Datasheet

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TPS72115
1.8 V 1.5 V
Boost Converter
3.3 V
1.8 V – 3 V
V
IO
V
CORE
DSP or
Controller
Two AAA
Batteries
EXTERNAL CAPACITOR REQUIREMENTS
POWER DISSIPATION AND JUNCTION TEMPERATURE
P
D(max)

T
J
max  T
A
R
JA
(1)
P
D


V
I
 V
O

 I
O
(2)
PROGRAMMING THE TPS72101 ADJUSTABLE LDO REGULATOR
V
O
 V
ref


1 
R1
R2

(3)
TPS72101 , , TPS72115
TPS72116 , TPS72118
SLVS352C – DECEMBER 2001 – REVISED MARCH 2006
APPLICATION INFORMATION (continued)
Figure 19. Dual Supply Application Circuit
A 0.1-µF ceramic bypass capacitor is required on both the input and output for stability. Larger capacitors
improve transient response, noise rejection, and ripple rejection. A higher value electrolytic input capacitor may
be necessary if large, fast rise time load transient are anticipated, and/or there is significant input resistance from
the device to the input power supply.
Specified regulator operation is assured to a junction temperature of 125°C; the maximum junction temperature
allowable without damaging the device is 150°C. This restriction limits the power dissipation the regulator can
handle in any given application. To ensure the junction temperature is within acceptable limits, calculate the
maximum allowable dissipation, P
D(max)
, and the actual dissipation, P
D
, which must be less than or equal to
P
D(max)
.
The maximum-power-dissipation limit is determined using Equation 1 :
Where:
• T
J
max is the maximum allowable junction temperature.
• R
θ JA
is the thermal resistance junction-to-ambient for the package; see the package dissipation rating table.
• T
A
is the ambient temperature.
The regulator dissipation is calculated using Equation 2 :
Power dissipation resulting from quiescent current is negligible.
The output voltage of the TPS72101 adjustable regulator is programmed using an external resistor divider as
shown in Figure 20 . The output voltage is calculated using Equation 3 :
Where:
• V
ref
= 1.225 V typ (the internal reference voltage)
8
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