TPS62000, TPS62001, TPS62002, TPS62003
TPS62004, TPS62005, TPS62006, TPS62007, TPS62008
HIGHEFFICIENCY STEPDOWN LOW POWER DCDC CONVERTER
SLVS294D SEPTEMBER 2000 REVISED MARCH 2006
5
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
operation (continued)
In the PFM mode, the converter operates with:
D Variable frequency
D Constant peak current that reduces switching losses
D Quiescent current at a minimum
Thus maintaining the highest efficiency at light load currents. In this mode, the output voltage is monitored with
the error amplifier. As soon as the output voltage falls below the nominal value, the high side switch is turned
on and the inductor current ramps up. When the inductor current reaches the peak current of typical: 150 mA
+ 50 mA/V x (VI VO), the high side switch turns off and the low side switch turns on. As the inductor current
ramps down, the low side switch is turned off before the inductor current becomes negative which completes
the cycle. When the output voltage falls below the nominal voltage again, the next cycle is started.
The converter enters the PWM mode again as soon as the output voltage can not be maintained with the typical
peak inductor current in the PFM mode.
The control loop is internally compensated reducing the amount of external components.
The switch current is internally sensed and the maximum current limit can be set to typical 600 mA by connecting
ILIM to ground or to typically 1.2 A connecting ILIM to VIN.
100% duty cycle operation
As the input voltage approaches the output voltage and the duty cycle exceeds typical 95%, the converter turns
the P-channel high side switch continuously on. In this mode, the output voltage is equal to the input voltage
minus the voltage drop across the P-channel MOSFET.
synchronization, power save mode and forced PWM mode
If no clock signal is applied, the converter operates with a typical switching frequency of 750 kHz. It is possible
to synchronize the converter to an external clock within a frequency range from 500 kHz to 1000 kHz. The device
automatically detects the rising edge of the first clock and is synchronizes immediately to the external clock.
If the clock signal is stopped, the converter automatically switches back to the internal clock and continues
operation without interruption. The switch over is initiated if no rising edge on the SYNC pin is detected for a
duration of four clock cycles. Therefore, the maximum delay time can be 8
s in case the internal clock has a
minimum frequency of 500 kHz.
In case the device is synchronized to an external clock, the power save mode is disabled and the device stays
in forced PWM mode.
Connecting the SYNC pin to the GND pin enables the power save mode. The converter operates in the PWM
mode at moderate to heavy loads and in the PFM mode during light loads maintaining high efficiency over a
wide load current range.
Connecting the SYNC pin to the VIN pin forces the converter to operate permanently in the PWM mode even
at light or no load currents. The advantage is the converter operates with a fixed switching frequency that allows
simple filtering of the switching frequency for noise sensitive applications. In this mode, the efficiency is lower
compared to the power save mode during light loads (see Figure 1).
It is possible to switch from forced PWM mode to the power save mode during operation.
The flexible configuration of the SYNC pin during operation of the device allows efficient power management
by adjusting the operation of the TPS6200x to the specific system requirements.
low noise antiringing switch
An antiringing switch is implemented in order to reduce the EMI radiated from the converter during
discontinuous conduction mode (DCM). In DCM, the inductor current ramps to zero before the end of each
switching period. The internal load comparator turns off the low side switch at that instant thus preventing the