TPS61000, TPS61001, TPS61002, TPS61003, TPS61004, TPS61005, TPS61006

SINGLE-CELL BOOST CONVERTER WITH START-UP INTO FULL LOAD

SLVS279A – MARCH 2000 – REVISED MAY 2000

5

POST OFFICE BOX 655303

detailed description (continued)

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 build-in hysteresis of

10 mV. Please see the application section for more details about the programming of the LBI threshold.

pin can be left unconnected. Do not let the LBI pin float.

low-EMI switch

The device integrates a circuit which removes the ringing that typically appears on the SW-node when the con-

verter enters the discontinuous current mode. In this case, the current through the inductor ramps to zero and

the Schottky diode stops conducting. Due to remaining energy that is stored in parasitic components of diode,

inductor and switch, a ringing on the SW pin is induced. The integrated anti-ringing switch clamps this voltage

voltage indicates when the diode is reverse biased. The ringing on the SW-node is damped to a large degree,

reducing the electromagnetic interference generated by the switching regulator to a very great extends.

adjustable output voltage

The accuracy of the internal voltage reference, the controller topology, and the accuracy of the external resistor

divider determine the accuracy of the adjustable output voltage version of the TPS61000. The reference voltage

has an accuracy of

±4% over line, load, and temperature. The controller switches between fixed frequency and

pulse-skip mode, depending on load current. This adds an offset to the output voltage that is equivalent to 1%

complete output current range.