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# <a name="Lithium Ion Battery Charging ICs"></a> Lithium Ion Battery Charging ICs

<table border=1 cellpadding=0 cellspacing=0>
  <tr>
    <th bgcolor="#99CCCC"><strong> Up: </strong></th>
    <td>[[AvionicsPowerSystemLv2]]</td>
  </tr>
  <tr>
    <th bgcolor="#99CCCC"><strong> Xref: </strong></th>
    <td align="right">[[BatteryPackLv2]], [[PowerUseageLv2]], [[BatteryPack]]</td>
  </tr>
</table>

**_Requirements:_**

1. Recharges a 4 cell Li Ion pack (14.4V nominal, 16.8V max)
2. Minimal parts count - and especially no weird resistor needed
3. Minimum design time on circuit - i.e., clear application notes
4. Vaguely modern - no "crufty" chips
5. Small footprint

**_So far:_**

[Linear Technology](http://www.linear.com/) LTC4006: <http://www.linear.com/prod/datasheet.html?datasheet=1001>

- High Conversion Efficiency: Up to 96%
- Output Currents Exceeding 4A
- ±0.8% Accurate Preset Voltages: 8.4V, 12.6V, 16.8V
- Built-In Charge Termination with Automatic Restart
- AC Adapter Current Limiting Maximizes Charge Rate\*
- Automatic Conditioning of Deeply Discharged Batteries
- Thermistor Input for Temperature Qualified Charging
- Wide Input Voltage Range: 6V to 28V
- 0.5V Dropout Voltage; Maximum Duty Cycle: 98%
- Programmable Charge Current: ±5% Accuracy
- Indicator Outputs for Charging, C/10 Current Detection and AC Adapter Present
- Charging Current Monitor Output
- 16-Pin Narrow SSOP Package

This looks pretty good. We can also combine it with the LTC4412 "ideal diode" - it replaces a BASD (big ass schottkey diode) with a SOT23-6 IC (using only 11uA) and a MOSFET... which with a 0.01 ohm MOSFET saves us 0.3V drop \* 4A - 4A^2 \* 0.01 ohm = 1.0 watts!!!

SIMILAR: <http://www.linear.com/prod/datasheet.html?datasheet=947>

Maxim equivalent: the MAX745 - <http://pdfserv.maxim-ic.com/en/ds/MAX745.pdf>

Battery fuel gage: [http://www.maxim-ic.com/quick\_view2.cfm?qv\_pk=1793&amp;ln=](http://www.maxim-ic.com/quick_view2.cfm?qv_pk=1793&ln=)

----

[Linear Technology](http://www.linear.com/) LT1513: <http://www.linear.com/prod/datasheet.html?datasheet=346>

- Continuous charge current of 2A for 4.1V cells
- Peak output current of 3A
- Fixed or programmable charge current
- ±1% accuracy in fixed voltage mode
- Charges any number of cells up to 20V
- Accomodates topologies that charge batteries with voltages above supply voltage
- 500 KHz switching frequency allows for use of small, less expensive inductors

One of the pros of this part is its ability to boost its input voltage to provide a higher charging voltage. However, the data sheet indicates that at higher voltages the charging current of the LT1513 drops. Charging a cell at 16 volts, for example, the LT1513 can only provide 1 amp. In our situation this means it would take about five hours to charge the currently planned battery pack for the LV2 rocket payload. A closer to ideal charging chip would provide boost capability from, say, 18 VDC out given 12 VDC supply at 4A. We'll look a little longer, but probably won't find a chip that meets these specifications.

----

Other chips:

- MAX1737: [http://www.maxim-ic.com/quick\_view2.cfm/qv\_pk/2217](http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2217)
- Maxim IC parametric search: [http://para.maxim-ic.com/ss.asp?Fam=Batt\_Chrg](http://para.maxim-ic.com/ss.asp?Fam=Batt_Chrg)
- MAX1909: nice chip, switched diodes, lots of nice options, hot swap pack, BUT: requires host.

----

Parts:

- <http://www.fairchildsemi.com/ds/ND/NDS8947.pdf>
- <http://www.searchdatasheets.com/download/55cf936f85383117311f92fb014468dd.pdf>

----

**_Interesting but possibly not applicable:_**

<http://www.linear.com/prod/datasheet.html?datasheet=1048>: a smart battery charger that DOESN'T NEED a host to operate! That's very, very interesting... we could use a smart battery with very little impact on ourselves - let the battery charge itself and then add charging software later. For example, a Dell 7000/7500 uses a 14.8 V 5.1 Ah smart battery... we could plug that into this smart charger and everthing might just "work".... uh huh, sure.