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SI3404-A-GM

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P26
5.1 Detailed Pin Descriptions
Table 5.2. Circuit Equivalent and Description of Die Pads
Pin Name Detailed Description Circuit Detail
ISNS
Average current sense resistor input. The resistor value will set the maxi-
mum allowed current for the application. The overcurrent threshold voltage
V
ISNS_OVC
. Note that this pin voltage goes below VSS.
VSS
ISNS
FBH
High side dc-dc feedback input. Need to be tied to VPOS when not used.
See VFBREF.
VPOS
FBH
EROUT
dc-dc converter error output; current out, voltage sense. Loop compensat-
ing impedance should be connected here.
I
EROUT
= (V
FBH
– V
FBREF
) x 50 μA or
I
EROUT
= (V
FBL
– V
FBREF
) x 50 μA
VDD
EROUT
VSS
FBL
Low side dc-dc feedback input. Need to be tied to VSS when not used. See
V
FBREF
VDD
FBL
VSS
VDD
Regulated 5 V relative to VSS. There is no foldback characteristic, reaching
VDD
ILIM
the output voltage decreases.
The regulator needs C
REG
external capacitance.
VDD
VSS
Si3404 Data Sheet
Pin Descriptions
silabs.com | Building a more connected world. Rev. 1.0 | 16
Pin Name Detailed Description Circuit Detail
RCL
Classification resistor input. For class 0 this pin can be left floating. Pin is
active only at time of classification.
RCL
VNEG
R
EXT
+
I
CLASS
-
RFREQ
Used for adjusting the oscillator frequency.
The frequency is inversely proportional to the value of the connected resis-
tor.
RFREQ
R
EXT
+
I
FREQ
VPOS
-
VPOS,
VNEG
Main chip input power. Note that VNEG (the ePad on the bottom of the
chip) also provides thermal relief.
HSO
Hotswap Switch Output. The switch shorts the VNEG and HSO pins, and in-
cludes several other functions. See hotswap switch section for details.
HSO
VNEG
120V
RDET
The user has to tie the RDET resistor between this pin and VPOS. During
detection, a high voltage switch pulls down RDET to VNEG. After detection,
the reference block uses RDET as absolute chip current reference, forcing
–750 mV relative to VPOS, creating 30 µA for the internal blocks.
VPOS
RDET
VNEG
120V
120V
R
DET
Si3404 Data Sheet
Pin Descriptions
silabs.com | Building a more connected world. Rev. 1.0 | 17
Pin Name Detailed Description Circuit Detail
VT15
VT15 is input for an optional 15 V supply generated by an auxiliary trans-
former bias winding. If the bias winding voltage is lower than VT15_MIN, the
internal 15 V coarse regulator will provide the current for the 11 V regulator.
V11 is not available on the Si3404 but is included to show internal connec-
tions.
VPOS
VT15
VSS
6V
6V
6V
V11
SWO dc-dc converter switching transistor drain output, Vmax = 120 V.
SWO
VSS
VSS dc-dc converter ground.
VPOS
VSS
120V
ESD
CLAMP
Si3404 Data Sheet
Pin Descriptions
silabs.com | Building a more connected world. Rev. 1.0 | 18
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P26

SI3404-A-GM

Mfr. #:
Buy SI3404-A-GM
Manufacturer:
Silicon Labs
Description:
Power Switch ICs - POE / LAN PoE PD interface with compact footprint
Lifecycle:
New from this manufacturer.
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