TPS5120_16 Datasheet, PDF (5/23 Pages) Texas Instruments – DUAL OUTPUT, TWO-PHASE SYNCHRONOUS BUCK DC/DC CONTROLLER

TPS5120
DUAL OUTPUT, TWOĆPHASE SYNCHRONOUS BUCK DC/DC CONTROLLER
SLVS278E – AUGUST 2000 – REVISED MARCH 2003
Terminal Functions (Continued)
TERMINAL
NAME
NO.
TRIP2
23
VCC
24
VREF5
22
5V_STBY
6
I/O
DESCRIPTION
I External resistor connection for CH2 output current control
Supply voltage input
O 5-V internal regulator output
I 5-V linear regulator control
detailed description
switching-mode power supply (SMPS) 1, 2
TPS5120 includes dual SMPS controllers that operate 180° out of phase and at the same frequency. Both
channels have standby and softstart.
5-V regulator
An internal linear voltage regulator is used for the high-side driver bootstrap voltage and source of VREF
(0.85 V). When the 5-V regulator is disconnected from the MOSFET drivers, it is only used for the source of
VREF. Since the input voltage range is from 4.5 V to 28 V, this feature offers a fixed voltage for the bootstrap
voltage so that the drive design is much easier. It is also used for powering the low-side driver. The tolerance
is 4%. The 5-V regulator is disabled when STBY1, STBY2, and 5V_STBY are all set low.
5-V switch
If the internal 5-V switch senses the 5-V input from the REG5V_IN pin, the internal 5-V linear regulator is
disconnected from the MOSFET drivers. The external 5 V is then used for both the low-side driver and the
high-side bootstrap, thus, increasing the efficiency.
error amplifier
Each channel has its own error amplifier to regulate the output voltage of the synchronous buck converter. It
is used in the PWM mode for the high output current condition (> 0.2 A). The unity gain bandwidth is 2.5 MHz.
This decreases the amplifier delay during fast load transients and contributes to a fast transient response.
skip comparator
In skip mode, each channel has its own hysteretic comparator to regulate the output voltage of the synchronous
buck converter. The hysteresis is set internally and is typically set at 9 mV. The delay from the comparator input
to the driver output is typically 1.2 µs.
low-side driver
The low-side driver is designed to drive low r_ds(on) N-channel MOSFETs. The maximum drive voltage is 5 V from
VREF5. The current rating of the driver is typically 1.5 A at source and sink.
high-side driver
The high-side driver is designed to drive low r_ds(on) N-channel MOSFETs. The current rating of the driver is 1.2 A
at source and sink. When configured as a floating driver, the bias voltage to the driver is developed from VREF5,
limiting the maximum drive voltage between OUTx_u and LLx to 5 V. The maximum voltage that can be applied
between LHx and OUTGND is 33 V.
deadtime
Deadtime prevents shoot through current from flowing through the main power FETs during switching transitions
by actively controlling the turnon time of the MOSFETs drivers.
• POST OFFICE BOX 655303 DALLAS, TEXAS 75265
5