Datasheet LTC7812 (Analog Devices) - 36

LTC7812
APPLICATIONS INFORMATION Table 1. Summary of Trade-Offs in Determining the VMID Voltage in a Cascaded Boost+Buck Regulator A B C D
Option VMID_REG > VOUT_REG and VIN_MIN_OP < VOUT_REG < VMID_REG = VIN_MIN_OP and VIN_MIN_OP > VMID_REG > VMID_REG > VIN_MAX_OP VMID_REG < VIN_MAX_OP VOUT_REG = VIN_MAX_OP VOUT_REG (Pass-Through /Wire Mode) Example for Normal Input VMID_REG = 18V VMID_REG =14V VMID_REG = 10V VMID_REG = 10V Operating Range of 10V – 16V VOUT = VOUT_REG = 12V VOUT = VOUT_REG = 12V VOUT_REG = 16V VOUT = VOUT_REG = 5V (VIN_MIN_OP = 10V VOUT = 10V – 16V VIN_MAX_OP = 16) with a Full Range of 2.5V – 38V Boost Boosting in Normal Yes, Over Full Range Yes, When VIN < VMID_REG No No Operating Range? Buck Bucking in Normal Yes, Over Full Range Yes, Over Full Range No, in Dropout Yes, Over Full Range Operating Range? LTC7812 No-Load Quiescent 33µA 33µA ~3mA 33µA Current in Burst Mode Operation Heavy Load Efficiency Slightly Lower High When Not Boosting; Highest High Slightly Lower When Boosting Input Ripple Low Low When Boosting; Very Extremely Low Very Low Low When Not Boosting; Some Cycle-Skipping During Transition Output Ripple Low Low Extremely Low Low EMI in Normal Operating Low Very Low When Not Boosting; Extremely Low Very Low Range Low When Boosting Example for Normal Operating VMID_REG = 18V VMID_REG =14V VMID_REG = 10V VMID_REG = 10V Range: VIN_MIN_OP = 10V – VOUT = VOUT_REG = 12V VOUT = VOUT_REG = 12V VOUT_REG = 16V VOUT = VOUT_REG = 5V VIN_MAX_OP = 16V Figure 10 Figure 9 VOUT = 10V – 16V Figure 12 Figure 11 7812fc 36 For more information www.linear.com/LTC7812 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Functional Diagram Operation Applications Information Typical Applications Typical Application Related Parts