Datasheet ADM7171 (Analog Devices) - 5

Data Sheet ADM7171 ABSOLUTE MAXIMUM RATINGS Table 4.
PCB material, layout, and environmental conditions. The specified values of θ
Parameter Rating
JA are based on a 4-layer, 4 in. × 3 in. circuit board. See JESD51-7 and JESD51-9 for detailed information on the board VIN to GND −0.3 V to +7 V construction. For additional information, see the AN-617 VOUT to GND −0.3 V to VIN Application Note, Wafer Level Chip Scale Package, available at EN to GND −0.3 V to +7 V 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, states that thermal characterization parameters are not the same Stresses at or above those listed under Absolute Maximum as thermal resistances. ΨJB measures the component power flowing Ratings may cause permanent damage to the product. This is a through multiple thermal paths rather than a single path as in stress rating only; functional operation of the product at these thermal resistance, θ or any other conditions above those indicated in the operational JB. Therefore, ΨJB thermal paths include convection from the top of the package as well as radiation from section of this specification is not implied. Operation beyond the package, factors that make ΨJB more useful in real-world the maximum operating conditions for extended periods may applications. Maximum junction temperature (TJ) is calculated affect product reliability. from the board temperature (TB) and power dissipation (PD)
THERMAL DATA
using the formula Absolute maximum ratings apply individually only, not in TJ = TB + (PD × ΨJB) combination. The ADM7171 can be damaged when the junction See JESD51-8 and JESD51-12 for more detailed information temperature limits are exceeded. Monitoring ambient temperature about ΨJB. does not guarantee that TJ is within the specified temperature limits. In applications with high power dissipation and poor
THERMAL RESISTANCE
thermal resistance, the maximum ambient temperature may θJA, θJC, and ΨJB are specified for the worst case conditions, that need to be derated. is, a device soldered in a circuit board for surface-mount packages. In applications with moderate power dissipation and low printed
Table 5. Thermal Resistance
circuit board (PCB) thermal resistance, the maximum ambient
Package Type θ
temperature can exceed the maximum limit provided that the
JA θJC ΨJB Unit
8-Lead LFCSP 36.4 23.5 13.3 °C/W junction temperature is within specification limits. The junction temperature (TJ) of the device is dependent on the ambient temperature (TA), the power dissipation of the device (PD), and
ESD CAUTION
the junction-to-ambient thermal resistance of the package (θJA). Maximum junction temperature (TJ) is calculated from the ambient temperature (TA) and power dissipation (PD) using the formula TJ = 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. E | Page 5 of 23 Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION TYPICAL APPLICATION CIRCUIT TABLE OF CONTENTS 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 ADM7171 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