Datasheet

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DEVICE INFORMATION
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
TMR
FB
COMP
SEN
NC
SENP
V
DD
DET
CLASS
V
SS
FREQ
BL
V
BIAS
MODE
AUX
GATE
COM
RSN
RSP
RTN
TPS23750
TPS23770
SLVS590B JULY 2005 REVISED FEBRUARY 2008
Figure 2. Pinout
TERMINAL FUNCTIONS
TERMINAL
I/O DESCRIPTION
NAME NO.
Multifunction pin, serves as a converter soft start and a hiccup timer. A capacitor to RTN determines the
TMR 1 O
softstart and hiccup timing.
FB 2 I 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
COMP 3 I/O
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
SEN 4 I
SENP by the control loop when the translator is used. Typically used in a low-side switch buck converter.
NC 5 - No connect. There are no internal connections.
Voltage-level translator's positive reference voltage (sense positive) used in conjunction with SEN. Tie to the
SENP 6 I
regulated voltage positive rail when the translator is used, and V
DD
otherwise.
V
DD
7 PWR Positive supply input.
DET 8 O PoE detection pin; a 24.9 k 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
CLASS 9 O
classification.
V
SS
10 PWR 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 11 I
RTN.
RSP 12 I 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
RSN 13 I
analog return (ground). Connect to RTN.
COM 14 I Converter MOSFET gate driver circuit return. Connect to RTN.
GATE 15 O 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
AUX 16 I/O
COM.
MODE 17 I 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
V
BIAS
18 O
is required.
Converter current sense blanking selector. Leave floating for minimum blanking, tie BL to RTN for a short
BL 19 I
period, and to V
BIAS
for a long period.
FREQ 20 I 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
PowerPAD - PWR
V
SS
pin.
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