BQ24740_07 Datasheet, PDF (26/32 Pages) Texas Instruments – Host-controlled Multi-chemistry Battery Charger with Low Input Power Detect

bq24740
SLUS736 – DECEMBER 2006
www.ti.com
APPLICATION INFORMATION (continued)
PCB Layout Design Guideline
1. It is critical that the exposed power pad on the backside of the IC package be soldered to the PCB ground.
Ensure that there are sufficient thermal vias directly under the IC, connecting to the ground plane on the
other layers.
2. The control stage and the power stage should be routed separately. At each layer, the signal ground and the
power ground are connected only at the power pad.
3. The AC current-sense resistor must be connected to ACP (pin 3) and ACN (pin 2) with a Kelvin contact. The
area of this loop must be minimized. The decoupling capacitors for these pins should be placed as close to
the IC as possible.
4. The charge-current sense resistor must be connected to SRP (pin 19), SRN (pin 18) with a Kelvin contact.
The area of this loop must be minimized. The decoupling capacitors for these pins should be placed as close
to the IC as possible.
5. Decoupling capacitors for PVCC (pin 28), VREF (pin 10), REGN (pin 24) should be placed underneath the IC
(on the bottom layer) with the interconnections to the IC as short as possible.
6. Decoupling capacitors for BAT (pin 17), IADAPT (pin 15) must be placed close to the corresponding IC pins
with the interconnections to the IC as short as possible.
7. Decoupling capacitor CX for the charger input must be placed very close to the Q4 drain and Q5 source.
Figure 32 shows the recommended component placement with trace and via locations.
(a) Top Layer
(b) Bottom Layer
Figure 32. Layout Example
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