TPS2370DR

 www.ti.com SLUS537C − AUGUST 2002 − REVISED MARCH 2004     
 
     
 
        FEATURES DESCRIPTION D Integrated Power Interface Switch for IEEE Acting as an interface between the power sourcing equipment (PSE) and the powered device (PD), the TPS2370 performs all detection, classification, inrush current limiting, and switch FET control that is necessary for compliance with the IEEE 802.3af Standard. An internal 0.3-Ω FET provides maximum power delivery. As an additional feature, the TPS2370 interfaces with the enable/soft-start signal of a dc-to-dc converter, eliminating the need to have an accurate UVLO in the dc-to-dc converter. 802.3af Powered Devices (PDs) D Provides PD Detection Signature D Provides PD Classification Signature (Class 0−4) D Programmable Inrush Current Limit D Internal 0.3-Ω Low-Side FET D Interfaces to DC/DC Soft-Start for DC/DC Enable D Internal Thermal Protection – Disconnects PD Load D Minimal External Parts Count D 8-Pin SOIC, 8-Pin TSSOP Packages APPLICATIONS D D D D VoIP Phones Internet Appliances At low input voltages (1.8 V to 10 V), the TPS2370 draws less than 12 µA, allowing accurate sensing of the external 24.9-kΩ discovery resistor. At input voltages between 15 V and 20 V, an external resistor sets the level of current to be drawn during classification mode. TPS2370 is compatible with current as well as voltage measurement schemes for classification. Above 20-V input, the classification current is shut off, reducing internal power dissipation. The TPS2370 drives an internal low-side FET for control of the return side of the power path. The internal FET is turned on when the input voltage reaches 40 V and above. When the input voltage decreases, the FET remains on until the input voltage drops to below 30 V. Wireless LAN Access Points Bluetooth Access Points TYPICAL APPLICATION V+ 24.9 k
8 3 44 V TO 57 V SMAJ54A 0.1 f CDCDCIN TPS2370 RLIM 1 6 RCLASS CSS 2 4 V− DC/DC Converter/ Controller VREG Ethernet Appliance 5 UDG−03057 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. PowerPAD is a trademark of Texas Instruments. Bluetooth is a trademark of Bluetooth SIC, Inc. 
 
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 www.ti.com SLUS537C − AUGUST 2002 − REVISED MARCH 2004 DESCRIPTION (CONTINUED) During initial turnon of the switch (inrush mode), an external resistor is used to program the inrush current, allowing a wide range of capacitor values to be used at the load. According to IEEE 802.3af specification, inrush current of 400 mA is allowed only for 50 ms, limiting the load capacitor to approximately 180 µF. A programmable inrush current limit removes this limitation, allowing a larger capacitor to be used with a lower inrush current limit. These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. ORDERING INFORMATION PACKAGE(1) PART NUMBER Plastic TSSOP (PW) TPS2370PW Plastic SOIC (D) TPS2370D TA 0°C to 70°C (1) The PW and D packages are also available taped and reeled. Add an R suffix to the device type (i.e., TPS2370PWR). ABSOLUTE MAXIMUM RATINGS Over operating free-air temperature range unless otherwise noted (2) TPS2370 Input voltage range, wrt VEE ILIM 4 CLASS 12 DET, RTN, EN_DC, VDD 68 EN_DC (wrt RTN) 5 UNIT V Operating junction temperature range, TJ −55 to 150 °C Storage temperature, Tstg −65 to 150 °C Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds 300 °C (2) Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. RECOMMENDED OPERATING CONDITIONS MIN Input voltage, VI Operating junction temperature, TJ 0 NOM MAX UNIT 48 57 V 70 °C DISSIPATION RATINGS(3)(4) TA < 25°C POWER RATING TA = 25°C DERATING FACTOR TA = 70°C POWER RATING 258.5°C/W 464 mW 3.9 mW/°C 290 mW 176.0°C/W 682 mW 5.7 mW/°C 426 mW PACKAGE THERMAL IMPEDANCE JUNCTION-TO-AMBIENT 8-Pin Plastic TSSOP (PW) 8-Pin Plastic SOIC (D) (3) Test board conditions: 1. 3” x 3”, 4 layers, thickness: 0.062” 2. 1.5 oz. copper traces located on the top of the PCB 3. 1.5 oz. copper ground plane on the bottom of the PCB 4. 0.5 oz. copper ground planes on the 2 internal layers 5. 12 thermal vias (4) Maximum power dissipation may be limited by overcurrent protection. 2 
 www.ti.com SLUS537C − AUGUST 2002 − REVISED MARCH 2004 ELECTRICAL CHARACTERISTICS VDD = 48 V; TA = 0°C to 70°C; all voltages and currents are with respect to VEE; (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX 5 12 73 76 UNIT SUPPLY Offset current VDD = 1.8 V, DET = OPEN IDD Sleep current 1.8 V ≤ VDD < 10 V, DET = OPEN IDET Detection load current RDET = 24.9 kΩ, VDD = 1.8 V RDET = 24.9 kΩ, VDD = 9.5 V 380 390 400 Turn on 10.0 12.5 14.0 Turn off 21.5 22.5 23.5 2.2 2.5 2.8 Classification current threshold 3 70 VDD current class 0 0.44 W ≤ PPoE ≤ 12.95 W, 15 V ≤ VDD ≤ 20 V, RCLASS = 4.42 kΩ VDD current class 1 0.44 W ≤ PPoE ≤ 3.84 W, 15 V ≤ VDD ≤ 20 V, RCLASS = 953 Ω 10.4 10.8 11.5 VDD current class 2 3.84 W ≤ PPoE ≤ 6.49 W, 15 V ≤ VDD ≤ 20 V, RCLASS = 549 Ω 18.1 18.6 19.5 VDD current class 3 6.49 W ≤ PPoE ≤ 12.95 W, 15 V ≤ VDD ≤ 20 V, RCLASS = 357 Ω 27.7 28.4 29.9 VDD current class 4 Reserved for future use, 15 V ≤ VDD ≤ 20 V, RCLASS = 255 Ω 38.5 39.6 42.0 30 V ≤ VDD ≤ 57 V, RCLASS = 255 Ω Turn on 500 800 38.6 40.2 41.8 Turn off VDD quiescent current Input UVLO threshold 30.2 31.4 32.6 UVLO hysteresis 7.8 8.8 9.8 EN_DC sink current 40 80 200 RTN threshold for EN_DC µA A V mA µA V µA 1.2 1.5 1.8 V 0.15 0.30 0.60 Ω Full load current limit IRTN = 200 mA VRTN < 1.5 V 405 455 505 ILIM current limit programming RLIM = 125 kΩ, VRTN > 1.5 V during startup 180 250 300 DMOS RDS(on) Thermal shutdown temperature 144 Thermal shutdown hysteresis 20 mA °C D OR PW PACKAGE (TOP VIEW) ILIM CLASS DET VEE 1 8 2 7 3 6 4 5 VDD NC EN_DC RTN 3 
 www.ti.com SLUS537C − AUGUST 2002 − REVISED MARCH 2004 TERMINAL FUNCTIONS TERMINAL NAME NO. I/O DESCRIPTION CLASS 2 O Sets classification level with a single resistor to VEE. A precision voltage of 10 V is applied to this pin during classification. RCLASS values listed in Table 1. DET 3 O Connect the 24.9-kΩ detection resistor (RDET) between this pin and VDD. EN_DC 6 O Ties to dc-to-dc converter’s shutdown or soft-start pin. Sinks 80 µA until the load capacitor is fully charged. ILIM 1 O Sets start-up current limit level with a resistor to VEE. If using CDC2DCIN > 180 µF, IRUSH must be less than 400 mA. Extra capacitance on ILIM pin can cause oscillations in the current waveform. RTN 5 O Return pin. Connect this pin to input return side of the dc-to-dc converter. VDD 8 I Connection to PD input port positive voltage. VEE 4 I Input side power return for the controller. ǒ Ǔ 25 kW (1) I INRUSH + 450 mA * RLIM (1 A) DETAILED PIN DESCRIPTIONS ILIM (Pin 1) Inrush current limiting pin. This pin is used to program the inrush current of the device. By placing a resistor to VEE from this pin, the inrush current into the load is limited via the following equation: ǒ Ǔ I INRUSH + 450 mA * 25 kW R LIM (1 A) (1) CLASS (Pin 2) Classification pin. The PD can be optionally classified by adding a resistor from this pin to ground. The resistor specific to each class is given in Table 1: PoE Classification Resistance Values. DET (Pin3) Detection pin. This pin is used to set up the detection resistance during PD detection. By tying a resistor, RDET, from this pin to VDD, the user sets the detection resistance. It should be noted that the device itself looks like approximately 1 MΩ of resistance in parallel with RDET. VEE (Pin 4) Negative supply to the device. RET (Pin 5) Negative supply to the load. This pin is the drain side of a FET between the RET pin and the VEE pin, providing hot swap capabilities to the load. When the FET is switched on, there is approximately 300 mΩ between this pin and VEE. EN_DC (Pin 6) Enable pin for the load. This pin is intended to be used with a dc-to-dc coverter with a soft start capacitor. When power is not available to the dc-to-dc converter, this pin sinks 80 µA and holds off the soft-start capacitor on the dc-to-dc converter. Once the voltage across the load is within 1.5 V of its final value, the EN_DC pin stops drawing current and becomes high impedance, allowing the dc-to-dc converter to soft start normally. VDD (Pin 8) Positive supply to the device. 4 
 www.ti.com SLUS537C − AUGUST 2002 − REVISED MARCH 2004 Table 1. PoE Classification Resistance Values POWERED DEVICES (PDs) Power (W) CLASSIFICATION CURRENT (mA) 0 RESISTANCE (RCLASS) VALUE (Ω) 4420 0.44 − 12.95 2.5 1 953 0.44 − 3.84 10.8 2 549 3.84 − 6.49 18.6 3 357 6.49 − 12.95 28.4 4 255 reserved for future use 39.6 CLASS INTERNAL BLOCK DIAGRAM TO DC/DC’s Positive Input +VE SUPPLY VDD RDET 24.9 kΩ 8 UVLO, Detection, Classification Control CLASS 2 LDO 10 V Precision Bandgap Reference Precision Current Source DET 3 Internal Supplies SMAJ54A 0.1 f N/C 7 5V 80 µA 15 V EN_DC 6 1.5 V RCLASS RTN 20 µA ILIM 1 5 + 2 kΩ TO DC/DC’s INPUT RETURN 0.1 Ω 4 RLIM −VE SUPPLY VEE UDG−02102 5 
 www.ti.com SLUS537C − AUGUST 2002 − REVISED MARCH 2004 STATE DIAGRAM DETECTION VDD < 10 V IDD = VDD/(RDET) || 1 MΩ Switch Resistance > 100 MΩ CLASSIFICATION Power Down 10 V < VDD < 22 V IDD ≅ 10 V/(RCLASS) Switch Resistance > 100 MΩ INRUSH MODE VDD > 40 V (rising edge) VRTN > 1.5 V IRET = IINRUSH = 450 mA − (25 kΩ/RLIM) x (1 A) Switch Resistance ≈ 100 Ω LATCH OFF VDD > 30 V IDD < 1 mA Switch Resistance  100 MΩ NORMAL OPERATION VDD > 30 V (IRET = ILOAD) < 450 mA Switch Resistance ≈ 0.3 Ω NO YES TSD Count < 7? OVERLOAD/FAULT VDD > 30 V IRET = 450 mA Switch Resistance ≈ 100 Ω YES TJ < 145 _C? THERMAL SHUTDOWN VDD > 30 V IDD < 1 mA Switch Resistance > 100 MΩ NO MACHINE STATE 0 6 Detection (RLOAD = 25 kΩ) Classification 2 15 4 6 8 10 20 25 UVLO OFF (Falling Edge) UVLO ON (Rising Edge) 31 40 Normal Operation (IDD = 450 mA) 44 50 57 
 www.ti.com SLUS537C − AUGUST 2002 − REVISED MARCH 2004 APPLICATION INFORMATION OVERVIEW With the addition of power via media-dependent interface (MDI) to the IEEE 802.3af Standard, all data terminal equipment (DTE) now has the option to receive power over existing cabling that is used for data transmission. The IEEE 802.3af Standard defines the requirements associated with providing and receiving power over the existing cabling. The power sourcing equipment (PSE) provides the power on the cable and the powered device (PD) receives the power. As part of the IEEE 802.3af Standard, the interface between the PSE and PD is defined as it relates to the detection and classification protocol. POWER SOURCING EQUIPMENT DETECTION OF A POWERED DEVICE A powered device (PD) draws power or requests power by participating in a PD detection algorithm. This algorithm requires the power sourcing equipment (PSE) to probe the link looking for a valid PD. The PSE probes the link by sending out a voltage between 2.8 V and 10 V across the power lines. A valid PD detects this voltage and places a resistance of between 23.75 kΩ and 26.25 kΩ across the power lines. Naturally, the current varies depending on the input voltage. On detecting this current, the PSE concludes that a valid PD is connected at the end of the ethernet cable and is requesting power. If the powered device (PD) is in a state in which it does not accept power, the PD is required to place a resistance above or below the values listed for a valid PD. On the lower end, a range between 12 kΩ and 23.75 kΩ signifies that the PD does not require power. On the higher end, the range is defined to be between 26.25 kΩ and 45 kΩ . Any resistance value less than 12 kΩ and greater than 45 kΩ, is interpreted by the PSE as a nonvalid PD detection signature. The TPS2370 participates in the detection algorithm by activating an internal FET, which connects the DET pin of the device to VEE. As a result, any resistance connected between VDD and the DET pin of the TPS2370 is, in effect, across the power lines. This internal FET is active only when input power to the PD is between 2.8 V and 10 V. POWER SOURCING EQUIPMENT CLASSIFICATION OF A POWERED DEVICE After the detection phase, the PSE can optionally initiate a classification of the PD. The classification of a PD is used by the PSE to determine the maximum power required by the PD during normal operation. Five different levels of classification are defined by the IEEE 802.3af Standard. These levels are shown in Table 2. Table 2. Powered Device Classification Levels CLASS USAGE POWER DEVICE POWER (W) MIN MAX MIN MAX 0 Default 0.44 12.95 0 4 1 Optional 0.44 3.84 9 12 2 Optional 3.84 6.49 17 20 3 Optional 6.49 12.95 26 30 4 Not allowed 36 44 reserved for future use CLASSIFICATION CURRENT (mA) Classification of the PD is optionally performed by the PSE only after a valid PD has been detected. To determine PD classification, the PSE increases the voltage across the power lines to between 15.5 V and 20.5 V. The amount of current drawn by the PD determines the classification (see Table 2). When the input voltage to the TPS2370 is between 14.0 V and 20.5 V, the TPS2370 uses an internal regulator to generate a fixed voltage on the CLASS pin. A resistor connected between the CLASS pin and VEE draws a fixed amount of current and thereby defines the classification level of the PD. 7 
 www.ti.com SLUS537C − AUGUST 2002 − REVISED MARCH 2004 APPLICATION INFORMATION POWER SOURCING EQUIPMENT POWER TO THE POWERED DEVICE On completion of the detection and optional classification phases, the PSE ramps its output voltage above 42 V . Once the UVLO threshold has been reached, the internal FET is turned on. At this point, the PD begins to operate normally and it continues to operate normally as long as the input voltage remains above 30 V. For most PDs, this input voltage is down-converted using an onboard dc-to-dc converter to generate the required voltages. The TPS2370 is designed to apply the PSE output voltage of 36 V to 57 V across the input of the onboard dc-to-dc converter. This is accomplished on the TPS2370 by turning on an internal pass FET located across the power return. PROGRAMMING THE INRUSH CURRENT During the initial turnon of the pass FET, an inrush current is created from the charging of the capacitance at the input of the dc-to-dc converter. According to the IEEE 802.3af specification, if the input capacitance is less than 180 µF, the PSE limits the inrush current. If the input capacitance is greater than 180 µF, the IEEE 802.3af specification requires the PD to limit the inrush current to less than 400 mA. In order to satisfy the IEEE 802.3af requirements, the TPS2370 has been designed for a typical current limit of 450 mA. This current limit setting satisfies the normal operation requirements as well as the inrush requirements for a capacitive load of 180 µF or less. If a larger load capacitor is desired, the TPS2370 has been designed with a programmable inrush current limit feature. This feature allows the designer the option of using a capacitor larger than 180 µF. Note that the inrush current feature may also be used to lower voltage drops in the cabling between the PSE and the PD during start-up. The programmable inrush current limit has a range of 50 mA to 449 mA. The limit is set by connecting an external resistor from ILIM (pin 1) to VEE (pin 4) of the TPS2370. Equation (1) shows the calculation for the programmable inrush current limit. ǒ Ǔ I INRUSH + 450 mA * 25 kW R LIM (1 A) (2) where RLIM is a value between 63.5 kΩ and 25 MΩ. USING EN_DC AS A SOFT-START OR A POWER-GOOD FUNCTION The EN_DC pin is an output intended for use as a soft-start for a dc-to-dc converter. During the initial turnon of the pass FET, an internal 80-µA current sink is enabled on the EN_DC pin. This internal current sink is removed only after the load capacitance has been charged to within 1.5-V of the supply voltage. By connecting the EN_DC output to the soft-start capacitor of a dc-to-dc converter, the internal current sink keeps the dc-to-dc converter off during start-up. Once the voltage across the converter has reached within 1.5 V of full voltage, the dc-to-dc converter is allowed to soft start. For operation as a power-good output, the EN_DC requires an external pull-up resistor. A 1-MΩ resistor is recommended. The EN_DC output also requires a clamp to limit the output voltage to within recommended operating levels. A 5-V zener diode connected between EN_DC and RTN (pin 5 of the TPS2370) is recommended. This configuration allows the EN_DC pin to act as an open-drain output with which many designers are more familiar. 8 
 www.ti.com SLUS537C − AUGUST 2002 − REVISED MARCH 2004 APPLICATION INFORMATION SURGE SUPPRESSION As specified in the Absolute Maximum Ratings table, the absolute maximum input voltage of the TPS2370 is 68 V. The IEEE 802.3af Power-over-Ethernet Standard specifies the voltage range of PSE output as between 44 V and 57 V. This PSE output voltage range would be reduced by cable, connector, and other IR drops between the PSE and the TPS2370 in the PD. However, the use of extended cable lengths and transformers in some applications may induce transients in excess of 68 V during a hot plug event. To manage these transient events and keep them from significantly exceeding the application’s maximum voltage, a transorb such as the SMAJ54A should be placed between the positive input supply, VDD (pin 8), and the negative input supply, VEE (pin 4). This, combined with a 0.1-µF bypass capacitor in parallel with the transorb, helps to protect the TPS2370 from damage caused by transients during hot plug events. The transorb or zener diode should be selected such that it does not zener below the maximum required application voltage of 57 V, but before reaching the 68-V absolute maximum rating. For layout purposes, the 0.1-µF capacitor should be placed as close as possible to the device; the transorb or zener diode should be placed as close to the supply connector as possible. Based on the nature of the PD application, these measures should be considered an implementation requirement. USE OF BARREL RECTIFIERS Many applications use barrel rectifiers after the RJ-45 connector in order to be polarity insensitive. Barrel rectifiers in front of the TPS2370 cause the voltages at the device to be lower than the voltages at the RJ-45. The TPS2370 allows for this and is IEEE802.3af compliant during the detection and classification phases. For the detection phase, the device begins detection for voltages as low as 1.3 V across the supply pins. For the optional classification phase, the device is guaranteed to start classification below 14 V across the supply pins. Once classification has been engaged, it becomes latched-in and further voltage drops due to cable resistance and class current does not cause it to switch out of classification. Thus, the TPS2370 allows for at least a 1.5-V drop between the RJ-45 and the TPS2370 due to barrel rectifiers during both detection and classification phases. However, in cases where the PSE is operating at the minimum class voltage (15.5 V) and there is a 20-Ω, 100-m cable between the PSE and the PD, class 3 devices may not classify correctly when using barrel rectifiers. Class 3 device designs should include Schottky diodes to handle all corner cases, or switch to class 0 devices when using barrel rectifiers. THERMAL SHUTDOWN In the event of a short circuit or overload condition, the TPS2370 begins to heat up until thermal shutdown is reached. Once thermal shutdown is reached, the internal FET is switched off, removing the load from the supply. After the device has cooled sufficiently, it retries by restarting the internal FET. If the overload or short is not removed, the device cycles thermal shutdown seven times before latching the internal FET off. Once the internal FET is latched off, power needs to be cycled to reset the latch. 9 
 www.ti.com SLUS537C − AUGUST 2002 − REVISED MARCH 2004 APPLICATION INFORMATION Figure 1 shows an application where 40 V < VIN < 57 V. In this case, the brick supply is greater then 40 V and goes through TPS2370. PoE POWERED DEVICE FRONT END RJ−45 3 V+ RX RDET 6 1 8 CDCDCIN 3 RLIM 1 TX TPS2370 2 2 VREG ETHERNET DEVICE CSS 4 S P A R E DC/DC CONVERTER 6 RCLASS 5 7 V− 4 5 8 DC BRICK SUPPLY Figure 1. For Applications 40 V < VIN < 57 V. Figure 2 shows an application where VIN < 40 V. In this application, the brick supply is bypassing the switch. Consequently, the dc-to-dc converter can operate from any voltage. However, for VBRICK < 23 V, a class 0 resistor (RCLASS = 4.42 kΩ) is recommended. This minimizes the power dissipation in TPS2370 if VBRICK falls in the classification voltage range (15 V to 20 V). The 80-µA current sink on EN_DC pin is enabled only if VDD > 40 V. PoE POWERED DEVICE FRONT END RJ−45 3 V+ RX RDET 6 1 8 CDCDCIN 3 RLIM 1 TX TPS2370 2 2 DC/DC CONVERTER 6 4 S P A R E RCLASS 5 7 8 V− CSS 4 5 DC BRICK SUPPLY Figure 2. For Applications VIN < 40 V. 10 VREG ETHERNET DEVICE PACKAGE OPTION ADDENDUM www.ti.com 10-Dec-2020 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan (2) Lead finish/ Ball material MSL Peak Temp Op Temp (°C) Device Marking (3) (4/5) (6) TPS2370PW NRND TSSOP PW 8 150 RoHS & Green NIPDAU Level-1-260C-UNLIM 0 to 70 2370 TPS2370PWR NRND TSSOP PW 8 2000 RoHS & Green NIPDAU Level-1-260C-UNLIM 0 to 70 2370 (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of