Datasheet

PRI
IN
V
D =
V
PH
VIN
GND
BOOT
VSENSE
COMP
TPS55010
EN
RT/CLK
SS
FAULT
C
SS
R
t
C
C
C
BOOT
T1
R
HS
R
LS
C
PRI
C
IN
INPUT
+5V
+
5V
_
1:2.5
C
O
C
Y
TPS55010
www.ti.com SLVSAV0A –APRIL 2011–REVISED JUNE 2011
Overview
The following design example illustrates how to determine the components for a single output isolated power
supply. TI offers an EVM (TPS55010EVM-009) with user guide (SLVU459) and excel calculator tool (SLVC363)
to expedite the design process. The support material is available on the TPS55010 product folder at www.ti.com.
Figure 24. 5V to 5V ISOLATED POWER SUPPLY Schematic
DESIGN GUIDE – STEP-BY-STEP DESIGN PROCEDURE
Input Voltage 5V nominal (4.5V to 5.5V)
Output Voltage 5V
Output Voltage Ripple <0.5%
Output Current 200mA
Start Voltage 4.5V
Stop Voltage 4V
PRIMARY SIDE VOLTAGE
The output voltage is a function of the primary voltage, transformer turns ratio and the diode voltage. The primary
voltage is a function of the duty cycle and input voltage, and is similar to a step down (buck) regulator as shown
in Equation 11. The primary side voltage must be lower than the minimum operating input voltage by 500 mV to
avoid maximum duty cycle problems and allow sufficient time for energy transfer during the low side power
switch on time. Typically, a primary side voltage that is 50% of the input voltage is ideal, but 20% to 80% is
acceptable. Using the design constraints, the primary side voltage could be from 3.6 V to 1.1 V. A 2.2 V primary
side voltage is selected, and the duty cycle is approximately 45%.
(11)
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