Datasheet

Maximum Output Current Buck
0 x Isw
D
Iout=
V
OUT
Duty Cycle Buck D =
V
IN
Maximum Output Current Boost I = x I x (1 - D)
OUT SW
h
V - V
IN
OUT
Duty Cycle Boost D =
V
OUT
TPS63036
www.ti.com SLVSB76 –AUGUST 2012
Given the average input current in figure 3 is then possible to calculate the output current reached in boost mode
using Equation 1 and Equation 2 and in buck mode using Equation 3 and Equation 4.
(1)
(2)
(3)
(4)
With,
η = Estimated converter efficiency (use the number from the efficiency curves or 0.80 as an assumption)
f = Converter switching frequency (typical 2MHz)
L = Selected inductor value
I
SW
=Minimum average input current (Figure 3)
Device Enable
The device is put into operation when EN is set high. It is put into a shutdown mode when EN is set to GND. In
shutdown mode, the regulator stops switching, all internal control circuitry is switched off, and the load is
disconnected from the input. This means that the output voltage can drop below the input voltage during
shutdown. During start-up of the converter, the duty cycle and the peak current are limited in order to avoid high
peak currents flowing from the input.
Softstart and Short Circuit Protection
After being enabled, the device starts operating. The average input current limit ramps up from an initial 400mA
following the output voltage increasing. At an output voltage of about 1.2V, the current limit is at its nominal
value. If the output voltage does not increase, the current limit will not increase. The device ramps up the output
voltage in a controlled manner even if a large capacitor is connected at the output. When the output voltage does
not increase above 1.2V, the device assumes a short circuit at the output, and keeps the current limit low to
protect itself and the application. At a short on the output during operation, the current limit also is decreased
accordingly.
Overvoltage Protection
If, for any reason, the output voltage is not fed back properly to the input of the voltage amplifier, control of the
output voltage will not work anymore. Therefore overvoltage protection is implemented to avoid the output
voltage exceeding critical values for the device and possibly for the system it is supplying. The implemented
overvoltage protection circuit monitors the output voltage internally as well. In case it reaches the overvoltage
threshold the voltage amplifier regulates the output voltage to this value.
Undervoltage Lockout
An undervoltage lockout function prevents device start-up if the supply voltage on VIN is lower than
approximately its threshold (see electrical characteristics table). When in operation, the device automatically
enters the shutdown mode if the voltage on VIN drops below the undervoltage lockout threshold. The device
automatically restarts if the input voltage recovers to the minimum operating input voltage.
Overtemperature Protection
The device has a built-in temperature sensor which monitors the internal IC temperature. If the temperature
exceeds the programmed threshold (see electrical characteristics table) the device stops operating. As soon as
the IC temperature has decreased below the programmed threshold, it starts operating again. There is a built-in
hysteresis to avoid unstable operation at IC temperatures at the overtemperature threshold.
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