TPS61000, TPS61001, TPS61002, TPS61003, TPS61004, TPS61005, TPS61006, TPS61007
SINGLE- AND DUAL-CELL BOOST CONVERTER WITH START-UP INTO FULL LOAD
SLVS279C – MARCH 2000 – REVISED APRIL 2003
4
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
functional block diagram (continued)
adjustable output-voltage option (TPS61007 only)
VREF
VBAT
Control Logic
Oscillator
Gate Drive
UVLO
Current Sense
Current Limit
Slope Compensation
Bandgap
Reference
EN
LBI
LBO
GND
COMP
L1
D1
VOUT
CO
CI
SW
Comparator
LBI/LBO
Comparator
Error
Amplifier
Antiringing
Comparator
and Switch
FB
FBGND
detailed description
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.
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.