BQ24721 Datasheet, PDF (19/48 Pages) Texas Instruments – ADVANCED MULTI-CHEMISTRY AND MULTI-CELL SYNCHRONOUS SWITCH-MODE CHARGER AND SYSTEM POWER SELECTOR

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SIMPLIFIED BLOCK DIAGRAM
AGND VCC
VREF5
BYPASS
ACDRV
BATDRV
REFERENCE SYSTEM
− 5v ldo when ACPRES
− Power−on reset
− UVLO
− Voltage references
− Internal timebase
BYPASS SW
DRIVER
Always on
AC SW AND BAT SW DRIVERS
− break−before−make LOGIC
Always on
Always on
BYPON
ACON
ACDET
SYS
TS
ALARM
SYSTEM STATUS
COMPARATORS
− Battery depleted (1)
− AC detection (1)
− *Thermistor inserted (1)
− *Thermistor cold (2)
− *Thermistor hot (2)
− System voltage / pack voltage (2)
− VCC above pack voltage (2)
(1) always on
(2) enabled when AC is detected
LOGIC
ACOC
CHGOC
CLK, POR
− Power up/down sequencing
− Charge enable logic
− Charge enable sequencing
BDEP, ACCHG, THDET,
− System power selector logic
TCOLD, THOT ,VSHI, TERMDET, _{− System selector bbm logic}
ADPSRC, VCCGTBAT, TCMP _{− Deglitch times}
POWERON
CHARGERON
ACGOOD
Always on
TTL INPUT
BUFFER
bq24721
SLUS683 – NOVEMBER 2005
IOUT
20X
Select Adaptor current
or Charge current
Always on
SYNCHRONOUS SWITCHING
PWM CONVERTER
− current loop
− dpm loop
− voltage loop
− sync/nonsync comparator
− charge overcurrent
− comparator
− charge current reference
− dpm current reference
− break−before−make logic
− duty−cycle limited, 0% to near
100% (99.5%)
− NMOS/NMOS drivers
− Internal soft start
− PWM oscillator 300 kHz/500 kHz
Enabled only when AC is
detected and CHGEN is low
SRP
SRN
ACP
ACN
EAO
EAI
FBO
SYNP
SYNN
ISYNSET
BAT
BTST
HIDRV
PH
REGN
LODRV
PVCC
SCL
SDA
SMBUS INTERFACE
Always on
MEMORY
Always on
VREG DAC
DECODER
SBS [b1−b14] to
bq24721 [7bit +1bit]
SR IREG DAC
7BIT (1.28mV/bit)
AC IREG DAC
7BIT (1.28mV/bit)
VREG DAC
1BIT Select Cells
7BIT (6.25mV/bit)
CHGEN
PGND
Figure 52. bq24721 SBS-Like SMBus Controlled Simplified Block Diagram
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