Datasheet LT7101 (Analog Devices) - 9
| 制造商 | Analog Devices |
| 描述 | 105V, 1A Low EMI Synchronous Step-Down Regulator with Fast Current Programming |
| 页数 / 页 | 38 / 9 — TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. … |
| 文件格式/大小 | PDF / 3.2 Mb |
| 文件语言 | 英语 |
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. Radiated EMI Performance (CISPR25 Radiated
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LT7101
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. Radiated EMI Performance (CISPR25 Radiated Emission Test with Class 5 Peak Limits)
50 VERTICAL POLARIZATION 40 V/m) 30 20 AMPLITUDE (dBµ 10 CLASS 5 PEAK LIMIT LT7101 0 0 100 200 300 400 500 600 700 800 900 1000 FREQUENCY (MHz) FIGURE 17 CIRCUIT 7101 G34 48VIN TO 5VOUT AT 1A fSW = 400kHz
PIN FUNCTIONS RUN (Pin 3):
Run Control Input. Holding this pin below voltage mode is selected using the VPRG1 and VPRG2 pins. 1.1V shuts off the switching regulator. Holding this pin If VPRG1 and VPRG2 are both floating, then a resistor from below 0.7V reduces the quiescent current to approxi- RIND to SGND must be used. mately 0.7µA. Place a resistor divider between VIN and
I
this pin to use as an undervoltage lockout. Tie this pin to
TH (Pin 9):
Error Amplifier Output and Switching Regulator Compensation Point. Place compensation components VIN to always enable the LT7101. between the ITH pin and SGND. Tie this pin to INTVCC for
SGND (Pin 6):
Signal Ground. fixed internal compensation.
OVLO (Pin 7):
Overvoltage Shutdown Input. If the voltage
VFB (Pin 10):
Regulator Feedback Input. When set to on this pin exceeds 1.21V, then the switching regulator adjustable mode, use an external resistor divider between is shut down and the SS pin is internally grounded. Tie the regulator output voltage and the VFB pin. For fixed out- this pin to SGND to allow operation with VIN up to 105V. put voltage mode, tie VFB directly to the regulator output.
RIND (Pin 8):
Sets the current used to create an internal
FREQ (Pin 11):
The frequency control pin for the internal ramp that replicates the inductor current up-slope for low VCO. Connect this pin to SGND for 300kHz operation or duty cycle operation. This pin generates a voltage that to INTVCC for 1MHz operation. Place a resistor to SGND varies with the switching frequency. Place a resistor to on this pin to set the operating frequency between 200kHz SGND on this pin equal to 1/(3.3 • L) to set the internal and 2MHz. Minimize the capacitance on this pin if Burst ramp current. This pin can be left floating if fixed output Mode operation is used. This pin sources 40µA. Rev. 0 For more information www.analog.com 9 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Functional Diagram Operation Applications Information Typical Applications Package Description Typical Application Related Parts
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. Radiated EMI Performance (CISPR25 Radiated Emission Test with Class 5 Peak Limits)
50 VERTICAL POLARIZATION 40 V/m) 30 20 AMPLITUDE (dBµ 10 CLASS 5 PEAK LIMIT LT7101 0 0 100 200 300 400 500 600 700 800 900 1000 FREQUENCY (MHz) FIGURE 17 CIRCUIT 7101 G34 48VIN TO 5VOUT AT 1A fSW = 400kHz
PIN FUNCTIONS RUN (Pin 3):
Run Control Input. Holding this pin below voltage mode is selected using the VPRG1 and VPRG2 pins. 1.1V shuts off the switching regulator. Holding this pin If VPRG1 and VPRG2 are both floating, then a resistor from below 0.7V reduces the quiescent current to approxi- RIND to SGND must be used. mately 0.7µA. Place a resistor divider between VIN and
I
this pin to use as an undervoltage lockout. Tie this pin to
TH (Pin 9):
Error Amplifier Output and Switching Regulator Compensation Point. Place compensation components VIN to always enable the LT7101. between the ITH pin and SGND. Tie this pin to INTVCC for
SGND (Pin 6):
Signal Ground. fixed internal compensation.
OVLO (Pin 7):
Overvoltage Shutdown Input. If the voltage
VFB (Pin 10):
Regulator Feedback Input. When set to on this pin exceeds 1.21V, then the switching regulator adjustable mode, use an external resistor divider between is shut down and the SS pin is internally grounded. Tie the regulator output voltage and the VFB pin. For fixed out- this pin to SGND to allow operation with VIN up to 105V. put voltage mode, tie VFB directly to the regulator output.
RIND (Pin 8):
Sets the current used to create an internal
FREQ (Pin 11):
The frequency control pin for the internal ramp that replicates the inductor current up-slope for low VCO. Connect this pin to SGND for 300kHz operation or duty cycle operation. This pin generates a voltage that to INTVCC for 1MHz operation. Place a resistor to SGND varies with the switching frequency. Place a resistor to on this pin to set the operating frequency between 200kHz SGND on this pin equal to 1/(3.3 • L) to set the internal and 2MHz. Minimize the capacitance on this pin if Burst ramp current. This pin can be left floating if fixed output Mode operation is used. This pin sources 40µA. Rev. 0 For more information www.analog.com 9 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Functional Diagram Operation Applications Information Typical Applications Package Description Typical Application Related Parts