ICOMP = 250µA 0.15 V
Current Sense
ISENSE Maximum Threshold Duty Cycle < 10%, COMP = VOH 90 100 110 mV ISENSE Input Bias Current COMP = 2.5V, ISENSE = ISENSE Max Threshold –125 –170 –250 µA Default Blanking Time FB = 1V, COMP = 2V, ISENSE = 75mV 110 ns Adjustable Blanking Time FB = 1V, COMP = 2V, ISENSE = 75mV 290 ns BLANK = 75k to Ground Blanking Override Voltage– BLANK = Open, COMP = 2.5V (Note 4) 15 25 40 mV ISENSE Maximum Threshold Turn-Off Delay to Gate COMP = 2V 60 ns Slope Compensation (Note 4) ISENSE Max Threshold (DC < 10%) – (DC = 80%) (Note 4) Default, RSLOPE = ∞ 14 mV 2x Default, RSLOPE = 8k 28 mV 3x Default, RSLOPE = 3.3k 42 mV
Internal Switcher
Boost Switch ILIMIT VIN2 = 8V, 3V < VIN < 10V 70 125 180 mA Boost Switch Off Time VIN2 = 8V, 3V < VIN < 10V 250 500 1000 ns VIN2: Boost Disable 3V < VIN < 10V ● 9.5 11.0 11.75 V VIN2: Boost Disable Hysteresis 3V < VIN < 10V –1.0 V VIN2: Gate Enable 3V < VIN < 10V, FB = 1V (Note 4) ● 7.0 8.2 9.27 V VIN2: Gate Enable Hysteresis 3V < VIN < 10V, FB = 1V (Note 4) –0.6 V
GATE Driver Output
GATE Rise Time FB = 1V, VIN2 = 12V, CL = 1nF (Notes 3, 6) 50 ns GATE Fall Time FB = 1V, VIN2 = 12V, CL = 1nF (Notes 3, 6) 30 ns GATE Clamp Voltage IGATE = 0µA, COMP = 2.5V, FB = 6V 11.5 13 14.5 V GATE Low Level IGATE = 20mA 0.25 0.4 V IGATE = 200mA 1.2 1.75 V GATE High Level IGATE = –20mA, VIN2 = 12V, COMP = 2.5V, FB = 6V 10 V IGATE = –200mA, VIN2 = 12V, COMP = 2.5V, FB = 6V 9.75 V Maximum Duty Cycle FB = 1V, fOSC = 200kHz 90 95 97 % 1950fa 3