BQ24702_16 Datasheet, PDF (27/37 Pages) Texas Instruments – MULTICHEMISTRY BATTERY CHARGER CONTROLLER

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bq24702
bq24703
SLUS553E – MAY 2003 – REVISED OCTOBER 2007
TYPICAL CHARACTERISTICS (continued)
BATTERY CURRENT SET ACCURACY
vs
BATTERY CURRENT SET VOLTAGE
25
SRSET Full Scale = 2.5 V
= Max Programmed Current
20 ^{TJ = 25°C}
AC CURRENT SET ACCURACY
vs
AC CURRENT SET VOLTAGE
25
ACSET Full Scale = 2.5 V
= Max Programmed Current
T_J = 25°C
20
15
15
10
10
5
5
0
0.25
0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5
V_SRSET − Battery Current Set Voltage − V
Figure 12.
0
0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5
V_ACSET − AC Current Set Voltage − V
Figure 13.
BOARD LAYOUT GUIDELINES
Recommended Board Layout
Follow these guidelines when implementing the board layout:
1. Do not place lines and components dedicated to battery/adapter voltage sensing (ACDET,BATDEP, VS),
voltage feedback loop (BATP, BATSET if external reference is used) and shunt voltage sensing
(SRP/SRN/ACP/ACN) close to lines that have signals with high dv/dt (PWM, BATDRV, ACDRV, VHSP) to
avoid noise coupling.
2. Add filter capacitors for SRP/SRN (C8) and ACP/ACN (C3) close to IC pins
3. Add Reference filter capacitor C1 close to IC pins
4. Use an isolated, clean ground for IC ground pin and resistive dividers used in voltage sensing; use an
isolated power ground for PWM filter cap and diode (C11/D4). Connect the grounds to the battery PACK-
and adapter GND.
5. Place C7 close to VCC pin.
6. Place input capacitor C12 close to PWM switch (U3) source and R14.
7. Position ac switch (U2) to minimize trace length from ac switch source to input capacitor C12.
8. Minimize inductance of trace connecting PWM pin and PWM external switch U3 gate
9. Maximize power dissipation planes connected to PWM switch
10. Maximize power dissipation planes connected to SRP resistor if steady state in zero volt mode is possible
11. Maximize power dissipation planes connected to D1
Copyright © 2003–2007, Texas Instruments Incorporated
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