ZHCSHL4I October 2008 – December 2017 TPS23754 , TPS23754-1 , TPS23756
PRODUCTION DATA.
PIN | TYPE | DESCRIPTION | ||
---|---|---|---|---|
NAME | TPS23754
and TPS23756 |
TPS23754-1 | ||
APD | 17 | 17 | I | Raising VAPD – VARTN above 1.5 V disables the internal hotswap switch, turns class off, and forces T2P active. This forces power to come from a external VDD1-RTN adapter. Tie APD to ARTN when not used. |
ARTN | 8 | 8 | — | ARTN is the DC-DC converter analog return. Tie to RTN and COM on the circuit board. |
BLNK | 18 | 18 | I | Connect to ARTN to use the internally set current-sense blanking period, or connect a resistor from BLNK to ARTN to program a more accurate period. |
CLS | 15 | 15 | I | Connect a resistor from CLS to VSS to program classification current. 2.5 V is applied to the program resistor during classification to set class current. |
COM | 4 | 4 | — | Gate driver return, connect to ARTN and RTN. |
CS | 3 | 3 | I/O | DC-DC converter switching MOSFET current sense input. See RCS in Figure 27. |
CTL | 1 | 1 | I | The control loop input to the pulse-width modulator (PWM), typically driven by output regulation feedback (for example, optocoupler). Use VB as a pullup for CTL. |
DEN | 13 | 13 | I/O | Connect a 24.9-kΩ resistor from DEN to VDD to provide the PoE detection signature. Pulling this pin to VSS during powered operation causes the internal hotswap MOSFET to turn off. |
DT | 16 | 16 | I | Connect a resistor from DT to ARTN to set the GATE to GAT2 dead time. Tie DT to VB to disable GAT2 operation. |
FRS | 19 | 19 | I | Connect a resistor from FRS to ARTN to program the converter switching frequency. FRS may be used to synchronize the converter to an external timing source. |
GATE | 5 | 5 | O | Gate drive output for the main DC-DC converter switching MOSFET. |
GAT2 | 7 | 7 | O | Gate drive output for a second DC-DC converter switching MOSFET (see Figure 27). |
NC | — | 14 | — | Float this no-connect pin. |
PAD | — | — | — | Connect to VSS. |
PPD | 14 | — | I | Raising VPPD-VSS above 1.55 V enables the hotswap MOSFET and activates T2P. Connecting PPD to VDD enables classification when APD is active. Tie PPD to VSS or float when not used. |
RTN | 9 | 9 | — | RTN is the output of the PoE hotswap MOSFET. |
T2P | 20 | 20 | O | Active low output that indicates a PSE has performed the IEEE 802.3at type 2 hardware classification, PPD is active, or APD is active. |
VB | 2 | 2 | O | 5.1-V bias rail for DC-DC control circuits and the feedback optocoupler. Typically bypass with a 0.1 μF to ARTN. |
VC | 6 | 6 | I/O | DC-DC converter bias voltage. Connect a 0.47 μF (minimum) ceramic capacitor to ARTN at the pin, and a larger capacitor to power start-up. |
VDD | 12 | 12 | I | Connect to the positive PoE input power rail. VDD powers the PoE interface circuits. Bypass with a 0.1-μF capacitor and protect with a TVS. |
VDD1 | 11 | 11 | I | Source of DC-DC converter start-up current. Connect to VDD for many applications. |
VSS | 10 | 10 | — | Connect to the negative power rail derived from the PoE source. |