–12–

REV. 0

ADP3404

OUTLINE DIMENSIONS

Dimensions shown in inches and (mm).

28-Lead Thin Shrink Small Outline (TSSOP)

(RU-28)

0.177 (4.50)

0.169 (4.30)

28

15

14

1

0.386 (9.80)

0.378 (9.60)

0.256 (6.50)

0.246 (6.25)

PIN 1

SEATING

PLANE

0.006 (0.15)

0.002 (0.05)

0.0118 (0.30)

0.0075 (0.19)

0.0256 (0.65)

BSC

0.0433 (1.10)

MAX

0.0079 (0.20)

0.0035 (0.090)

0.028 (0.70)

0.020 (0.50)

8

0

Charger Diode Selection

The diode shown in Figure 2 is used to prevent the battery from

discharging into the charger turn-on setting resistors, R1 and R2. A

Schottky diode is recommended to minimize the voltage difference

from the charger to the battery and the power dissipation. Choose

a diode with a current rating high enough to handle both the battery

charging current and the current the ADP3404 will draw if pow-

ered up during charging. The battery charging current is dependent

on the battery chemistry, and the charger circuit. The ADP3404

current will be dependent on the loading.

Printed Circuit Board Layout Considerations

Use the following general guidelines when designing printed

circuit boards:

1. Split the battery connection to the VBAT and SIMBAT pins

of the ADP3404. Use separate traces for each connection

and locate the input capacitors as close to the pins as possible.

2. SIM input and output capacitors should be returned to the

SIMGND and kept as close as possible to the ADP3404 to

minimize noise. Traces to the SIM charge pump capacitor

should be kept as short as possible to minimize noise.

3. VCCA and VTCXO capacitors should be returned to AGND.

4. VCC and VRTC capacitors should be returned to DGND.

5. Split the ground connections. Use separate traces or planes for

the analog, digital, and power grounds, and tie them together

at a single point, preferably close to the battery return.