Datasheet LT8708-1 (Analog Devices) - 7

LT8708-1
ELECTRICAL CHARACTERISTICS The
l
denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25°C. VINCHIP =12V, SHDN = 3V, DIR = 3.3V unless otherwise noted. (Note 3). PARAMETER CONDITIONS MIN TYP MAX UNITS NMOS Gate Drivers
TG1, TG2 Rise Time CLOAD = 3300pF (Note 4) 20 ns TG1, TG2 Fall Time CLOAD = 3300pF (Note 4) 20 ns BG1, BG2 Rise Time CLOAD = 3300pF (Note 4) 20 ns BG1, BG2 Fall Time CLOAD = 3300pF (Note 4) 20 ns TG1 Off to BG1 On Delay CLOAD = 3300pF Each Driver 90 ns BG1 Off to TG1 On Delay CLOAD = 3300pF Each Driver 80 ns TG2 Off to BG2 On Delay CLOAD = 3300pF Each Driver 90 ns BG2 Off to TG2 On Delay CLOAD = 3300pF Each Driver 80 ns Min On-Time for Main Switch in Boost Operation (tON(M3,MIN)) Switch M3, CLOAD = 3300pF 200 ns Min On-Time for Synchronous Switch in Buck Operation (tON(M2,MIN)) Switch M2, CLOAD = 3300pF 200 ns Min Off-Time for Main Switch in Steady-State Boost Operation Switch M3, CLOAD = 3300pF 230 ns Min Off-Time for Synchronous Switch in Steady-State Buck Operation Switch M2, CLOAD = 3300pF 230 ns
Oscillator
Switch Frequency Range SYNCing or Free Running 100 400 kHz Switching Frequency, fOSC RT = 365k l 102 120 142 kHz RT = 215k l 170 202 235 kHz RT = 124k l 310 350 400 kHz SYNC High Level for Synchronization l 1.3 V SYNC Low Level for Synchronization l 0.5 V SYNC Clock Pulse Duty Cycle VSYNC = 0V to 2V 20 80 % Recommended Min SYNC Ratio fSYNC/fOSC 3/4 CLKOUT Output Voltage High VLDO33 – VCLKOUT, 1mA Out of CLKOUT Pin, 100 250 mV ILDO33 = 0µA CLKOUT Output Voltage Low 1mA Into CLKOUT Pin 25 100 mV CLKOUT Duty Cycle TJ = –40°C 22.7 % TJ = 25°C 44.1 % TJ = 125°C 77 % CLKOUT Rise Time CLOAD = 200pF 20 ns CLKOUT Fall Time CLOAD = 200pF 20 ns CLKOUT Phase Delay SYNC Rising to CLKOUT Rising, fOSC = 100kHz l 160 180 200 Degree
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
Note 5:
Do not apply a voltage or current source to these pins. They must be may cause permanent damage to the device. Exposure to any Absolute connected to capacitive loads only, otherwise permanent damage may occur. Maximum Rating condition for extended periods may affect device
Note 6:
Negative voltages on the SW1 and SW2 pins are limited, in an reliability and lifetime. application, by the body diodes of the external NMOS devices, M2 and
Note 2:
Do not force voltage on the VC pin. M3, or parallel Schottky diodes when present. The SW1 and SW2 pins
Note 3:
The LT8708E-1 is guaranteed to meet performance specifications are tolerant of these negative voltages in excess of one diode drop below from 0°C to 125°C junction temperature. Specifications over the –40°C ground, guaranteed by design. to 125°C operating junction temperature range are assured by design,
Note 7:
This IC includes overtemperature protection that is intended characterization and correlation with statistical process controls. to protect the device during momentary overload conditions. Junction The LT8708I-1 is guaranteed over the full –40°C to 125°C junction temperature will exceed the maximum operating junction temperature temperature range. The LT8708H-1 is guaranteed over the full –40°C to when overtemperature protection is active. Continuous operation above 150°C operating junction temperature range. the specified maximum operating junction temperature may impair device
Note 4:
Rise and fall times are measured using 10% and 90% levels. reliability. Delay times are measured using 50% levels.
Note 8:
Do not force voltage or current into these pins. Rev 0 For more information www.analog.com 7 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Typical Application Related Parts Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Common LT8708-1 and LT8708 Features Adding Phases to an LT8708 Application Adding Phases: The Master LT8708 Adding Phases: The Slave LT8708-1 Start-Up Start-Up: SWEN Pin Start-Up: Soft-Start of Switching Regulator Control Overview Power Switch Control Unidirectional and Bidirectional Conduction Error Amplifiers Transfer Function: IOUT(SLAVE) Vs IOUT(MASTER) Transfer Function: CCM Transfer Function: DCM, HCM and Burst Mode Operation Current Monitoring and Limiting Monitoring: IOUT(SLAVE) Monitoring and Limiting: IIN(SLAVE) Multiphase Clocking Applications Information Quick-Start Multiphase Setup Quick Setup: Design the Master Phase Quick Setup: Design the Slave Phase(s) Quick Setup: Evaluation Choosing the Total Number of Phases Operating Frequency Selection CIN and COUT Selection CIN and COUT Selection: VIN Capacitance CIN and COUT Selection: VOUT Capacitance VINHIMON, VOUTLOMON and RVSOFF Configuring the IIN(SLAVE) Current Limits Regulating IOUT(SLAVE) IOUT(SLAVE): Circuit Description IOUT(SLAVE): Configuration Loop Compensation Voltage Lockouts Circuit Board Layout Checklist Design Example Typical Applications Package Description Typical Application Related Parts