TPS61000, TPS61001, TPS61002, TPS61003

TPS61004, TPS61005, TPS61006, TPS61007

SLVS279D – MARCH 2000 – REVISED AUGUST 2015

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9.3 Feature Description

9.3.1 Controller Circuit

The device is based on a current-mode control topology using a constant-frequency pulse-width modulator to

regulate the output voltage. It runs at an oscillator frequency of 500 kHz. The current sense is implemented by

measuring the voltage across the switch. The controller also limits the current through the power switch on a

pulse-by-pulse basis. Care must be taken that the inductor saturation current is higher than the current limit of

the TPS6100x. This prevents the inductor from going into saturation and therefore protects both device and

inductor. The current limit should not become active during normal operating conditions.

The TPS6100x is designed for high efficiency over a wide output current range. Even at light loads the efficiency

stays high because the controller enters a power-save mode, minimizing switching losses of the converter. In this

mode, the controller only switches if the output voltage trips below a set threshold voltage. It ramps up the output

voltage with one or several pulses, and again goes into the power-save mode once the output voltage exceeds

the threshold voltage. The controller enters the power-save mode when the output current drops to levels that

force the discontinuous current mode. It calculates a minimum duty cycle based on input and output voltage and

uses the calculation for the transition out of the power-save mode into continuous current mode.

The control loop must be externally compensated with an R/C/C network connected to the COMP pin. See the

application section for more details on the design of the compensation network.

9.3.2 Device Enable

The device is put into operation when EN is set high. During start-up of the converter the input current from the

battery is limited until the voltage on COMP reaches its operating point. The device is put into a shutdown mode

when EN is set to GND. In this mode, the regulator stops switching and all internal control circuitry including the

low-battery comparator is switched off. The output voltage drops to one diode drop below the input voltage in

shutdown.

9.3.3 Undervoltage Lockout

approximately 0.7 V. This undervoltage lockout function is implemented in order to prevent the malfunctioning of

the converter. When in operation and the battery is being discharged, the device automatically enters the

the device switches off and does not start up again automatically, even if the supply voltage rises above 0.9 V.

The device starts up again only after a signal change from low to high on EN or if the battery voltage is

completely removed.

9.3.4 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.

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

9.3.5 Low-EMI Switch

The device integrates a circuit which 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 Schottky diode stops conducting. Due to remaining energy that is stored in parasitic components of the

diode, inductor, and switch, a ringing on the SW pin is induced. The integrated antiringing switch clamps this

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