Datasheet
Table Of Contents
V
C
T2P From
TPS2379
R
T2P
R
T2P-OUT
V
OUT
VT2P -OUT
VT2P Low
Indicates
Type 2
I
T2P-OUT
I
T2P
OUT T2P OUT
T2P OUT
T2P OUT
V V
5 0.4
I 0.46mA
R 10000
-
-
-
-
-
= = =
T2P-OUT
T2P-MIN T2P
C T2P FWLED
T2P
T2P
I
0.46mA
I 0.46mA, Select I 1mA
CTR 1.00
V V V
12 V 0.26 V 1.1 V
R 10.6kΩ
I 1mA
= = = =
- -
- -
= = =
.
TPS2379
www.ti.com
SLVSB98 –MARCH 2012
T2P Pin Interface
The T2P pin is an active-low, open-drain output which indicates that a high power source is available. An
optocoupler can interface the T2P pin to circuitry on the secondary side of the converter. A high-gain optocoupler
and a high-impedance (e.g., CMOS) receiver are recommended. Design of the T2P optocoupler interface can be
accomplished as follows:
Figure 27. T2P Interface
1. As shown in Figure 27, let V
C
= 12 V, V
OUT
= 5 V, R
T2P-OUT
= 10 kΩ, V
T2P
= 260 mV, V
T2P-OUT
= 400 mV.
spacer
(2)
2. The optocoupler current transfer ratio, CTR, will be needed to determine R
T2P
. A device with a minimum CTR
of 100% at 1 mA LED bias current, I
T2P
, is selected. Note that in practice, CTR will vary with temperature,
LED bias current and aging. These variations may require some iteration using the CTR-versus- I
DIODE
curve
on the optocoupler data sheet.
(a) The approximate forward voltage of the optocoupler diode, V
FWLED
, is 1.1 V from the data sheet.
(b)
MM
(c) Select a 10.7 kΩ resistor.
THERMAL CONSIDERATIONS AND OTSD
Sources of nearby local PCB heating should be considered during the thermal design. Typical calculations
assume that the TPS2379 is the only heat source contributing to the PCB temperature rise. It is possible for a
normally operating TPS2379 device to experience an OTSD event if it is excessively heated by a nearby device.
ESD
ESD requirements for a unit that incorporates the TPS2379 have a much broader scope and operational
implications than are used in TI’s testing. Unit-level requirements should not be confused with reference design
testing that only validates the ruggedness of the TPS2379.
Copyright © 2012, Texas Instruments Incorporated Submit Documentation Feedback 21
Product Folder Link(s) :TPS2379