drewhamiltonasdf
New member
Hi all,
I am working on a project that requires power by single-cell LiFePO4. I have selected a number of chips for the supply/charging circuitry, but I'm having trouble making sense of what kind of power the Teensy 4 needs to operate properly.
Currently I have designed the circuit with the following:
-Battery Charger: MCP73123
-TPS65130: Dual supply DC-DC converter to supply some OP-amps in the circuit
-1-cell Fuel Gauge/Protector: DS2784
It is my understanding that I will need to cut the trace connecting Vin and power from the USB if I intend to charge the board externally. This poses two questions for me:
1. Do I need to have a boost to 5V to supply USB_VBUS if I intend to use the USB? The power to USB looks like it is hardwired to Vin, but I also see a little VUSB powerflag that makes me think maybe I can power that bus from USB and power the board externally from the battery. I'm sure this is plain as day to anyone reading this, but I nosed around on the forums and I wasn't completely clear about this.
2. What is the lowest Vin that the Teensy would run off if we forget about USB? The iMXRT1060 datasheet makes it look much lower than I think it really is. Let's assume for the sake of argument that there is nothing else externally in my circuit that relies on exact 3.3V logic. For example I have a differential input ADC that can do I2C with logic high essentially as low as 2.7V. If I can power the board with a lower voltage like this, I get rid of a bunch of power supply junk on my board.
I see from the i.MXRT1060 electrical specifications datasheet (pg. 20):
Table 7. Absolute maximum ratings:
---------------------------------------------------------------------------
Parameter Description Symbol Min Max Unit
----------------------------------------------------------------------------
Core supplies input voltage VDD_SOC_IN -0.3 -> 1.6 V
VDD_HIGH_IN supply voltage VDD_HIGH_IN -0.3 -> 3.7 V
Power for DCDC DCDC_IN -0.3 -> 3.6 V
Supply input RTC/storage VDD_SNVS_IN -0.3 -> 3.6 V
USB VBUS supply USB_OTG1/2_VBUS ---- -> 5.5 V
Supply for 12-bit ADC VDDA_ADC -0.3 -> 3.6 V
I am working on a project that requires power by single-cell LiFePO4. I have selected a number of chips for the supply/charging circuitry, but I'm having trouble making sense of what kind of power the Teensy 4 needs to operate properly.
Currently I have designed the circuit with the following:
-Battery Charger: MCP73123
-TPS65130: Dual supply DC-DC converter to supply some OP-amps in the circuit
-1-cell Fuel Gauge/Protector: DS2784
It is my understanding that I will need to cut the trace connecting Vin and power from the USB if I intend to charge the board externally. This poses two questions for me:
1. Do I need to have a boost to 5V to supply USB_VBUS if I intend to use the USB? The power to USB looks like it is hardwired to Vin, but I also see a little VUSB powerflag that makes me think maybe I can power that bus from USB and power the board externally from the battery. I'm sure this is plain as day to anyone reading this, but I nosed around on the forums and I wasn't completely clear about this.
2. What is the lowest Vin that the Teensy would run off if we forget about USB? The iMXRT1060 datasheet makes it look much lower than I think it really is. Let's assume for the sake of argument that there is nothing else externally in my circuit that relies on exact 3.3V logic. For example I have a differential input ADC that can do I2C with logic high essentially as low as 2.7V. If I can power the board with a lower voltage like this, I get rid of a bunch of power supply junk on my board.
I see from the i.MXRT1060 electrical specifications datasheet (pg. 20):
Table 7. Absolute maximum ratings:
---------------------------------------------------------------------------
Parameter Description Symbol Min Max Unit
----------------------------------------------------------------------------
Core supplies input voltage VDD_SOC_IN -0.3 -> 1.6 V
VDD_HIGH_IN supply voltage VDD_HIGH_IN -0.3 -> 3.7 V
Power for DCDC DCDC_IN -0.3 -> 3.6 V
Supply input RTC/storage VDD_SNVS_IN -0.3 -> 3.6 V
USB VBUS supply USB_OTG1/2_VBUS ---- -> 5.5 V
Supply for 12-bit ADC VDDA_ADC -0.3 -> 3.6 V