Datasheet

TPS78001
GND
EN
IN OUT
V
IN
V
OUT
1 Fm
1 Fm
FB
R
1
R
2
V =V (1+)´
OUT FB
R
R
1
2
TPS780
GND
EN
V
SET
IN OUT
V
IN
V
OUT
1 Fm
1 Fm
4.2Vto5.5V 2.2Vto3.3V
On
Off
V High=V
SET OUT(LOW)
V Low=V
SET OUT(HIGH)
R
1 2
= 1 R- ´
V
V
OUT
FB
()
V =V 1+´
OUT FB
R
R
1
2
()
TI Information — Selective Disclosure
TPS780 Series
www.ti.com SBVS083D –JANUARY 2007–REVISED SEPTEMBER 2012
APPLICATION INFORMATION
Regulator
APPLICATION EXAMPLES
The output voltage of the TPS78001 adjustable
regulator is programmed using an external resistor
The TPS780 series of LDOs typically take less than
divider as shown in Figure 55. The output voltage
800μs to transition from a lower voltage of 2.2V to a
operating range is 1.2V to 5.1V, and is calculated
higher voltage of 3.3V under an output load of
using Equation 1:
150mA; see Figure 51. Additionally, the TPS780
series contain active pull-down circuitry that
automatically pulls charge out of the voltage capacitor
(1)
to transition the output voltage from the higher
voltage to the lower voltage, even with no load Where:
connected. Output voltage overshoots and
V
FB
= 1.216V typ (the internal reference voltage)
undershoots are minimal under this load condition.
Resistors R
1
and R
2
should be chosen for
The TPS780 series typically take less than 800μs to
approximately 1.2μA divider current. Lower value
transition from V
SET
low (3.3V to 2.2V), or V
SET
high
resistors can be used for improved noise
(2.2V to 3.3V); see Figure 51 and Figure 52. Both
performance, but the solution consumes more power.
output states of the TPS780 series are factory-
Higher resistor values should be avoided because
programmable between 1.5V to 4.2V. Note that
leakage current into/out of FB across R
1
/R
2
creates
during startup or steady-state conditions, it is
an offset voltage that artificially increases/decreases
important that the EN pin and V
SET
pin voltages never
the feedback voltage and thus erroneously
exceed V
IN
+ 0.3V.
decreases/increases V
OUT
. Table 3 lists several
common output voltages and resistor values. The
recommended design procedure is to choose R
2
=
1MΩ to set the divider current at 1.2μA, and then
calculate R
1
using Equation 2:
(2)
Figure 54. Typical Application Circuit
The TPS780 is also used effectively in dynamic
voltage scaling (DVS) applications. DVS applications
are required to dynamically switch between a high
operational voltage to a low standby voltage in order
to reduce power consumption. Modern multimillion
gate microprocessors fabricated with the latest sub-
micron processes save power by transitioning to a
Figure 55. TPS78001 Adjustable LDO Regulator
lower voltage to reduce leakage currents while
Programming
maintaining content. This architecture enables the
microprocessor to transition quickly into an
operational state (wake up) without requiring a reload
Table 3. Output Voltage Programming Guide
of the states from external memory, or a reboot.
OUTPUT VOLTAGE R
1
R
2
Programming the TPS78001 Adjustable LDO
1.8V 0.499MΩ 1MΩ
2.8V 1.33MΩ 1MΩ
5.0V 3.16MΩ 1MΩ
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