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ACT2861QI Datenblatt(PDF) 43 Page - Active-Semi, Inc |
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ACT2861QI Datenblatt(HTML) 43 Page - Active-Semi, Inc |
43 / 91 page ACT2861QI Rev 2.0, 27-Apr-2018 Innovative PowerTM www.active-semi.com ActiveSwitcherTM is a trademark of Active-Semi Copyright © 2018 Active-Semi, Inc. 43 HIZ bit = 1 OTG_EN bit = 0 nOTG pin = 1 OTG_EN_OVERRIDE bit = 0 OTG to HIZ Mode OTG_VOUT_OV bit = 1 100ms deglitch Figure 15: Conditions to Enter HIZ Mode from OTG Mode OTG Output Voltage Setting The OTG output voltage is programmable between 2.96V and 23.42V in 20mV steps via by I2C bits OTG_VOUT[9:0] in registers 0x13h and 0x14h. 2.96 20 ∗ _ 9: 0 Where VOTG_VOUT[9:0] is the decimal equivalent of the value in this register. For example, if OTG_VOUT[9:0] = 0111000100b (452 decimal), the output voltage = 2.96V + 0.02V * 452 = 12.00V. When changing from one OTG output voltage to an- other, the slew rate is programmable between 1V/ms and 0.1V/ms by I2C bits OTG_OUTPUT_SLEW[1:0] in register 0x10h. This allows the output to conform to QC2.0/QC3.0/USB PD functions for higher output volt- ages. The battery voltage must always stay above VOTG_VBAT_CUFOFF set by I2C bits OTG_VBAT_CUT- OFF[2:0] in register 0x0Fh. If the battery voltage drops below this value, the IC turns of the OTG output and goes to the OTG_RST state. OTG Active Discharge When changing the OTG output voltage to a higher level, the switcher ramps the output voltage by the pro- grammed slew rate. When the output voltage is pro- grammed from a higher to a lower voltage, the voltage drops at a rate determined by the output capacitance and the load current. To minimize the fall time in no-load conditions, the ACT2861 can provide a 70mA sink when the output is transitioning to a lower output voltage. En- able this feature by writing 1 into I2C bit OTG_PULL- DOWN_RAMP. The 70mA load turns on until the output voltage goes into regulation. OTG Enable Delay Once the OTG has the valid conditions for startup, the OTG Enable Delay timer is enabled. The timer options allow a 0ms to 1s delay. The OTG startup delay is con- trolled by the I2C bits OTG_EN_DLY[1:0] OTG Mode Soft Start After the OTG Enable Delay has completed, the IC starts the output using a soft start function programma- ble by the I2C bits OTG_SS in register 0x0Eh. The softstart time is independent of the output voltage set- ting. OTG Mode Constant Output Current Regulation After OTG mode soft start has completed, the IC moni- tors the current on VIN input side sense resistor (ISRP and ISRN) to provide constant current protection and regulation in OTG mode. When the OTG output current exceeds programmed value set by the ILIM pin and the OTG_CC register, the switching converter changes to output constant current mode and regulates a fixed out- put current. In this case, the output voltage may drop if the load resistance continues to decrease. The maximum OTG output current is set by the same resistor as the charger input current, Rcs_IN. Rcs_IN must be set for the larger of the charge current or OTG cur- rent. The maximum allowable OTG output current is 5A. The actual output current limit, IOTG_OUT_LIM can be scaled between 1% to 100% of IILIM in 1% steps. The following equation defines the final OTG output current limit. _ _ ∗ _ 6: 0 Where IILIM is the hardware programmed current limit (see the Charging – Maximum Input Current section for details) and OTG_CC[6:0] is the scaling factor. OTG_CC[6:0] is the decimal equivalent value in this register. For example, if IILIM, is programmed to 5A and OTG_CC[6:0] = 0111100b (60% decimal), the final charge current = 5A * 0.60 = 3A. Note that OTG_CC[6:0] is a 7 bit register and can be programmed between 0x00h and 0x7Fh (0% and 127%). If a value of 0x00h is written to the register, the register retains 0x00h, but the IC sets the OTG scaling factor to 1%. If a value above 0x64h (100%) is written to the register, the IC retains the value, but sets the scal- ing factor to 100% The OTG regulation mode can be monitored in real time by I2C bit OTG_Output_CC in register 0x20h. When this bit = 0, the IC is regulating in output constant voltage mode. When this bit = 1, the IC is regulating in constant current mode. If the output drops below 3V, the IC as- sumes an output fault has occurred and disables the output for 3s. This is the OTG_HICCUP state. After 3s, the state machine goes to OTG_RST and restarts. If a short or high current fault is present after the restart, the IC cycles back to OTG_HICCUP and OTG_RST. This |
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