Datasheet ADM7170 (Analog Devices) - 5

Data Sheet ADM7170 ABSOLUTE MAXIMUM RATINGS Table 4.
PCB material, layout, and environmental conditions. The
Parameter Rating
specified values of θJA are based on a 4-layer, 4 in. × 3 in. circuit VIN to GND −0.3 V to +7 V board. See JESD51-7 and JESD51-9 for detailed information on the board construction. For additional information, see the VOUT to GND −0.3 V to VIN AN-617 Application Note, Wafer Level Chip Scale Package, EN to GND −0.3 V to +7 V available at www.analog.com. SS to GND −0.3 V to VIN SENSE to GND −0.3 V to +7 V ΨJB is the junction-to-board thermal characterization parameter Storage Temperature Range −65°C to +150°C with units of °C/W. ΨJB of the package is based on modeling and Operating Junction Temperature Range −40°C to +125°C calculation using a 4-layer board. The JESD51-12, Guidelines for Soldering Conditions JEDEC J-STD-020 Reporting and Using Electronic Package Thermal Information, Stresses at or above those listed under Absolute Maximum states that thermal characterization parameters are not the same Ratings may cause permanent damage to the product. This is a as thermal resistances. ΨJB measures the component power stress rating only; functional operation of the product at these flowing through multiple thermal paths rather than a single or any other conditions above those indicated in the operational path as in thermal resistance, θJB. Therefore, ΨJB thermal paths section of this specification is not implied. Operation beyond include convection from the top of the package as wel as the maximum operating conditions for extended periods may radiation from the package, factors that make ΨJB more useful affect product reliability. in real-world applications. Maximum junction temperature (TJ) is calculated from the board temperature (TB) and power
THERMAL DATA
dissipation (PD) using the formula Absolute maximum ratings apply individual y only, not in TJ = TB + (PD × ΨJB) combination. The ADM7170 can be damaged when the See JESD51-8 and JESD51-12 for more detailed information junction temperature limits are exceeded. Monitoring ambient about Ψ temperature does not guarantee that T JB. J is within the specified temperature limits. In applications with high power dissipation
THERMAL RESISTANCE
and poor thermal resistance, the maximum ambient temperature θJA, θJC, and ΨJB are specified for the worst-case conditions, that may need to be derated. is, a device soldered in a circuit board for surface-mount In applications with moderate power dissipation and low packages. printed circuit board (PCB) thermal resistance, the maximum
Table 5. Thermal Resistance
ambient temperature can exceed the maximum limit provided that the junction temperature is within specification limits. The
Package Type θJA θJC ΨJB Unit
junction temperature (T 8-Lead LFCSP 36.4 23.5 13.3 °C/W J) of the device is dependent on the ambient temperature (TA), the power dissipation of the device (PD), and the junction-to-ambient thermal resistance of the
ESD CAUTION
package (θJA). Maximum junction temperature (TJ) is calculated from the ambient temperature (TA) and power dissipation (PD) using the formula T J = TA + (PD × θJA) Junction-to-ambient thermal resistance (θJA) of the package is based on modeling and calculation using a 4-layer board. The junction-to-ambient thermal resistance is highly dependent on the application and board layout. In applications where high maximum power dissipation exists, close attention to thermal board design is required. The value of θJA may vary, depending on Rev. D | Page 5 of 23 Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION TYPICAL APPLICATION CIRCUIT REVISION HISTORY SPECIFICATIONS INPUT AND OUTPUT CAPACITOR, RECOMMENDED SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS THERMAL DATA THERMAL RESISTANCE ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION APPLICATIONS INFORMATION ADIsimPOWER DESIGN TOOL CAPACITOR SELECTION Output Capacitor Input Bypass Capacitor Input and Output Capacitor Properties PROGRAMMABLE PRECISION ENABLE UNDERVOLTAGE LOCKOUT SOFT START NOISE REDUCTION OF THE ADM7170 IN ADJUSTABLE MODE EFFECT OF NOISE REDUCTION ON START-UP TIME CURRENT-LIMIT AND THERMAL OVERLOAD PROTECTION THERMAL CONSIDERATIONS TYPICAL APPLICATIONS CIRCUITS PRINTED CIRCUIT BOARD LAYOUT CONSIDERATIONS OUTLINE DIMENSIONS ORDERING GUIDE