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NWK914D
NWK914D
PHY/PMD High Speed Copper Media Transceiver Preliminary Information
DS4829 - 1.1 December 1997
The NWK914D is a Physical Layer device designed for use in 100BASE-TX applications. The NWK914D has integrated the 100mb/s transceiver, clock and data recovery and NRZI conversion circuitry. It is designed for use in cost effective NIC adapter cards and 100BASE-TX repeater and switch applications. The device connects through a 5 bit symbol interface directly with any MAC controller that includes the PCS layer, resulting in a simple and cost effective solution. It will also interface with a PCS device such as the NWK935 to form a complete 100BASE-TX Physical Layer for connection to the IEEE 802.3 standard MII interface.
RDAT4 RDAT3 RDAT2 RDAT1 RDAT0 TXC TTLVCC REFCLK TDAT0 TDAT1 TDAT2 TDAT3
52 51 50 49 48 47 46 45 44 43 42 41 40
TDAT4
TTLGND N/C N/C RXC SDT RDLV CC N/C N/C RXPLLGND LFRB LFRA RXPLLV CC RXVCC
FEATURES s Compatible with IEEE-802.3 Standards s Operates over 100 Meters of STP and Category 5 UTP cable s Five Bit TTL Level Symbol Interface s Integrated Clock and Data Recovery s Supports Full-duplex Operation s Integral 10 Mb/s Buffer for Dual 10 Mb/s & 100 Mb/s Applications s Adaptive Equalization s 25MHz to 125MHz Transmit Clock Multiplier s Programmable TX Output Current s Base Line Wander Correction
1 2 3 4 5 6 7 8 9 10 11 12 13
39 38 37 36 35 34 33 32 31 30 29 28 27
TTLGND TEST TESTIP N10/100 LBEN TDLV CC TXOE TXPLLV CC LFTA LFTB TXPLLGND BGAPGND SUBGND
RXGND RXIP RXIN RXVCC 1 EQSEL 10TXIN 10TXIP TXVCC TXON TXOP TXGND TXREF BGAPVCC
14 15 16 17 18 19 20 21 22 23 24 25 26
GP52
Fig.1 Pin connections - top view
s Single +5V supply s 52 Pin PQFP package ORDERING INFORMATION NWK914D/CG/GP1N
MAC or Repeater Controller IC
MII Interface
Symbol Interface
NWK935 100 PCS
NWK914D
Isolation Magnetics
RJ-45
Fig.2 Simplified system diagram
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NWK914D
ABSOLUTE MAXIMUM RATINGS
Operation at absolute maximum ratings is not implied. Exposure to stresses outside those listed could cause permanent damage to the device. DC Supply voltage (VCC) Storage temperature (tst) ESD -0.5 to +7V -65 to +150C 2kV HBM
RECOMMENDED OPERATING CONDITIONS
DC supply voltages (VCC) +5V 5% Operating temperature (TA) 0C to +70C (+25C typ.) 750mW (typ.) Power dissipation (P D)
ELECTRICAL CHARACTERISTICS
Recommended operating conditions apply except where stated. Characteristic DC characteristics Total VCC supply current TTL high level I/P voltage TTL low level I/P voltage TTL high level I/P current TTL low level I/P current EQSEL high level I/P voltage EQSEL low level I/P voltage EQSEL floating level I/P EQSEL high level I/P current EQSEL low level I/P current TTL high level O/P voltage TTL low level O/P voltage TTL high level O/P current TTL low level O/P current Transmit O/P current pins TXOP, TXON Differential RX I/P signal voltage RX I/P common mode voltage RX I/P impedance Signal detect threshold Low voltage shutdown PLL characteristics 3dB bandwidth Damping factor Peaking Overshoot Static error Jitter VCO characteristics Centre frequency Deviation Gain @125MHz 40 70 125 MHz MHz/V MHz 50 2 0.5 .005 5 0.5 dB % ns ns kHz VTH ICC VIH VIL IIH IIL VIH VIL VIZ IIH IIL VOH VOL IOH IOL 2 4.2 2.4 150 VCC/2 40 1.4 VCC/2 50 3.8 0.8 20 -400 0.8 1400 -1400 0.5 -200 4 24 mA V V A A V V V A A V V A mA mA Vp-p V % V RREF = 1300 100Mb/s data measured on device pins 100Mb/s data, 0mCable RX I/Ps floating k wrt normalized output of equalizer VIH = VCC VIL = 0V IOH = 20A IOL = 4mA device only VIH = VCC VIL = 0.4V Symbol Min. Value Typ. Max. Units Conditions
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NWK914D
TTLVCC
LFTA
LFTB
RXPLLVCC TXPLLVCC
TXOE
TXREF
10TXIN
10TX IP
TDLVCC
N10/100
RDLVCC
REFCLK TXC TDAT0 TDAT1 TDA T2 TDAT3 TDAT4 BGAPVCC BGAPGND RXC RDAT0 RDAT1 RDAT2 RDAT3 RDA T4
TIMES FIVE CLOCK MULTIPLIER
125 MHz
LOW VOLTAGE SHUT DOWN
CURRENT REFERENCE 10 Mb/s
TXVCC
SHIFTER & NRZ to NRZI
B AND GAP VOLTAGE REFERENCE
NRZI to MLT-3
100 Mb/s
TXOP TXON TXGND
DIVIDE CLOCK by FIVE
CLOCK RECOVERY PLL,125MHZ
TTL 3 LEVEL
LBEN
SHIFTER & NRZI to NRZ
COMPARATORS MLT-3 to NRZI
ADAPTIVE EQUALIZER
EQSEL RXIP RXIN RXVCC 2
TTL
SIGNAL DETECT
RXV CC1 RXGND SUBGND
TTLGND1 TTLGND2
LFRA
LFRB
SDT
RXPLLGND TXPLLGND TESTIP
TEST
Fig.3 System block diagram
FUNCTIONAL DESCRIPTION
The functional blocks within the device are shown in Fig. 3. These are described below:NRZ to MLT3 Encoder The serial data from the shifter then passes through an encoder which converts the NRZI binary data into the three level MLT-3 format for transmission by the 'TXO' outputs. Transmit Line Drivers There are two on-chip Line Drivers both of which share the output pins TXOP and TXON. The N10/100 pin is used to control which driver is active and allowed to drive the line. When held high the MLT-3 data is output by the 100Mb/s driver. This driver consists of differential current source outputs with programmable sink capability, designed to drive a nominal output impedance of 50. Output current is set by the value of an external resistor (R REF) between pin 'TXREF' and 'TXGND'. This resistor defines an internal reference current derived from an on-chip bandgap reference. Final output current at the 'TXO' outputs is a multiple of this current and is defined as:I
TXO(mA)
Transmit Section
Times Five Clock Multiplier 25MHz to 125MHz This circuit consists of a phase lock loop (PLL) that is operating at 125MHz, centre frequency. The 125MHz is divided by 5 to produce a 25MHz clock which is phase compared with a 25MHz crystal clock reference frequency which is input on pin REFCLK. The 25MHz clock (pin TXC) is then sent to the PCS layer to clock in in the 5 bit nibble data. Pins LFTA and LFTB are provided to set the VCO characteristics. The recommended loop filter components are shown in Fig.6. A control current is derived from the clock multiplier and is used by the receive clock recovery circuit to centre the PLL when no input data is present. Five Bit Nibble to 125MHz Shifter Data is input to the transmit side in 5 bit wide parallel form on pins TDAT0 through TDAT4. This NRZ data is clocked in on the positive edge of the 25MHz clock pin TXC. The parallel data is first loaded into a 5 bit wide register prior to being loaded into a 5 bit PISO where it is converted into a serial data stream. The last stage of the shifter incorporates a converter to change the data from NRZ to NRZI.
= 52/RREF(k)
Transition times of the 'TXO' outputs are matched and internally limited to approx. 2.5ns to reduce EMI emissions.
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NWK914D
When N10/100 is held low the 10Mb/s driver is selected. This 10Mb/s driver consists of a differential analog buffer designed to take a fully cable conditioned 10Mb/s signal from the filter output of existing 10BASE-T electronics. The 10BASE-T signal is input on pins 10TXIN and 10TXIP. The output current of the buffer is determined by the same external RREF resistor on pin TXREF as used for the 100Mb/ s driver. The unselected driver is switched to a tristated power save mode. A low voltage shutdown circuit turns off both TX drivers when V CC voltage falls to a level below the specified minimum. When operating in single 100Mb/s applications a 1:1 turn ratio magnetics will be used and therefore to attain the desired line driving current of 40mA out of the secondary a TXO output drive of 40mA is required. Using the above formula it will be found that 1.3 is the nearest prefered value to that required to give the 40mA. In the case of dual 10Mb/s and 100Mb/s applications a 2:1 turn ratio magnetics is recommended. The use of 2:1 magnetics enables a greater efficiency to be gained from the 10Mb/s driver by using a lower output current. At the same time this lower current is also true of the 100Mb/s output where now only a 20mA drive is required. An RREF value of 2.6K is used to set this current. Internal current ratioing within the device will ensure that the correct drive current is chosen depending upon whether the drives are in 10Mb/s or 100Mb/s mode as selected by pin N10/100. The RREF value can be adjusted to compensate for different magnetics and board layouts. The object is to achieve an output level of 2V p-p measured at the RJ45 socket in compliance with 802.3. When the TXOE pin is held low the TXdrivers are tristated regardless of the mode selected by the N10/100 pin. Base Line Wander Correction MLT-3 codes have significant low frequency components in their spectrum which are not transmitted through the transformers that couple the line to the board. This results in 'Base Line Wander', which can significantly reduce the noise immunity of the receiver. The purpose ot the correction circuit is to restore these low frequency components through the use of a feedback arrangement. The circuit will also correct any DC offset that may exist on the receive signal. Signal Detector A signal detect circuit is provided which continuously monitors the amplitude of the input signal being received on pins RXIP and RXIN. After the input signal reaches the specified level which the equalizer can correctly equalize, SDT is asserted high. Conversely if the signal level falls below a limit for reliable operation then SDT will go low. Comparators MLT-3 to NRZ Decoder The equalized MLT-3 data is then passed to a set of window comparators which are used to determine the signal level. The comparator outputs are OR'ed together to reconstitute the NRZI data. PLL Clock Recovery This function consists of a 125MHz PLL that is locked to the incoming data stream. The PLL is first centred to the transmit clock multiplier using an internal analog reference signal. Once a valid input signal is present, the PLL will lock to, and thus extract the clock from, the incoming data stream. Pins LFRA and LFRB are provided to set the VCO characteristics. The recommended loop filter components are shown in Fig.6. 125MHz Shifter to Parallel Data The 125Mb/s serial data stream with an accompanying phase related 125MHz clock is output from the PLL. This data stream is clocked into the serial to parallel register using the 125MHz clock. This data is then latched prior to being clocked out on pins RDAT0 to RDAT4. A 25MHz clock, derived from the 125MHz PLL by a divide by 5, is used to clock the parallel data and is output to pin RXC. Loopback Logic Pin `LBEN' controls loopback operation. A low level on this pin defines normal operation, a high level defines loopback mode. In loopback mode, the transmit data is internally routed to the receive circuitry, SDT is forced high and the TXOP and TXON outputs are disabled. Test Pins and No-Connects Two pins are provided on the product to aid testing in production. These pins TEST(38), and TESTIP(37) must be left unconnected for normal operation in application circuits. Additionally, there are four No-Connect pins (2,3,7,8) which also mustt be left unconnected for normal operation.
Receiver Section
Equalizer The equalizer circuit is necessary to compensate for signal degradation due to cable losses, however overequalization must be avoided to prevent excessive overshoots resulting in errors during the reception of MLT-3 data. Three operating modes are therefore provided. These three operating modes are controlled by the state of tristate input 'EQSEL' and are described below:1) Auto Equalization ('EQSEL' floating) Fully automatic equalization is achieved through the use of a feedback loop driven by a control signal derived from the signal amplitude. This provides adaptive control and prevents over-modulation of the signal when short cable lengths are used. 2) Full Equalization ('EQSEL' low) In this mode, full equalization is applied to the input signal irrespective of amplitude. 3) No Equalization ('EQSEL high) The equalization circuit is disabled completely during this mode.
4
NWK914D
AC CHARACTERISTICS
Recommended operating conditions apply except where stated. Characteristic AC characteristics 100Mb/s TX driver outputs rise/fall times pins TXOP, TXON REFCLK frequency REFCLK tolerance REFCLK M/S ratio REFCLK to TXC propagation delay TDAT0 4 to TXC setup time TDAT0 4 to TXC hold time RDAT0 4 valid to RXC +Ve edge RXC to RDAT0 4 invalid RXC M/S ratio REFCLK to SDT transition 1 2 3 4 5 6 7 8 9 40:60 5 12 0 10 10 45:55 5 2.5 25 100 60:40 13 55:45 15 ns MHz ppm % ns ns ns ns ns % ns Tx PLL in lock 100 differential load measured at RJ45 Waveform Timing Min. Value Typ. Max. Units Conditions
NOTE: Conditions for AC Characteristics: All AC measurementsare made at aVth + 1.5V and with TTL output loaded with 25pf
4
REFCLK
1 2 3
TXC
5 6
TDAT 04 TXO
VALID DATA
VALID DATA
bit 4
bit 3
bit 2
bit 1
bit 0
bit 4
Fig.4 Transmit timing waveform
9
RXC
5 8 VALID DATA
RDAT 04
Fig.5 Receive timing waveform
5
NWK914D
Pin Name SYMBOL Interface RXC SDT TDAT4 TDAT3 TDAT2 TDAT1 TDAT0 TXC RDAT0 RDAT1 RDAT2 RDAT3 RDAT4 Network Interface RXIP RXIN TXON TXOP Pin Type Pin Number Pin Description
TTLOP TTLOP TTLIP TTLIP TTLIP TTLIP TTLIP TTLOP TTLOP TTLOP TTLOP TTLOP TTLOP analog input analog input analog output analog output
4 5 40 41 42 43 44 47 48 49 50 51 52 15 16 22 23
25MHz recovered receive clock. This is aligned with and used to clock out the 5 bit parallel receive data to the PCS layer. Signal detect output. This output is high when an input signal of sufficient amplitude is detected on the RXI inputs. The 100BASE-TX transmit input bit 4 The 100BASE-TX transmit input bit 3 The 100BASE-TX transmit input bit 2 The 100BASE-TX transmit input bit 1 The 100BASE-TX transmit input bit 0 25MHz transmit clock. This is aligned with and used to clock in the 5 bit parallel 100BASE-TX transmit data from the PCS layer. The 100BASE-TX receive output bit 0 The 100BASE-TX receive output bit 1 The 100BASE-TX receive output bit 2 The 100BASE-TX receive output bit 3 The 100BASE-TX receive output bit 4 + Differential receive signal input from magnetics - Differential receive signal input from magnetics - Differential transmit line driver outputs to magnetics + Differential transmit line driver outputs to magnetics
10BASE-T Interface 10TXIN analog input 10TXIP analog input Control Pins N10/100 TTLIP
19 20 36
The filtered 10BASE-T transmit input (-) The filtered 10BASE-T transmit input (+) 10/100 mode selection. A low selects the 10BASE-T mode and enables the data on pins 10TXIP/N to be outut on the TXOP/N pins. A high selects the 100BASE-TX mode, enabling the 100Mb/s drivers. Mode select input for equalizer. Normally this pin is left unconnected (floating) for auto-eq. mode. High selects minimum equalization. Low selects full equalization. Loopback enable input. A high on this pin selects the loopback mode and low selects normal operation. Transmit output enable. A high on this pin selects normal operation. A low on this pin puts both of the TX drivers in tri-state mode. Test pin. This pin must be left unconnected for proper operation. Test pin. This pin must be left unconnected for proper operation. No connection. This pin must be left unconnected for proper operation. 25MHz clock input. An external 25MHz oscillator is input to this pin. TXOP/N line driver current setting pin. Connects to TXGND through a resistor. Differential loop filter pin for receive PLL (see fig.6) Differential loop filter pin for receive PLL (see fig.6) Differential loop filter pin for transmit clock PLL (see fig.6) Differential loop filter pin for transmit clock PLL (see fig.6) GND for TTL logic I/Os +5V supply to receive logic GND to receive PLL +5V supply to receive PLL +5V supply to adaptive equalizer and QFB circuits GND to to adaptive equalizer and QFB circuits +5V supply to MLT-3 to NRZI converter +5V supply to transmit line driver circuits GND to transmit line driver circuits +5V supply to on-chip bandgap reference Chip substrate GND connection GND to on-chip bandgap reference GND to to transmit clock-multiplier PLL +5V supply to transmit clock-multiplier PLL +5V supply to transmit logic +5V supply to TTL logic I/Os
EQSEL LBEN TXOE TESTIP TEST N/C
3 level IP TTLIP TTLIP test test
18 35 33 37 38 2,3,7,8 45 25 10 11 30 31 1,39 6 9 12 13 14 17 21 24 26 27 28 29 32 34 46
Component Connections REFCLK TTLIP TXREF analog input LFRB analog LFRA analog LFTB analog LFTA analog Power TTLGND RDLVCC RXPLLGND RXPLLVCC RXVCC2 RXGND RXVCC1 TXVCC TXGND RXVCC SUBGND BGAPGND TXPLLGND TXPLLVCC TDLVCC TXLVCC Power Power Power Power Power Power Power Power Power Power Power Power Power Power Power Power
Table 1: Pin descriptions
6
NWK914D
1K Xtal Osc. R1 100pF C1 LFTA REFCLK LFTB TXREF .033F C2 See Table 2 for these resistor values TxVcc R2 R5 TXGND TXOP 0.1F PCS or MAC (with embedded PCS) 5 TDAT0-4 TXON TXC RXC C4 CT 1:1 M A G N E T I C S R6
NWK914D
RXIP R9
15 R7 68 R8 15
RJ45
5
RDAT0-4 LFRA LFRB C3 R3 6.2K .01F
RXIN
Fig.6 Simplified 100BASE-TX system block diagram showing NWK914D external components
REF. C1 C2 C3 R1 R2 R3 R5,R6 R7,R8 R9 R2 R5,R6 VALUE 100pF 0.033F .01F 1K 1300 6.2K 50 15 68 2.6K 200 TOL. 20% 20% 20% 1% 1% 1% 1% 1% 1% 1% 1% FUNC. loop fltr loop fltr loop fltr loop fltr tx ref loop fltr xmit rcv pad rcv pad tx ref xmit 1:1 magnetics 1:1 magnetics NOTES
EXTERNAL REQUIREMENTS
The NWK914D requires a number of external components for the device to function correctly and these are shown in the simplified 100BASE-TX application circuit in Fig.6 and the component value information given in Table 2. Note that the values of R2, R5 and R6 vary depending upon application. When using 1:1 magnetics, use the values shown in the middle of Table 2 with note "1:1 magnetics". When using 2:1 magnetics use the values shown in the last two lines of Table 2. Please refer to the Transmit Line Driver section on pages 3-4 for more information on these values. For more detailed Application information please contact your local Sales Office.
2:1 magnetics 2:1 magnetics 2:1 magnetics
GLOSSARY OF TERMS AND ABREVIATIONS
MAC MLT-3 NRZ NRZI PCS PHY PLL PMD UTP RX STP TX UTP VCO Media Access Control Multi Level Transmit -3 levels Non Return To Zero Non Return to Zero Inverse Physical Coding Sublayer PHYsical Layer Phase Locked Loop Physical Media Dependent Unshielded Twisted Pair Receive Shielded Twisted Pair Transmit Unshielded Twisted Pair Voltage Controlled Oscillator NWK914S improved to 100m 680 NWK914D improved to 100m 1300
CT on transformer connects directly to TX VCC with C4 omitted
Table 2: External components
NWK914B Base Line Wander Correction TXREF resistor with 1:1 magnetics 620
Table 3: Differences between NWK914B, NWK914S and NWK914D
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