Introduction
1
Introduction
The TPS62730 device is a high-frequency synchronous stepdown dc-dc converter optimized for
ultralow-power wireless applications. The device is optimized to supply TI
’
s low-power wireless sub-1-GHz
and 2.4-GHz RF transceivers. The TPS62730 reduces the current consumption drawn from the battery
during TX and RX modes by a highly efficient stepdown voltage conversion. It provides up to 100-mA
output current and allows the use of tiny and low-cost chip inductors and capacitors. This device supports
most Li-ion primary battery chemistries, with an input range of 1.9 V to 3.9 V dc.
The TPS62730 features an ultralow-power bypass mode with a typical 30 nA current consumption to
support low-power modes of modern RF transceivers. In this bypass mode, the input is connected the
VOUT pin via an internal 2-
Ω
bypass FET.
The device automatically enters bypass mode when the input (battery) voltage falls to the bypass
transition threshold.
2
Considerations With Evaluating the TPS62730
This part has two modes of operation, the switching buck mode and the dc bypass mode. The IC
automatically shuts down the switcher once the input voltage drops to the bypass threshold, which is a few
millivolts above the regulation voltage, saving on bias power to the switcher.
Bypass mode can be implemented at higher input voltages by pulling the ON/BYP pin low. There may be
some applications where the input voltage is too high for the system, and caution should be taken that this
mode transfer is not performed for these cases. The ON/BYP pin should not be floated (open), or it is
highly likely that the IC will be in an unknown state/mode and the output voltage could be anywhere
between the input voltage and the regulation voltage.
The EVM has a pullup resistor on the ON/BYP pin to Vin so that it stays in the switching mode if the
jumper is removed and only goes into the bypass mode if the shunt is moved to ground the ON/BYP pin.
This pullup resistor on the EVM causes the input to be loaded, when in bypass mode, by Vin/1 M
Ω
. In a
typical application, a driver controls the ON/BYP pin and does not load the input; thus, this current should
not be considered in the quiescent current when in bypass mode.
The pullup resistor for the status output on the EVM should also be considered (ignored) when calculating
the efficiency of the converter. The EVM uses a stiff pullup, because it is not known what will be
connected to the STAT pin, but when designing the system a much higher-value resistor may be
appropriate.
3
Performance Specification Summary
Specification
Test Conditions
MIN
TYP
MAX
UNIT
Input dc voltage, Vin
Recommended input voltage range
1.9
3.9
V
Reduced performance, Vin
(1)
Input voltage too low to maintain output regulation
1.9
2.1
V
(1)
As the output load increases from 0 mA to 100 mA, the input voltage should be
>
2.2 V to avoid dropout and maintain regulation.
4
Test Summary
The TPS62730EVM-726 board requires an adjustable 5-V,
≥
150-mA current-limited power source to
provide input power and a resistive load between 100
Ω
and 21
Ω
. The test setup connections and
jumper-setting selections are configured for a stand-alone evaluation, but can be changed to interface with
external hardware such as a system load and microcontroller.
2
TPS62730 Stepdown Converter With Bypass Mode for Ultralow-Power Wireless
SLVU455
–
April 2011
Applications
Copyright
©
2011, Texas Instruments Incorporated
