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BQ24740 Datasheet(PDF) 5 Page - Texas Instruments

Part No. BQ24740
Description  Host-controlled Multi-chemistry Battery Charger with Low Input Power Detect
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Maker  TI [Texas Instruments]
Homepage  http://www.ti.com
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BQ24740 Datasheet(HTML) 5 Page - Texas Instruments

 
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bq24740
SLUS736 – DECEMBER 2006
Table 1. TERMINAL FUNCTIONS – 28-PIN QFN
TERMINAL
DESCRIPTION
NAME
NO.
CHGEN
1
Charge enable active-low logic input. LO enables charge. HI disables charge.
Adapter current sense resistor, negative input. An optional 0.1-
µF ceramic capacitor is placed from ACN pin to AGND
ACN
2
for common-mode filtering. An optional 0.1-
µF ceramic capacitor is placed from ACN to ACP to provide
differential-mode filtering.
ACP
3
Adapter current sense resistor, positive input. (See comments with ACN description)
Low power mode detect active-high open-drain logic output. Place a 10-k
Ω pullup resistor from LPMD pin to the
pullup-voltage rail. Place a positive-feedback resistor from LPMD pin to LPREF pin for programming hysteresis (see
LPMD
4
design example for calculation). The output is HI when IADAPT pin voltage is lower than LPREF pin voltage. The
output is LO when IADAPT pin voltage is higher than LPREF pin voltage.
Adapter detected voltage set input. Program the adapter detect threshold by connecting a resistor divider from
adapter input to ACDET pin to AGND pin. Adapter voltage is detected if ACDET-pin voltage is greater than 2.4 V. The
ACDET
5
IADAPT current sense amplifier is active when the ACDET pin voltage is greater than 0.6 V. Input overvoltage, ACOV,
disables charge and ACDRV when ACDET > 3.1 V. ACOV does not latch
Adapter current set input. The voltage ratio of ACSET voltage versus VDAC voltage programs the input current
regulation set-point during Dynamic Power Management (DPM). Program by connecting a resistor divider from VDAC
ACSET
6
to ACSET to AGND; or by connecting the output of an external DAC to the ACSET pin and connect the DAC supply
to the VDAC pin.
Low power voltage set input. Connect a resistor divider from VREF to LPREF and AGND to program the reference for
the LOPWR comparator. The LPREF-pin voltage is compared to the IADAPT-pin voltage and the logic output is given
LPREF
7
on the LPMD open-drain pin. Connecting a positive-feedback resistor from LPREF pin to LPMD pin programs the
hysteresis.
Enable IADAPT to enter sleep mode; active-low logic input. Allows low Iq sleep mode when adapter not detected.
Logic low turns off the Input Current Sense Amplifier (IADAPT) when adapter is not detected and ACDET pin is <0.6
IADSLP
8
V - allows lower battery discharge current. Logic high keeps IADAPT current-sense amplifier on when adapter is not
detected and ACDET pin is <0.6 V - this allows measuring battery discharge current.
Analog ground. On PCB layout, connect to the analog ground plane, and only connect to PGND through the power
AGND
9
pad underneath the IC.
3.3-V regulated voltage output. Place a 1-
µF ceramic capacitor from VREF to AGND pin close to the IC. This voltage
VREF
10
could be used for ratiometric programming of voltage and current regulation.
Charge voltage set reference input. Connect the VREF or external DAC voltage source to the VDAC pin. Battery
voltage, charge current, and input current are programmed as a ratio of the VDAC pin voltage versus the VADJ,
VDAC
11
SRSET, and ACSET pin voltages, respectively. Place resistor dividers from VDAC to VADJ, SRSET, and ACSET pins
to AGND for programming. A DAC could be used by connecting the DAC supply to VDAC and connecting the output
to VADJ, SRSET, or ACSET.
Charge voltage set input. The voltage ratio of VADJ voltage versus VDAC voltage programs the battery voltage
regulation set-point. Program by connecting a resistor divider from VDAC to VADJ, to AGND; or, by connecting the
VADJ
12
output of an external DAC to VADJ, and connect the DAC supply to VDAC. VADJ connected to REGN programs the
default of 4.2 V per cell.
Valid adapter active-low detect logic open-drain output. Pulled low when input voltage is above ACDET programmed
EXTPWR
13
threshold, OR input current is greater than 1.25 A with 10-m
Ω sense resistor. Connect a 10-kΩ pullup resistor from
EXTPWR pin to pullup supply rail.
Synchronous mode voltage set input. Place a resistor from ISYNSET to AGND to program the charge undercurrent
ISYNSET
14
threshold to force non-synchronous converter operation at low output current, and to prevent negative inductor
current. Threshold should be set at greater than half of the maximum inductor ripple current (50% duty cycle).
Adapter current sense amplifier output. IADAPT voltage is 20 times the differential voltage across ACP-ACN. Place a
IADAPT
15
100-pF or less ceramic decoupling capacitor from IADAPT to AGND.
Charge current set input. The voltage ratio of SRSET voltage versus VDAC voltage programs the charge current
SRSET
16
regulation set-point. Program by connecting a resistor divider from VDAC to SRSET to AGND; or by connecting the
output of an external DAC to SRSET pin and connect the DAC supply to VDAC pin.
Battery voltage remote sense. Directly connect a kelvin sense trace from the battery pack positive terminal to the BAT
BAT
17
pin to accurately sense the battery pack voltage. Place a 0.1-
µF capacitor from BAT to AGND close to the IC to filter
high-frequency noise.
Charge current sense resistor, negative input. An optional 0.1-
µF ceramic capacitor is placed from SRN pin to AGND
SRN
18
for common-mode filtering. An optional 0.1-
µF ceramic capacitor is placed from SRN to SRP to provide
differential-mode filtering.
SRP
19
Charge current sense resistor, positive input. (See comments for SRN.)
CELLS
20
2, 3 or 4 cells selection logic input. Logic low programs 3 cell. Logic high programs 4 cell. Floating programs 2 cell.
5
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