BQ25040 Datasheet, PDF (15/25 Pages) Texas Instruments – 1.1A, Single-Input, Single Cell Li-Ion Battery Charger With 50mA LDO and 2.3A Production Test Support

bq25040
www.ti.com ...................................................................................................................................................... SLUS910B – MARCH 2009 – REVISED MARCH 2009
Input Current Limit (ISET, EN/SET)
The fast charge current is programmed using the EN/SET and ISET inputs. The EN/SET input allows the user to
select USB100 mode, USB500 mode, or the user programmable current set by ISET. The user programmable
current is set by connecting a resistor from ISET to VSS. The value of the resistor is determined by:
R_{IS ET} =
K_ISET
I_{CH G}
(1)
The fast charge current (I_CHG) must be programmed between 100mA and 1.1A. If the current at ISET is
programmed to be less than the USB500 current limit, the current will be limited to the ISET current limit
threshold when USB500 mode is selected. Additionally, the precharge current is always 20% of the current
programmed by ISET, not 20% of the mode selected by EN/SET. However, if USB100 mode is selected, the
precharge current may be restricted to the USB100 limit.
Charge Done Threshold (IFULL)
The charge done threshold is programmed using the IFULL input. The user programmable charge done
threshold is set by connecting a resistor from IFULL to VSS. The value of the resistor is determined by:
R_IFULL = IFULL% x K_IFULL
(2)
The charge done threshold (IFULL%) is defined as a percentage of the fast charge current programmed at ISET.
IFULL% must be programmed between 5% and 50%. The CHG output goes high once I_BAT falls below the
threshold set by IFULL signaling to the microprocessor that the battery is fully charged and the charge cycle
should be terminated, but charging continues until disabled by the EN/SET input.
Production Test Mode (PTM)
The EN/SET interface input for the bq25040 allows the user to select the Production Test mode (PTM). In PTM,
BAT is regulated to 4.2V and supplies up to 2.3A for powering external loads with no battery installed. This
allows the user to supply loads with no battery connected as in production tests. The IC will not handle
continuous dc current of 2.3A. When using currents greater than 1.5A in PTM, the user must limit the duty cycle
at the maximum current to 20% with a maximum period of 10ms. In PTM, thermal regulation is disabled;
however, thermal shutdown is still active.
Undervoltage Lockout
The bq25040 remains in power down mode when the input voltage is below the undervoltage lockout threshold
(UVLO). During this mode, the control input (EN/SET) is ignored. The charge FET connected between IN and
BAT is off and the status outputs (CE and PG) are high impedance. Once the input voltage rises above UVLO,
the internal circuitry is turned on and the normal operating procedures are followed.
Input Overvoltage Protection
The bq25040 contains an input overvoltage protection circuit that disables the LDO output and charging when
the input voltage rises above V_OVP. This prevents damage from faulty adapters. The OVP circuitry contains a
115µs deglitch that prevents ringing on the input from line transients from tripping the OVP circuitry falsely. If an
adapter with an output greater than V_OVP is plugged in, the IC completes soft-start power up and then shuts
down if the voltage remains above V_OVP after 115µs. The LDO remains off and charging remains disabled until
the input voltage falls below V_OVP.
Input DPM Mode (V_IN-DPM)
The bq25040 uses the V_IN-DPM mode for operation from current-limited USB ports. When in USB100 or USB500
mode, V_IN-DPM is enabled, the input voltage is monitored. If V_IN falls to V_IN-DPM, the input current limit is
reduced to prevent the input voltage from falling further. This prevents the bq25040 from crashing poorly
designed or incorrectly configured USB sources. Figure 24 shows the V_IN-DPM behavior to a current limited
source. In this figure, the input source has a 250mA current limit and the device is configured with the 395mA
current limit (USB500 mode).
Copyright © 2009, Texas Instruments Incorporated
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