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Low-dropout (LDO) Linear Regulators

Selection

Since I already have them available, I will be using the Texas Instruments LP5907 3.3V, 250mA LDO, the Texas Instruments TPS7A2450 5V, 200mA LDO. While pretty low current, the LP5907 and TPS7A2450 possess very good characteristics, such as a high PSRR and a very low quiescent current of 2.0 uA, respectively.

Since these LDOs were selected for a higher end project, I’ll also eventually select pin-compatible, lower cost and higher current LDOs for 3.3V and 5V.

Requirements

While there aren’t too many strict requirements yet, I am looking to maximize PSRR and minimize quiescent current. The only strict requirement are the following:

  • > 300 mA max current
  • Outputs 5V and 3.3V

Texas Instruments recommends the TPS7A20 as a drop-in replacement for the LP5907. If higher currents are required, TI recommends the TLV758P.

Switch Mode Power Supplies

Buck
Boost
Flyback (Buck-Boost)
Charge Pump

Selection:

Requirements:

An SMPS will be required for supplying the op amps with both positive and negative voltages.

  • Split rail +-5V
  • Low noise within audible frequency ranges
  • Does not need to supply a lot of current, probably minimum 200 mA
  • Low quiescent current

Discrete DC-DC Converters, such as the Recom RB-0505D, provide dual rail +- 5V at 1W, however, are quite pricey at $5-10 for each unit.

Battery Management System

A battery management system is required to handle charging, discharging, safety, and monitoring of one or more batteries. For my purposes, I need a BMS for just one LiFePO4, Li-ion, or LiPo cell to safely charge, safely discharge, and compute the charge level of the battery.

I will be selecting the Texas Instruments BQ29700DSER Li-ion/LiPo BMS IC for 1 cell battery protection due to its availability.

N-channel MOSFET

The BQ297XX implementation requires two N-channel MOSFETs. The example they provide is the CSD16406Q3, which features V~DS~ = 25V, Q~G~ = 5.8 nC, Q~gd~ = 1.5 nC, R~DS~ = 5.9 mOhm @ V~GS~ = 4.5V, and V~th~ = 1.8V.

Citations

  1. Horowitz, P., & Hill, W., (2015) The Art of Electronics
  2. Self, D. (2010) Small Signal Audio Design