Datasheet LT3825 (Analog Devices) - 3
| Manufacturer | Analog Devices |
| Description | Isolated No-Opto Synchronous Flyback Controller with Wide Input Supply Range |
| Pages / Page | 32 / 3 — ELECTRICAL. CHARACTERISTICS The. denotes the specifications which apply … |
| File Format / Size | PDF / 390 Kb |
| Document Language | English |
ELECTRICAL. CHARACTERISTICS The. denotes the specifications which apply over the full operating
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LT3825
ELECTRICAL CHARACTERISTICS The
l
denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at T – A = 25°C. VCC = 14V; PG, SG Open; VC = 1.5V, VSENSE = 0V; RCMP = 1k, RtON = 90k, RPGDLY = 27.4k, RENDLY = 90k, unless otherwise specified (Note 3). PARAMETER CONDITIONS MIN TYP MAX UNITS
Reference Voltage Line Regulation 12V ≤ VCC ≤ 18V l 0.005 0.02 %/V Feedback Amplifier Voltage Gain VC = 1.2V to 1.7V 1400 V/V Soft-Start Charging Current VSFST = 1.5V 16 20 25 µA Soft-Start Discharge Current VSFST = 1.5V, VUVLO = 0V 0.8 1.3 mA Control Pin Threshold (VC) Duty Cycle = Min 1.0 V
Gate Outputs
PG, SG Output High Level l 6.6 7.4 8.0 V PG, SG Output Low Level l 0.01 0.05 V PG, SG Output Shutdown Strength VUVLO = 0V; IPG, ISG = 20mA l 1.6 2.3 V PG Rise Time CPG = 1nF 11 ns SG Rise Time CSG = 1nF 15 ns PG, SG Fall Time CPG, CSG = 1nF 10 ns
Current Amplifier
Switch Current Limit at Maximum V + C VSENSE l 88 98 110 mV ∆VSENSE/∆VC 0.07 V/V Sense Voltage Overcurrent Fault Voltage V + SENSE l 206 230 mV
Timing
Switching Frequency (fOSC) COSC = 100pF l 84 100 110 kHz Oscillator Capacitor Value (COSC) (Note 6) 33 200 pF Minimum Switch On-Time (tON(MIN)) 200 ns Flyback Enable Delay Time (tED) 265 ns PG Turn-On Delay Time (tPGDLY) 200 ns Maximum Switch Duty Cycle l 85 88 % SYNC Pin Threshold l 1.53 2.1 V SYNC Pin Input Resistance 40 kΩ
Load Compensation
Load Comp to V + SENSE Offset Voltage VRCMP with VSENSE = 0V 1 mV Feedback Pin Load Compensation Current V + SENSE = 20mV, VFB = 1.230V 20 µA
UVLO Function
UVLO Pin Threshold (VUVLO) l 1.215 1.240 1.265 V UVLO Pin Bias Current VUVLO = 1.2V –0.25 0 ±0.25 µA VUVLO = 1.3V –4.50 –3.4 –2.50 µA
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings range are assured by design, characterization and correlation with statistical may cause permanent damage to the device. Exposure to any Absolute process controls. Note that the maximum ambient temperature consistent Maximum Rating condition for extended periods may affect device with these specifications is determined by specific operating conditions in reliability and lifetime. conjunction with board layout, the rated package thermal resistance and other
Note 2:
This IC includes overtemperature protection that is intended environmental factors. to protect the device during momentary overload conditions. Junction
Note 4:
TJ is calculated from the ambient temperature TA and power temperature will exceed 125°C when overtemperature protection is active. dissipation PD according to the following formula: Continuous operation above the specified maximum operating junction TJ = TA + (PD • 40°C/W) temperature may impair device reliability.
Note 5:
Supply current does not include gate charge current to the
Note 3:
The LT3825 is tested under pulsed load conditions, such that TJ ≈ TA. MOSFETs. See Applications Information. The LT3825E is guaranteed to meet performance specifications from 0°C to
Note 6:
Component value range guaranteed by design. 125°C. Specifications over the –40°C to 125°C operating junction temperature 3825fe 3 Document Outline Features Description Applications Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Revision History Related Parts
ELECTRICAL CHARACTERISTICS The
l
denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at T – A = 25°C. VCC = 14V; PG, SG Open; VC = 1.5V, VSENSE = 0V; RCMP = 1k, RtON = 90k, RPGDLY = 27.4k, RENDLY = 90k, unless otherwise specified (Note 3). PARAMETER CONDITIONS MIN TYP MAX UNITS
Reference Voltage Line Regulation 12V ≤ VCC ≤ 18V l 0.005 0.02 %/V Feedback Amplifier Voltage Gain VC = 1.2V to 1.7V 1400 V/V Soft-Start Charging Current VSFST = 1.5V 16 20 25 µA Soft-Start Discharge Current VSFST = 1.5V, VUVLO = 0V 0.8 1.3 mA Control Pin Threshold (VC) Duty Cycle = Min 1.0 V
Gate Outputs
PG, SG Output High Level l 6.6 7.4 8.0 V PG, SG Output Low Level l 0.01 0.05 V PG, SG Output Shutdown Strength VUVLO = 0V; IPG, ISG = 20mA l 1.6 2.3 V PG Rise Time CPG = 1nF 11 ns SG Rise Time CSG = 1nF 15 ns PG, SG Fall Time CPG, CSG = 1nF 10 ns
Current Amplifier
Switch Current Limit at Maximum V + C VSENSE l 88 98 110 mV ∆VSENSE/∆VC 0.07 V/V Sense Voltage Overcurrent Fault Voltage V + SENSE l 206 230 mV
Timing
Switching Frequency (fOSC) COSC = 100pF l 84 100 110 kHz Oscillator Capacitor Value (COSC) (Note 6) 33 200 pF Minimum Switch On-Time (tON(MIN)) 200 ns Flyback Enable Delay Time (tED) 265 ns PG Turn-On Delay Time (tPGDLY) 200 ns Maximum Switch Duty Cycle l 85 88 % SYNC Pin Threshold l 1.53 2.1 V SYNC Pin Input Resistance 40 kΩ
Load Compensation
Load Comp to V + SENSE Offset Voltage VRCMP with VSENSE = 0V 1 mV Feedback Pin Load Compensation Current V + SENSE = 20mV, VFB = 1.230V 20 µA
UVLO Function
UVLO Pin Threshold (VUVLO) l 1.215 1.240 1.265 V UVLO Pin Bias Current VUVLO = 1.2V –0.25 0 ±0.25 µA VUVLO = 1.3V –4.50 –3.4 –2.50 µA
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings range are assured by design, characterization and correlation with statistical may cause permanent damage to the device. Exposure to any Absolute process controls. Note that the maximum ambient temperature consistent Maximum Rating condition for extended periods may affect device with these specifications is determined by specific operating conditions in reliability and lifetime. conjunction with board layout, the rated package thermal resistance and other
Note 2:
This IC includes overtemperature protection that is intended environmental factors. to protect the device during momentary overload conditions. Junction
Note 4:
TJ is calculated from the ambient temperature TA and power temperature will exceed 125°C when overtemperature protection is active. dissipation PD according to the following formula: Continuous operation above the specified maximum operating junction TJ = TA + (PD • 40°C/W) temperature may impair device reliability.
Note 5:
Supply current does not include gate charge current to the
Note 3:
The LT3825 is tested under pulsed load conditions, such that TJ ≈ TA. MOSFETs. See Applications Information. The LT3825E is guaranteed to meet performance specifications from 0°C to
Note 6:
Component value range guaranteed by design. 125°C. Specifications over the –40°C to 125°C operating junction temperature 3825fe 3 Document Outline Features Description Applications Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Revision History Related Parts
