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SLVS590B – JULY 2005 – REVISED FEBRUARY 2008
DEVICE INFORMATION
TMR
FB
COMP
SEN
NC
SENP
V
DD
DET
CLASS
V
SS
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
FREQ
BL
V
BIAS
MODE
AUX
GATE
COM
RSN
RSP
RTN
Figure 2. Pinout
TERMINAL FUNCTIONS
TERMINAL
NAME
TMR
FB
COMP
SEN
NC
SENP
V
DD
DET
CLASS
V
SS
RTN
RSP
RSN
COM
GATE
AUX
MODE
V
BIAS
BL
FREQ
PowerPAD
NO.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
-
I/O
O
I
I/O
I
-
I
PWR
O
O
PWR
I
I
I
I
O
I/O
I
O
I
I
PWR
DESCRIPTION
Multifunction pin, serves as a converter soft start and a hiccup timer. A capacitor to RTN determines the
softstart and hiccup timing.
Converter error amplifier inverting input. Tie to RTN when not used.
Converter error amplifier output and PWM block input. COMP is used for loop compensation or PWM control
with an external error amplifier and opto-isolator.
Voltage-level translator's sense input and enable; connect to RTN to disable. SEN is regulated to 1.5 V below
SENP by the control loop when the translator is used. Typically used in a low-side switch buck converter.
No connect. There are no internal connections.
Voltage-level translator's positive reference voltage (sense positive) used in conjunction with SEN. Tie to the
regulated voltage positive rail when the translator is used, and V
DD
otherwise.
Positive supply input.
PoE detection pin; a 24.9 kΩ resistor to V
DD
establishes a valid signature. It is pulled to V
SS
during detection.
Classification pin for PoE. A resistor to V
SS
sets the PoE device class. This pin is driven to 10 V during
classification.
Negative supply input from the PoE feed (after required ORing bridges).
The switched PoE negative output. RTN is the converter’s negative input rail. COM and RSN should be tied to
RTN.
Connect to the converter switching MOSFET current-sense resistor (current Sense Resistor Positive end).
Converter switching MOSFET current-sense reference (current Sense Resistor Negative end) and quiet
analog return (ground). Connect to RTN.
Converter MOSFET gate driver circuit return. Connect to RTN.
Converter switching MOSFET gate drive.
Converter gate driver supply; outputs 10 V and can accept inputs up to 16 V. Connect a bypass capacitor to
COM.
Connect to V
BIAS
to disable the error amplifier, otherwise to RTN.
Converter internal 5 V bias supply output, also used to bias external optocoupler. A bypass capacitor to RTN
is required.
Converter current sense blanking selector. Leave floating for minimum blanking, tie BL to RTN for a short
period, and to V
BIAS
for a long period.
Connect a resistor to RTN to program the switching frequency.
Internally connected to V
SS
; used to heatsink the part to the circuit board traces. Must be connected to the
V
SS
pin.
Copyright © 2005–2008, Texas Instruments Incorporated
7
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