link to page 16 LTC7821 ELECTRICAL CHARACTERISTICSThe l denotes the specifications which apply over the specified operatingjunction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = VIN_SENSE = 48V, VRUN = 5V, EXTVCC = 9V,EXT_REF = 5.6V unless otherwise noted. SYMBOLPARAMETERCONDITIONSMINTYPMAXUNITS IFLYSRC1 Current Out of SW1 During Capacitor (VSW1 – VSW3) < VIN/2, VSW3 = 12V 40 mA Balancing IFLYSNK1 Current into SW1 During Capacitor Balancing (VSW1 – VSW3) > VIN/2, VSW3 = 12V 6 mA IFLYSNK3 Current into SW3 During Capacitor Balancing (VSW1 – VSW3) < VIN/2, VSW3 = 12V 40 mA IFLYSRC3 Current Out of SW3 During Capacitor (VSW1 – VSW3) < VIN/2, VSW3 = 12V 6 mA Balancing IMID_SRC Current Out of MID During Capacitor VMID < VIN/2, VMID = VMID_SENSE = 20V 60 mA Balancing VSW1 ≥ 36V, VSW3 = 12V IMID_SNK Current into MID During Capacitor Balancing VMID > VIN/2, VMID = VMID_SENSE = 28V 40 mA VSW1 ≥ 36V, VSW3 = 12V Gate Driver TG1,2 Pull-Up ON Resistance 2 Ω Pull-Down ON Resistance 1 Ω BG1, 2 Pull-Up ON Resistance 2 Ω Pull-Down ON Resistance 1 Ω TG1,2 tr TG1, TG2 Transition Time: (Note 7) TG1,2 tf Rise Time 4 ns Fall Time 4 ns BG1,2 tr BG1, BG2 Transition Time: (Note 7) BG1,2 tf Rise Time 4 ns Fall Time 4 ns T1D TG1 Off to BG1 On 45 ns T2D TG2 Off to BG2 On 20 ns T3D TG1 Off to TG2 Off 25 ns T4D BG1 Off to TG1 On 40 ns T5D BG2 Off to TG2 On 20 ns T6D BG1 Off to BG2 Off 20 ns ton(MIN) Minimum On-Time (Note 8) 210 ns Note 1: Stresses beyond those listed under Absolute Maximum Ratings Note 5: The LTC7821 is tested in a feedback loop that servos VITH to a may cause permanent damage to the device. Exposure to any Absolute specified voltage and measures the resultant VFB. Maximum Rating condition for extended periods may affect device Note 6: Dynamic supply current is higher due to the gate charge being reliability and lifetime. delivered at the switching frequency. See Applications Information. Note 2: The LTC7821E is guaranteed to meet performance specifications Note 7: Rise and fall times are measured using 10% and 90% levels. Delay from 0°C to 85°C. Specifications over the –40°C to 125°C operating times are measured using 50% levels. junction temperature range are assured by design, characterization and Note 8: The minimum on-time condition is specified for an inductor correlation with statistical process controls. The LTC7821I is guaranteed peak-to-peak ripple current ≥ 40% of I to meet performance specifications over the full –40°C to 125°C operating MAX (see Minimum On-Time Considerations in the Applications Information section) junction temperature range. Note that the maximum ambient temperature Note 9: This IC includes overtemperature protection that is intended consistent with these specifications is determined by specific operating to protect the device during momentary overload conditions. Junction conditions in conjunction with board layout, the rated package thermal temperature will exceed 125°C when overtemperature protection is active. impedance and other environmental factors. Continuous operation above the specified maximum junction temperature Note 3: TJ is calculated from the ambient temperature TA and power may impair device reliability or permanently damage the device. dissipation PD according to the following formulas: LTC7821UH: TJ = TA + (PD • 44°C/W) Note 4: Output voltage range is guaranteed by design. For output voltage setting, read “Output Voltage Setting” and “Minimum VOUT” in the “Applications Information” section. Rev A For more information www.analog.com 5 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 Revision History Related Parts
