Datasheet

UDG-09209
VTRK1
V
IN
R2
V
OUT1
R1
R5
External
Tracking
Input
VTRK2
V
IN
R4
V
OUT2
R3
R6
POL1
POL2
0
0.6
Voltage
V
TRK1
V
TRK2
V
OUT2
V
OUT1
t – Time
UDG-09210
æ ö
æ ö æ ö
= -
ç ÷
ç ÷ ç ÷
ç ÷
è ø è ø
è ø
5 OUT2
6 OUT1
R V
1
R V
( )
æ ö
+
= ´
ç ÷
ç ÷
è ø
3 4
OUT2 REF
3
R R
V V
R
( )
æ ö
+
= ´
ç ÷
ç ÷
è ø
1 2
OUT1 REF
1
R R
V V
R
( ) ( )
( )
( )
æ ö
æ ö
ç ÷
ç ÷
ç ÷
+
æ ö
æ ö
+
+
ç ÷
è ø
´ = ´ Þ = -
ç ÷
ç ÷
ç ÷
ç ÷
ç ÷
æ ö
ç ÷
è ø
è ø
ç ÷
ç ÷
ç ÷
+
è ø
è ø
1
1 2
3 4
1 2
5
TRK1 TRK2
1 3 6
3
3 4
R
R R
R R
R R
R
V V 1
R R R
R
R R
TPS40170
SLUS970A –MARCH 2011–REVISED NOVEMBER 2013 www.ti.com
The tracking function configurations and waveforms are shown in Figure 27, Figure 29, and Figure 31
respectively.
In simultaneous voltage tracking shown in Figure 27, tracking signals, VTRK1 and VTRK2, of two modules,
POL1 and POL2, start up at the same time and their output voltages VOUT1initial and VOUT2initial are
approximately the same during initial startup. Since VTRK1 and VTRK2 are less than V
REF
(0.6 V, typ),
Equation 12 is used. As a result, components selection should meet Equation 14.
(14)
After the lower output voltage setting reaches output voltage V
OUT1
set point, where V
TRK1
increases above V
REF
,
the output voltage of the other one (V
OUT2
) continues increasing until it reaches its own set point, where V
TRK2
increases above V
REF
. At that time, Equation 13 is used. As a result, the resistor settings should meet
Equation 15 and Equation 16.
(15)
(16)
Equation 14 can be simplified into Equation 17 by replacing with Equation 15 and Equation 16
(17)
If 5-V V
OUT2
and 2.5-V V
OUT1
are required, according to Equation 15, Equation 16 and Equation 17, the selected
components can be as following:
• R
5
= R
6
= R
4
= R
2
=10 kΩ
• R
1
= 3.16 kΩ
• R
3
= 1.37 kΩ
Figure 27. Simultaneous Voltage Tracking Figure 28. Simultaneous Voltage Tracking
Schematic Waveform
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