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LTC3226 Datasheet(PDF) 7 Page - Linear Technology |
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LTC3226 Datasheet(HTML) 7 Page - Linear Technology |
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7 / 16 page  LTC3226 7 3226fa PIN FUNCTIONS VOUT (Pin 1): Voltage Output. This pin is used to provide power to an external load from either the primary input supply (VIN) or the supercapacitor (CPO) if the primary input supply is not available. VOUT should be bypassed with a low ESR ceramic capacitor of at least 47μF capaci- tance to GND. PFO (Pin 2): Open-Drain Power-Fail Status Output. This pin is pulled to ground by an internal N-channel MOSFET when the PFI input is below 1.2V. Once the PFI input re- covers, this pin becomes high impedance. PFI (Pin 3): Power-Fail Input. High impedance input to an accurate comparator with a 1.2V falling threshold and 20mV hysteresis. This pin controls the state of the PFO output pin and the operating mode of the LTC3226. LDO_FB (Pin 4): Internal LDO Feedback Pin. The voltage on this pin is compared to the internal reference voltage (0.8V) by the error amplifier to keep the output in regula- tion. An external resistor divider is required between VOUT, LDO_FB and GND to program the LDO output voltage. See the Applications Information section. GATE (Pin 5): External FET Gate Pin. This pin is driven by an internal ideal diode controller to regulate VOUT to 15mV below VIN. RST_FB (Pin 6): Reset Comparator Input. High imped- ance input to an accurate comparator with a 0.74V falling threshold and 20mV hysteresis. This pin controls the state of the RST output pin. An external resistor divider is required between VOUT, RST_FB and GND. It can be the same resistor divider as the LDO_FB divider. See the Applications Information section. RST (Pin 7): Open-Drain Status Output of the RESET Comparator. This pin is pulled to ground by an internal N-channel MOSFET whenever the RST_FB pin voltage falls below 0.74V. Once the RST_FB pin voltage recovers, the pin becomes high impedance after a 290ms delay indicat- ing that VOUT is within 7.5% of its programmed value. EN_CHG (Pin 8): Enable Pin for the Charge Pump Super- capacitor Charger with an Internal Pull-Up. Tie this pin to a voltage below 0.4V to disable the internal charge pump. PROG (Pin 9): Charger Input Current Limit Programming Pin. A resistor connected between this pin and GND sets the input current limit for the charger. See the Applications Information section. CPO_FB (Pin 10): Feedback Pin for the Charge Pump. The voltage on this pin is compared to the internal reference voltage (1.2V) to keep the charge pump output CPO in regulation. An external resistor divider is required between CPO, CPO_FB and GND to program the CPO output volt- age. See the Applications Information section. CAPGOOD (Pin 11): Open-Drain Status Output of the CPO Voltage. This pin is pulled to ground by an internal N-channel MOSFET until CPO_FB pin reaches 1.11V. Once the CPO_FB pin exceeds 1.11V, this pin becomes high impedance indicating that the CPO voltage is within 7.5% of its target value. C– (Pin 12): Internal Charge Pump Flying Capacitor Negative Terminal. VIN (Pin13):PrimaryInputSupply.Thispinsuppliespower to the VOUT pin through an external P-channel MOSFET and also to the supercapacitors attached to the CPO and VMID pins. VIN should be bypassed to GND with a low ESR ceramic capacitor of at least 2.2μF depending on the load transient. VMID (Pin 14): Midpoint of Two Series Supercapacitors. C+ (Pin 15): Internal Charge Pump Flying Capacitor Positive Terminal. A 1μF to 10μF X5R or X7R ceramic capacitor should be connected from C+ to C–. CPO (Pin 16): Backup Supply Pin. Connect CPO to the top plate of the top supercapacitor. This pin receives power from VIN through an internal charge pump doubler and supplies power to VOUT through an internal LDO when the primary input supply has failed. GND (Exposed Pad Pin 17): Ground. The exposed pad should be connected to a continuous ground plane on the second layer of the printed circuit board by several vias directly under the part to achieve optimal thermal performance. |
Similar Part No. - LTC3226 |
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Similar Description - LTC3226 |
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