Datasheet MAX17577, MAX17578 (Maxim) - 14

MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters VSYNCPK_PK > 0.26 for 10% ≤ D D SYNC < 20% SYNC VSYNCPK_PK > 0.26 for 80% < D 1 − D SYNC ≤ 90% SYNC The value of CSYNC can be calculated using the following equation. CSYNC = 45 (VSYNCPK_PK)−1 where CSYNC is in pF.
MAX17577/
CSYNC
MAX17578
RT/SYNC RRT/SYNC CLOCK SOURCE SOUT GND Figure 1. Synchronization to an External Clock
Linear Regulator (VCC)
The MAX17577 and MAX17578 have an internal low dropout (LDO) regulator that is referenced to SOUT and powers VCC. This LDO is enabled during power-up or when EN/UVLO is above 0.8V (typ) with respect to GND. VCC powers internal control circuitry. Bypass VCC to SOUT with a 2.2μF low-ESR ceramic capacitor. The MAX17577 and MAX17578 commence operation when VCC > VCC-UVR (4.2V) and turns OFF when VCC < VCC-UVF (3.8V).
Operating Input-Voltage Range
The minimum operating-input voltage (VIN(MIN)) for a given output-voltage setting is calculated using the following equation. |VOUT|×(1−DMAX) VIN(MIN) = + 1.5A (R D DCR(MAX) + (1 − DMAX) × RDS − ONL(MAX) + DMAX × RDS − ONH(MAX)) MAX DMAX VIN(MIN) cannot be less than 4.5V. To comply with internal device ratings, the maximum operating-input voltage (VIN(MAX)) for a given output-voltage setting is limited to 60V - |VOUT|. For example, the maximum permissible input voltage for a -12V output specification would be 48V. Thus, the value of the VIN(MAX) is given by the following equation. |VOUT|× (1 - tON_MIN(MAX)×fSW) VIN(MAX) = Lower of (60V - |VOUT|) or tON_MIN(MAX)×fSW where: VOUT = Steady-state output voltage RDCR(MAX) = Worst-case DC-resistance of the inductor RDS-ONH(MAX) = Worst-case on-state resistance of the high-side internal MOSFET RDS-ONL(MAX) = Worst-case on-state resistance of the low-side internal MOSFET DMAX = Maximum duty cycle of the converter www.maximintegrated.com Maxim Integrated | 14 Document Outline General Description Applications Benefits and Features Simplified Application Circuit Absolute Maximum Ratings Package Information TDFN Electrical Characteristics Electrical Characteristics (continued) Typical Operating Characteristics Typical Operating Characteristics (continued) Pin Configuration MAX17577, MAX17578 Pin Description Pin Description (continued) Functional Diagrams MAX17577/MAX17578 Block Diagram Detailed Description Switching Frequency and External Clock Synchronization Linear Regulator (VCC) Operating Input-Voltage Range Overcurrent Protection (OCP)/Hiccup Mode RESET Output Prebiased Output Thermal-Shutdown Protection Applications Information Inductor Selection Load Current Capability (IOUT(MAX)) Input Capacitor Selection Output-Capacitor Selection Soft-Start Capacitor Selection Adjusting Output Voltage Setting the Input Undervoltage-Lockout Level Inductive Output Short-Circuit Protection Power Dissipation PCB Layout Guidelines Typical Application Circuits -5V Typical Application Circuits Typical Application Circuits (continued) -12V Typical Application Circuit Ordering Information Revision History