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TPS61010, TPS61011
TPS61012, TPS61013
TPS61014, TPS61015, TPS61016
SLVS314C – SEPTEMBER 2000 – REVISED OCTOBER 2003
DETAILED DESCRIPTION (continued)
Device Enable
The device is shut down when EN is set to GND. In this mode, the regulator stops switching, all internal control
circuitry including the low-battery comparator, is switched off, and the load is disconnected from the input (as
described above in the synchronous rectifier section). This also means that the output voltage may drop below
the input voltage during shutdown.
The device is put into operation when EN is set high. During start-up of the converter, the duty cycle is limited in
order to avoid high peak currents drawn from the battery. The limit is set internally by the current limit circuit and
is proportional to the voltage on the COMP-pin.
Under-Voltage Lockout
An under-voltage lockout function prevents the device from starting up if the supply voltage on VBAT is lower
than approximately 0.7 V. This under-voltage lockout function is implemented in order to prevent the
malfunctioning of the converter. When in operation and the battery is being discharged, the device will
automatically enter the shutdown mode if the voltage on VBAT drops below approximately 0.7 V.
Autodischarge
The autodischarge function is useful for applications where the supply voltage of a µC, µP, or memory has to be
removed during shutdown in order to ensure a defined state of the system.
The autodischarge function is enabled when the ADEN is set high, and is disabled when the ADEN is set to
GND. When the autodischarge function is enabled, the output capacitor will be discharged after the device is
shut down by setting EN to GND. The capacitors connected to the output are discharged by an integrated switch
of 300
Ω,
hence the discharge time depends on the total output capacitance. The residual voltage on VOUT is
less than 0.4 V after autodischarge.
Low-Battery Detector Circuit (LBI and LBO)
The low-battery detector circuit is typically used to supervise the battery voltage and to generate an error flag
when the battery voltage drops below a user-set threshold voltage. The function is active only when the device is
enabled. When the device is disabled, the LBO-pin is high impedance. The LBO-pin goes active low when the
voltage on the LBI-pin decreases below the set threshold voltage of 500 mV
±15
mV, which is equal to the
internal reference voltage. The battery voltage, at which the detection circuit switches, can be programmed with a
resistive divider connected to the LBI-pin. The resistive divider scales down the battery voltage to a voltage level
of 500 mV, which is then compared to the LBI threshold voltage. The LBI-pin has a built-in hysteresis of 10 mV.
See the application section for more details about the programming of the LBI-threshold.
If the low-battery detection circuit is not used, the LBI-pin should be connected to GND (or to VBAT) and the
LBO-pin can be left unconnected. Do not let the LBI-pin float.
Antiringing Switch
The device integrates a circuit that removes the ringing that typically appears on the SW-node when the
converter enters the discontinuous current mode. In this case, the current through the inductor ramps to zero and
the integrated PMOS switch turns off to prevent a reverse current from the output capacitors back to the battery.
Due to remaining energy that is stored in parasitic components of the semiconductors and the inductor, a ringing
on the SW pin is induced. The integrated antiringing switch clamps this voltage internally to V
BAT
and therefore,
dampens this ringing.
Adjustable Output Voltage
The devices with fixed output voltages are trimmed to operate with an output voltage accuracy of
±3%.
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