Datasheet LT1725 (Analog Devices) - 3
| Manufacturer | Analog Devices |
| Description | General Purpose Isolated Flyback Controller |
| Pages / Page | 28 / 3 — ELECTRICAL CHARACTERISTICS The |
| File Format / Size | PDF / 265 Kb |
| Document Language | English |
ELECTRICAL CHARACTERISTICS The
Model Line for this Datasheet
Text Version of Document
LT1725
ELECTRICAL CHARACTERISTICS The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25
°
C. VCC = 14V, GATE open, VC = 1.4V unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Gate Output
VGATE Output High Level IGATE = 100mA ● 11.5 12.1 V IGATE = 500mA ● 11.0 11.8 V Output Low Level IGATE = 100mA ● 0.3 0.45 V IGATE = 500mA ● 0.6 1.0 V IGATE Output Sink Current in Shutdown, VUVLO = 0V VGATE = 2V ● 1.2 2.5 mA tr Rise Time CL = 1000pF 30 ns tf Fall Time CL = 1000pF 30 ns
Current Amplifier
VC Control Pin Threshold Duty Cycle = Min 0.90 1.12 1.25 V ● 0.80 1.35 V VISENSE Switch Current Limit Duty Cycle ≤ 30% 220 250 270 mV Duty Cycle ≤ 30% ● 200 280 mV Duty Cycle = 80% 220 mV ∆VISENSE/∆VC 0.30 mV
Timing
f Switching Frequency COSCAP = 100pF 90 100 115 kHz ● 80 125 kHz COSCAP Oscillator Capacitor Value (Note 2) 33 200 pF tON Minimum Switch On Time RtON = 50k 200 ns tED Flyback Enable Delay Time RENDLY = 50k 200 ns tEN Minimum Flyback Enable Time RMENAB = 50k 200 ns Rt Timing Resistor Value (Note 2) 24 200 kΩ Maximum Switch Duty Cycle ● 85 90 %
Load Compensation
Sense Offset Voltage 2 5 mV Current Gain Factor 0.80 0.95 1.05 mV
UVLO Function
VUVLO UVLO Pin Threshold ● 1.21 1.25 1.29 V IUVLO UVLO Pin Bias Current VUVLO = 1.2V – 0.25 + 0.1 + 0.25 µA VUVLO = 1.3V – 4.50 – 3.5 – 2.50 µA
3V Output Function
VREF Reference Output Voltage ILOAD = 1mA ● 2.8 3.0 3.2 V Output Impedance 10 Ω Current Limit ● 8 15 mA
Note 1:
Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
Note 2:
Component value range guaranteed by design.
Note 3:
The VCC turn-on/turn-off voltages and hysteresis voltage are proportional in magnitude to each other-guaranteed by design. 1725fa 3
ELECTRICAL CHARACTERISTICS The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25
°
C. VCC = 14V, GATE open, VC = 1.4V unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Gate Output
VGATE Output High Level IGATE = 100mA ● 11.5 12.1 V IGATE = 500mA ● 11.0 11.8 V Output Low Level IGATE = 100mA ● 0.3 0.45 V IGATE = 500mA ● 0.6 1.0 V IGATE Output Sink Current in Shutdown, VUVLO = 0V VGATE = 2V ● 1.2 2.5 mA tr Rise Time CL = 1000pF 30 ns tf Fall Time CL = 1000pF 30 ns
Current Amplifier
VC Control Pin Threshold Duty Cycle = Min 0.90 1.12 1.25 V ● 0.80 1.35 V VISENSE Switch Current Limit Duty Cycle ≤ 30% 220 250 270 mV Duty Cycle ≤ 30% ● 200 280 mV Duty Cycle = 80% 220 mV ∆VISENSE/∆VC 0.30 mV
Timing
f Switching Frequency COSCAP = 100pF 90 100 115 kHz ● 80 125 kHz COSCAP Oscillator Capacitor Value (Note 2) 33 200 pF tON Minimum Switch On Time RtON = 50k 200 ns tED Flyback Enable Delay Time RENDLY = 50k 200 ns tEN Minimum Flyback Enable Time RMENAB = 50k 200 ns Rt Timing Resistor Value (Note 2) 24 200 kΩ Maximum Switch Duty Cycle ● 85 90 %
Load Compensation
Sense Offset Voltage 2 5 mV Current Gain Factor 0.80 0.95 1.05 mV
UVLO Function
VUVLO UVLO Pin Threshold ● 1.21 1.25 1.29 V IUVLO UVLO Pin Bias Current VUVLO = 1.2V – 0.25 + 0.1 + 0.25 µA VUVLO = 1.3V – 4.50 – 3.5 – 2.50 µA
3V Output Function
VREF Reference Output Voltage ILOAD = 1mA ● 2.8 3.0 3.2 V Output Impedance 10 Ω Current Limit ● 8 15 mA
Note 1:
Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
Note 2:
Component value range guaranteed by design.
Note 3:
The VCC turn-on/turn-off voltages and hysteresis voltage are proportional in magnitude to each other-guaranteed by design. 1725fa 3
