Texas Instruments MULTIPLE MODE SYNCHRONOUS DC/DC CONTROLLER TPS5103EVM-136 TPS5103EVM-136 데이터 시트

SLVS240A – SEPTEMBER 1999 – REVISED MAY 2001

4

POST OFFICE BOX 655303 

•

 DALLAS, TEXAS 75265

The reference voltage is used for the output voltage setting and the voltage protection(COMP). The tolerance
is 1.5% typically.

An internal linear voltage regulator is used for the high-side driver bootstrap voltage. Since the input voltage
range is from 4.5 V to 25 V, this voltage offers a fixed voltage for the bootstrap voltage so that the design for
the bootstrap is much easier. The tolerance is 6%.

The hysteretic comparator is used to regulate the output voltage of the synchronous-buck converter. The
hysteresis is set internally and is typically 9.7 mV. The total delay time from the comparator input to the driver
output is typically 400 ns for going both high and low.

The error amplifier is used to sense the output voltage of the synchronous buck converter. The negative input
of the error amplifier is connected to the VREF (1.185 V) with a resistive divider network. The output of the error
amplifier is brought out to the FB terminal to be used for loop-gain compensation.

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 1.2 A at sink current, and –1.5 A at source current.

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 sink current, and –1.7 A at source current. When configured as a floating driver, the bias voltage to the driver
is developed from VREF5, limiting the maximum drive voltage between OUT_u and LL to 5 V. The maximum
voltage that can be applied between LH and OUTGND is 30 V.

The deadtime control prevents shoot-through current from flowing through the main power FETs. During
switching transitions the 

deadtime control actively controls the turnon time of the MOSFET drivers. The typical

deadtime from the low-side-driver-off to the high-side-driver-on is 90 ns, and 110 ns from high-side-driver-off
to low-side-driver-on.

COMP is designed for use with a regulation-output monitor. COMP also functions as an internal comparator
used for any voltage protection such as the input under voltage protection. If the input voltage is lower than the
setpoint, the comparator turns off and prevents external parts from being damaged. The investing terminal of
the comparator is internally connected to REF (1.185

 V).

Current protection is achieved by sensing the high-side power MOSFET drain-to-source voltage drop during
on-time through VCC_SENSE and LL terminals. An external resistor between VREG5V_IN and TRIP, with the
an internal current source connected to the current comparator negative input, adjusts the current limit. The
typical internal current source value is 15 

µ

A in PWM mode, and 5 

µ

A in SKIP mode. When the voltage on the

positive terminal is lower than the negative terminal, the current comparator turns on the trigger, and then
activates the oscillator. This oscillator repeatedly resets the trigger until the overcurrent condition is removed.
The capacitor on the C

T 

terminal can be open or added to adjust the reset frequency.