Datasheet MAX38889 (Maxim) - 7

MAX38889 2.5V to 5.5V, 3A Reversible Buck/Boost Regulator for Backup Applications
Pin Configuration 16 TQFN
H R ISET FBS FBC FBC 12 11 10 9 SYS 13 8 LX SYS 14 7 LX GND (EXPOSED PAD) PGND 15 6 LX PGND 16 5 CAP 1 2 3 4 C B Y EN D R BKB EN
3mm x 3mm, 16 TQFN Pin Descriptions PIN NAME FUNCTION
Charger Enable Input. Drive this pin high to enable charging of the supercapacitor while VSYS 1 ENC is above the charging threshold. Drive this pin low to disable charging. If not driven, tie this pin to the SYS rail. Backup Enable Input. Drive this pin high to enable system backup when VSYS drops below 2 ENB the backup threshold. Drive this pin low to disable backup. If not driven, tie this pin to the SYS rail. Ready Status Pin. Connect a pullup resistor from RDY to a logic supply. VRDY will be pulled 3 RDY low when VFBCR is below 0.5V and released when it is above 0.5V. VRDY is pulled low when VENC and VENB are both low. Backup Status Pin. Connect a pullup resistor from BKB to a logic supply. VBKB will be pulled 4 BKB low when VFBS is regulating at 1.2V and released when it is above 1.23V. VBKB is released high when VENC and VENB are both low. Supercapacitor. Connect to a supercapacitor rated between 0.8V to 5V. Put a high-frequency 5 CAP capacitor of 22µF close to the CAP pin. Inductor Switching Node. Connect a 0.47μH inductor from LX to CAP. Keep this switching 6, 7, 8 LX node separated from feedback signal nodes FBS, FBCH, and FBCR as much as possible. 9 FBCR Supercapacitor Ready Input. RDY will go high when VFBCR reaches 0.5V. Supercapacitor Feedback Input. Connect a resistor-divider from CAP to FBCH to GND to set 10 FBCH the supercapacitor maximum charging voltage. www.maximintegrated.com Maxim Integrated | 7 Document Outline Product Highlights Key Applications Simplified Application Diagram Pin Configuration Absolute Maximum Ratings Package Information Electrical Characteristics Typical Operating Characteristics Pin Configuration Pin Descriptions Functional Diagram Detailed Description Application Circuits Supercapacitor Voltage Configuration System Voltage Configuration Charge/Discharge Current Configuration Charging Backup Applications Information Capacitor Selection Supercapacitor Selection Inductor Selection Status Flags BKB Flag RDY Flag Enabling the Device Charger Enable Input (ENC) Backup Enable Input (ENB) PCB Layout Guidelines Ordering Information