TPS23750
TPS23770
www.ti.com
SLVS590A–JULY 2005–REVISED AUGUST 2005
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
FREQ
BL
V
BIAS
MODE
AUX
GATE
COM
RSN
RSP
SENP
V
DD
DET
CLASS
V
SS
RTN
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
softstart and hiccup timing.
TMR
FB
1
O
I
2
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.
COMP
3
I/O
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.
SEN
NC
4
5
6
I
-
I
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 VDD otherwise.
SENP
VDD
7
8
PWR Positive supply input.
DET
O
PoE detection pin; a 24.9 kΩ resistor to VDD establishes a valid signature. It is pulled to VSS during detection.
Classification pin for PoE. A resistor to VSS sets the PoE device class. This pin is driven to 10 V during
classification.
CLASS
VSS
9
O
10
11
12
13
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.
RTN
RSP
RSN
I
I
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
analog return (ground). Connect to RTN.
COM
14
15
I
Converter MOSFET gate driver circuit return. Connect to RTN.
Converter switching MOSFET gate drive.
GATE
O
Converter gate driver supply; outputs 10 V and can accept inputs up to 16 V. Connect a bypass capacitor to
COM.
AUX
16
17
18
I/O
I
MODE
VBIAS
Connect to VBIAS 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.
O
Converter current sense blanking selector. Leave floating for minimum blanking, tie BL to RTN for a short
period, and to VBIAS for a long period.
BL
19
20
-
I
I
FREQ
PowerPAD
Connect a resistor to RTN to program the switching frequency.
Internally connected to VSS; used to heatsink the part to the circuit board traces. Must be connected to the
VSS pin.
PWR
7
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