lt3571 Linear Technology Corporation, lt3571 Datasheet
lt3571
Available stocks
Related parts for lt3571
lt3571 Summary of contents
Page 1
... The LT 3571 is a current mode step-up DC/DC converter designed to bias avalanche photodiodes (APDs) in optical receivers with an output voltage up to 75V. The LT3571 features a high side fi xed voltage drop APD current monitor with better than 10% relative accuracy over the entire temperature range. The integrated power switch, Schottky diode and APD current monitor allow a small solution footprint and low solution cost ...
Page 2
... LT3571EUD#PBF LT3571EUD#TRPBF LT3571IUD#PBF LT3571IUD#TRPBF Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi label on the shipping container. For more information on lead free part marking, go to: For more information on tape and reel specifi cations, go to: ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi ...
Page 3
... MONIN APD Note 2: The LT3571E is guaranteed to meet specifi ed performance from 0°C to 125°C junction temperature. Specifi cations over the –40°C to 125°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LT3571I is guaranteed to meet performance specifi ...
Page 4
... LT3571 TYPICAL PERFORMANCE CHARACTERISTICS Switch Current Limit vs Duty Cycle 500 450 400 350 300 250 DUTY CYCLE (%) 3571 G01 Schottky Forward Drop 950 900 850 800 750 700 650 600 0 50 100 150 200 250 300 350 SCHOTTKY FORWARD CURRENT (mA) ...
Page 5
... APD CURRENT (A) Current Monitor Transient Response (Rising Edge 1mA APD I = 10μA APD INPUT RESPONSE T < 100ns RD 50ns/DIV 1.2 LT3571 T = 25°C, unless otherwise specifi ed. A Current Monitor Accuracy MONIN 75V MONIN –1 –2 –3 – ...
Page 6
... LT3571 PIN FUNCTIONS NC (Pin 1): No Connect. APD (Pin 2): APD Cathode Pin. Connect APD cathode to this pin. MONIN (Pin 3): Current Monitor Power Supply Pin. An external lowpass fi lter can be included here to further reduce supply voltage ripple. This pin also serves as the inverting input of the current sense amplifi er. Put a sense ...
Page 7
... COMPARATOR SOFT-START RAMP GENERATOR 2MHz TO 250kHz OSCILLATOR + – FREQ ADJUST Figure 1. Block Diagram LT3571 R L1 SENSE MONIN OUT SW – MAIN SWITCH DRIVER MAIN S SWITCH PWM ...
Page 8
... The LT3571 has an integrated high side APD current monitor with a 5:1 ratio. The voltage drop across the MONIN pin and APD pin is fi xed at 5V. The MONIN pin can accept a supply voltage up to 75V, which is suitable for APD photodiode applications ...
Page 9
... CTRL pin should be held higher than 1.2V, which can be done by tying (k) T When the CTRL pin is between 0V and 1V, the LT3571 will 56.2 regulate the output such that the FB pin voltage is equal 26.1 to the CTRL pin voltage. To set the output voltage, select 12 ...
Page 10
... OUT 10 Either ceramic or solid tantalum capacitors may be used for the input decoupling capacitor, which should be placed as close as possible to the LT3571. A 1μF capacitor is suffi cient for most applications. Phase Lead Capacitor A small value capacitor (i.e., 10pF to 22pF) can be added in parallel with the resistor between the output and the FB ...
Page 11
... At greater than 10μA, the LT3571 APD current mirror typically has several hundred nanoseconds response time. To measure such fast transient response, any capacitor at the APD and the MON pin should be removed ...
Page 12
... LT3571 APPLICATIONS INFORMATION Setting APD Current Limit The LT3571 has a unique current loop to limit the APD current. Choose the sense resistor R and MONIN pins to set the APD current limit by using the following formula: 200mV R = SENSE 1.2 × I (mA) + 0.3mA APD where I is the APD current limit. ...
Page 13
... CTRL LT3571 MONIN EXTERNAL FB MON GND SYNC R APD 10nF 49.9Ω T 33.2k R3 400kHz 10k 3571 TA06 LT3571 R SENSE 20Ω 10nF 1M R2 13.7k C2 0.22μF 69V, 2mA C4 0.1μF 3571 TA05 Input Power vs APD Current 500 450 400 350 300 250 200 ...
Page 14
... APD CURRENT (mA 15μH R5 30. SHDN OFF 49.9k REF R6 R8 100k LT3571 MONIN 36.5k CTRL 0.1μF SYNC GND MON APD R T 33.2k 400kHz R3 C5 10k 10nF Q1 PHILIPS PEMT1 1.5 2 3571 TA09 V OUT R SENSE 50Ω ...
Page 15
... UD Package 16-Lead Plastic QFN (3mm × 3mm) (Reference LTC DWG # 05-08-1691) 0.70 0.05 PACKAGE OUTLINE 0.25 0.05 0.50 BSC 0.75 0.05 (4 SIDES) 1.45 0.10 (4-SIDES) 0.200 REF 0.00 – 0.05 LT3571 BOTTOM VIEW—EXPOSED PAD PIN 1 NOTCH R = 0.20 TYP R = 0.115 OR 0.25 45 CHAMFER TYP 15 16 0.40 0. (UD16) QFN 0904 0.25 0.05 0.50 BSC 3571f ...
Page 16
... TYPICAL APPLICATIONS 3.3V to 50V APD Bias Power Supply L1 10μ 3. SHDN OFF REF 1μF CTRL LT3571 MONIN R T SYNC GND MON APD 26.1k 10k 500kHz L1: TDK VLF3010AT-100MR49 C1: MURATA X7R GRM21BR71C105KA01B C2, C3: MURATA X7R GRM188R72A104KA35 Transient Response on Input Signal Falling Edge (1mA to 10μ ...