LT1776 ELECTRICAL CHARACTERISTICSThe ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25 ° C.VIN = 40V, VSW open, VCC = 5V, VC = 1.4V unless otherwise noted.SYMBOLPARAMETERCONDITIONSMINTYPMAXUNITSTiming f Switching Frequency 180 200 220 kHz ● 170 230 kHz Maximum Switch Duty Cycle ● 85 90 % tON(MIN) Minimum Switch On Time High dV/dt Mode, RL = 39Ω (Note 4) 300 ns Boost Operation VC Pin Boost Threshold 1.35 V dV/dt Below Threshold 0.2 V/ns dV/dt Above Threshold 1.6 V/ns Sync Function Minimum Sync Amplitude ● 1.5 2.2 V Synchronization Range (Note 6) ● 250 400 kHz SYNC Pin Input R 40 kΩ SHDN Pin Function VSHDN Shutdown Mode Threshold 0.5 V ● 0.2 0.8 V Upper Lockout Threshold Switching Action On 1.260 V Lower Lockout Threshold Switching Action Off 1.245 V ISHDN Shutdown Pin Current VSHDN = 0V 12 20 µA VSHDN = 1.25V 2.5 10 µA Note 1: Absolute Maximum Ratings are those values beyond which the life Note 5: Parts are guaranteed to survive 60V on VIN and VSW. However, of a device may be impaired. thermal constraints will limit VIN in some applications, depending primarily Note 2: Control circuitry powered from V on maximum output current and switching frequency. See Applications CC. Note 3: Switch current limit is DC trimmed and tested in production. section for more information. Inductor dl/dt rate will cause a somewhat higher current limit in actual Note 6: Internal oscillator is guaranteed to sync up to 400kHz. However, application. thermal constraints and/or controllability issues may place a lower limit on Note 4: Minimum switch on time is production tested with a 39Ω resistive switching frequency in actual usage. See Applications section for more load to ground. information. 3
