LT3570EFE-PBF LINER [Linear Technology], LT3570EFE-PBF Datasheet
LT3570EFE-PBF
Related parts for LT3570EFE-PBF
LT3570EFE-PBF Summary of contents
Page 1
FEATURES n 2.5V to 36V Input Voltage Range n Programmable Switching Frequency from 500kHz to 2MHz n Synchronizable Up to 2.75MHz 0.8V OUT(MIN) n Independent Soft-Start for Each Converter n Separate V Supplies for Each Converter IN ...
Page 2
... LT3570EUF#PBF LT3570EUF#TRPBF LT3570IUF#PBF LT3570IUF#TRPBF LT3570EFE#PBF LT3570EFE#TRPBF LT3570IFE#PBF LT3570IFE#TRPBF Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi label on the shipping container. Consult LTC Marketing for information on non-standard lead based fi nish parts. ...
Page 3
ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi cations are at T PARAMETER Minimum Operating Voltage (V ) IN1 Minimum Operating Voltage (V ) IN2 Shutdown Current (Note 4) V Quiescent Current IN1 V Quiescent Current IN2 V Quiescent Current IN3 Bias ...
Page 4
LT3570 ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi cations are at T PARAMETER SW2 Error Amplifi Transconductance Error Amplifi Voltage Gain V Pin Switching Threshold SW2 Current Gain C2 SW2 Current Limit SW2 V ...
Page 5
TYPICAL PERFORMANCE CHARACTERISTICS V Quiescent Current IN1 vs Temperature 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 –50 – 100 125 TEMPERATURE (°C) 3570 G04 Bias Pin Current vs Temperature 3.0 2.5 2.0 1.5 1.0 0.5 ...
Page 6
LT3570 TYPICAL PERFORMANCE CHARACTERISTICS SW2 Current Limit vs Duty Cycle 3.0 2.5 2.0 1.5 1.0 0 DUTY CYCLE (%) BOOST Pin Current vs Switch Current 25° ...
Page 7
PIN FUNCTIONS (QFN/TSSOP) V (Pins 1,2/Pin 14): Input Voltage for the Buck Regulator. IN2 This pin also supplies the current to the internal circuitry of the LT3570. This pin must be locally bypassed with a capacitor. SW2 (Pin 3/Pin15): Switch ...
Page 8
LT3570 BLOCK DIAGRAM 8 3570fa ...
Page 9
OPERATION The LT3570 is a constant frequency, current mode, buck converter and boost converter with an NPN LDO regula- tor. Operation can be best understood by referring to the Block Diagram. If all of the SHDN pins are held low, ...
Page 10
LT3570 APPLICATIONS INFORMATION FB Resistor Network The output voltage is programmed with a resistor divider (refer to the Block Diagram) between the output and the FB pin. Choose the resistors according to: ⎛ ⎞ V OUT R1= R2 – 1 ...
Page 11
APPLICATIONS INFORMATION to 1.2A at DC2 = 0.8. The maximum output current is a function of the chosen inductor value: Δ – OUT2(MAX) LIM2 1.5 • 1– 0.25 • DC2 Choosing an inductor value ...
Page 12
LT3570 APPLICATIONS INFORMATION and small circuit size, are therefore an option. You can estimate output ripple with the following equations: Δ for ceramic capacitors RIPPLE 8 • f • C OUT and = ΔI V • ESR ...
Page 13
APPLICATIONS INFORMATION into a tight local loop, minimizing EMI. The input capaci- tor must have low impedance at the switching frequency to do this effectively and it must have an adequate ripple current rating. The RMS input current is: ( ...
Page 14
LT3570 APPLICATIONS INFORMATION Boost Diode Selection A Schottky diode is recommended for use with the LT3570 inverter/boost regulator. The Microsemi UPS120 is a very good choice. Where the input to output voltage differen- tial exceeds 20V, use the UPS140 (a ...
Page 15
APPLICATIONS INFORMATION compensation resistor usually in the range 50k. A good technique to compensate a new application is to use a 50k potentiometer in place of R 1nF capacitor for ...
Page 16
LT3570 APPLICATIONS INFORMATION Oscillator The free-running frequency is set through a resistor from the R pin to ground. The oscillator frequency seen in Figure 4. The oscillator can be synchronized with an external clock applied to ...
Page 17
APPLICATIONS INFORMATION will be enabled again going through a soft-start cycle. Note: Overtemperature protection is intended to protect the device during momentary overload conditions. Continuous operation above the specifi ed maximum operating junction temperature may result in device degradation or ...
Page 18
LT3570 TYPICAL APPLICATIONS 28V C9 10μF SHDN1 SHDN2 SHDN3 D1 V OUT1 8V 250mA R1 105k C1 10μF R2 11.5k 10nF V IN 12V C9 10μ 47μH V OUT1 34V R1 442k C1 10μF ...
Page 19
PACKAGE DESCRIPTION 4.50 ± 0.05 2.45 ± 0.05 (4 SIDES) 3.10 ± 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 6.60 ±0.10 4.50 ±0.10 RECOMMENDED SOLDER PAD LAYOUT 0.09 – 0.20 (.0035 – .0079) NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS 2. DIMENSIONS ...
Page 20
LT3570 TYPICAL APPLICATION 12V C9 10μF V OUT1 15V 200mA C1 10μF RELATED PARTS PART NUMBER DESCRIPTION LT1767 1.5A, 1.25MHz Step-Down Switching Regulator LT1930/LT1930A 1.2MHz/2.2MHz, High Effi ciency Step-Up DC/DC SW Converter LT1939 ...