Datasheet LT3797 (Analog Devices) - 8
| Manufacturer | Analog Devices |
| Description | Triple Output LED Driver Controller |
| Pages / Page | 36 / 8 — TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C unless otherwise noted. Top … |
| Revision | C |
| File Format / Size | PDF / 381 Kb |
| Document Language | English |
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C unless otherwise noted. Top Gate (PMOS) Rise/Fall Time
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LT3797
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C unless otherwise noted. Top Gate (PMOS) Rise/Fall Time INTVCC vs Temperature, VIN INTVCC Current Limit vs VIN, fSW vs Capacitance
7.550 250 1200 L = 47µH 225 800kHz 700kHz >900kHz (mA) 1000 200 7.525 175 600kHz 800 VIN = 2.5V V 500kHz IN = 24V INTVCC_LMT 150 FALL TIME (V) 400kHz CC 7.500 125 600 INTV 300kHz TIME (ns) V 100 IN = 40V 400 75 7.475 200kHz CURRENT LIMIT I 50 CC 200 RISE TIME INTV 25 100kHz 7.450 0 0 –50 –25 0 25 50 75 100 125 0 3 6 9 12 15 18 21 24 27 30 33 36 39 0 1 2 3 4 5 6 7 8 9 10 TEMPERATURE (°C) V CAPACITANCE (nF) IN (V) 3797 G19 3739 G20 3797 G21
PIN FUNCTIONS FLT1, FLT2, FLT3 (Pins 1, 2, 3):
Open-Collector Pull-
CTRL1, CTRL2, CTRL3 (Pins 8, 9, 10):
Current Sense Downs on FLT Pins Report The Fault Conditions: Threshold Adjustment Pins. Sets voltage across external 1. VIN > 41V (typical) sense resistor between ISP and ISN pins of the respective 2. Overtemperature (TJ > 165°C) converter: 3. INTVCC < 5.2V (typical) VISP-ISN = 0V, when VCTRL < 0.2V 4. OVLO > 1.25V (typical) VISP-ISN = (VCTRL – 0.2V)/4, when 0.2V < VCTRL < 1.2V 5. LED Overcurrent V 6. Open LED ISP-ISN = 250mV, when VCTRL >1.2V 7. Output Overvoltage Connect CTRL pins to VREF for the 250mV default thresh- old. When V
PWM1, PWM2, PWM3 (Pins 4, 5, 6):
Pulse Width CTRL < 150mV (typical), the respective con- verter goes into idle mode, which is the same as PWM pin Modulated Input Pins. Signal low causes the respec- being pulled low. Do not leave these pins open. tive converter to go into idle mode which means it stops switching, the TG pin transitions high, the quiescent cur-
RT (Pin 11):
Switching Frequency Adjustment Pin. Set rents are reduced, and the VC becomes high impedance. the frequency using a resistor to GND. Do not leave the If not used, connect to the REF pin. RT pin open.
V SYNC (Pin 12):
The SYNC pin is used to synchronize the
REF (Pin 7):
Reference Output Pin. Can supply up to 450µA. This pin drives a resistor divider for the CTRL1, internal oscillator to an external logic-level signal. The RT CTRL2, CTRL3 pins, either for analog dimming or for tem- resistor should be chosen to program an internal switch- perature limit/compensation of LED loads. The normal ing frequency 20% slower than the SYNC pulse frequency. output voltage is 2V. Gate turn-on occurs at a 0.2µs (typical) delay after the rising edge of SYNC. Tie SYNC to GND if not used. Rev C 8 For more information www.analog.com Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Revision History Typical Application Related Parts Features Applications Typical Application Description 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 Typical Application Related Parts
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C unless otherwise noted. Top Gate (PMOS) Rise/Fall Time INTVCC vs Temperature, VIN INTVCC Current Limit vs VIN, fSW vs Capacitance
7.550 250 1200 L = 47µH 225 800kHz 700kHz >900kHz (mA) 1000 200 7.525 175 600kHz 800 VIN = 2.5V V 500kHz IN = 24V INTVCC_LMT 150 FALL TIME (V) 400kHz CC 7.500 125 600 INTV 300kHz TIME (ns) V 100 IN = 40V 400 75 7.475 200kHz CURRENT LIMIT I 50 CC 200 RISE TIME INTV 25 100kHz 7.450 0 0 –50 –25 0 25 50 75 100 125 0 3 6 9 12 15 18 21 24 27 30 33 36 39 0 1 2 3 4 5 6 7 8 9 10 TEMPERATURE (°C) V CAPACITANCE (nF) IN (V) 3797 G19 3739 G20 3797 G21
PIN FUNCTIONS FLT1, FLT2, FLT3 (Pins 1, 2, 3):
Open-Collector Pull-
CTRL1, CTRL2, CTRL3 (Pins 8, 9, 10):
Current Sense Downs on FLT Pins Report The Fault Conditions: Threshold Adjustment Pins. Sets voltage across external 1. VIN > 41V (typical) sense resistor between ISP and ISN pins of the respective 2. Overtemperature (TJ > 165°C) converter: 3. INTVCC < 5.2V (typical) VISP-ISN = 0V, when VCTRL < 0.2V 4. OVLO > 1.25V (typical) VISP-ISN = (VCTRL – 0.2V)/4, when 0.2V < VCTRL < 1.2V 5. LED Overcurrent V 6. Open LED ISP-ISN = 250mV, when VCTRL >1.2V 7. Output Overvoltage Connect CTRL pins to VREF for the 250mV default thresh- old. When V
PWM1, PWM2, PWM3 (Pins 4, 5, 6):
Pulse Width CTRL < 150mV (typical), the respective con- verter goes into idle mode, which is the same as PWM pin Modulated Input Pins. Signal low causes the respec- being pulled low. Do not leave these pins open. tive converter to go into idle mode which means it stops switching, the TG pin transitions high, the quiescent cur-
RT (Pin 11):
Switching Frequency Adjustment Pin. Set rents are reduced, and the VC becomes high impedance. the frequency using a resistor to GND. Do not leave the If not used, connect to the REF pin. RT pin open.
V SYNC (Pin 12):
The SYNC pin is used to synchronize the
REF (Pin 7):
Reference Output Pin. Can supply up to 450µA. This pin drives a resistor divider for the CTRL1, internal oscillator to an external logic-level signal. The RT CTRL2, CTRL3 pins, either for analog dimming or for tem- resistor should be chosen to program an internal switch- perature limit/compensation of LED loads. The normal ing frequency 20% slower than the SYNC pulse frequency. output voltage is 2V. Gate turn-on occurs at a 0.2µs (typical) delay after the rising edge of SYNC. Tie SYNC to GND if not used. Rev C 8 For more information www.analog.com Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Revision History Typical Application Related Parts Features Applications Typical Application Description 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 Typical Application Related Parts
