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MC33990DR2 Scheda tecnica(PDF) 10 Page - Freescale Semiconductor, Inc |
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MC33990DR2 Scheda tecnica(HTML) 10 Page - Freescale Semiconductor, Inc |
10 / 16 page 33990 MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA 10 SYSTEM/APPLICATION INFORMATION INTRODUCTION The 33990 is a serial transceiver device designed to meet the SAE Standard J-1850 Class B performance for bi- directional half-duplex communication. The device is packaged in an economical surface-mount SOIC plastic package. An internal block diagram of the device is shown in Figure 1. The 33990 derives its robustness to temperature and voltage extremes from being built on a SMARTMOS process, incorporating CMOS logic, bipolar/MOS analog circuitry, and DMOS power FETs. Though the 33990 was principally designed for automotive applications requiring SAE J-1850 Class B standards, it is suited for other serial communication applications. It is parametrically specified over an ambient temperature range of -40 °C ≤ TA ≤ 125°C and 7.0 V ≤ VBAT ≤ 16 V supply. The economical 8-pin SOICN surface mount plastic package makes the device a cost-effective solution. FUNCTIONAL DESCRIPTION Input Power (VBAT Pin) This is the only required input power source necessary to operate the 33990. The internal voltage reference of the 33990 will remain fully operational with a minimum of 9.0 V on this pin. Bus transmissions can continue with battery voltages down to 5.0 V. The bus output voltage will follow the battery voltage down and, in doing so, track approximately 1.6 V below the battery voltage. The device will continue to receive and transmit bus data to the microcontroller with battery voltages as low as 4.25 V. The pin can withstand voltages from -16 V to 40 V. Sleep Input (SLEEP Pin) This input is used to enable and disable the Class B transmitter. The Class B receiver is always enabled so long as adequate VBAT pin voltage is applied. When the SLEEP pin voltage is 5.0 V, the Class B transmitter is enabled. If this input is 0 V, the Class B transmitter will be disabled and less than 65 µA of current will be drawn by the VBAT pin. The pin also provides a 5.0 V reference, internal to the device, used to establish the Rx output level and slew rate times. Class B Functional Description The transmitter provides an analog waveshaped 0 V to 7.0 V waveform on the BUS output. It also receives waveforms and transmits a digital level signal back to a logic IC. The transmitter can drive up to 32 secondary Class B transceivers (see Figures 9 and 10). These secondary nodes may be at ground potentials that are ±2.0 V relative to the control assembly. Waveshaping will only be maintained during 2 of the 4 corners when the 0 to ±2.0 V ground potential difference condition exists. The 33990 is a secondary node on the Class B bus. Each secondary transceiver has a 470 ±10% pF capacitor on its output for EMI suppression purposes, as well as a 10.6 k Ω ±5% pull-down resistor to ground. The primary node has a 3300 ±10% pF capacitor on its output for EMI suppression, as well as a 1.5 k Ω ±5% pull-down resistor to ground. With more than 26 nodes, there is no primary node (see Figure 11). All nodes will have a 470 ±10% pF capacitor and a 10.6 kΩ ±5% pull-down resistor. No matter how many secondary nodes are on the Class B bus, the RC time constant of the Class B bus is maintained at approximately 5.0 µs. The minimum and maximum capacitance and resistance on the Class B bus is given by the expressions shown in Table 1. Figure 9. Minimum Bus Load Figure 10. Maximum Number of Nodes Figure 11. Maximum Bus Load 3300 pF 1.5 k Ω 470 pF 10.6 k Ω One Primary Node 1.5 k Ω 470 pF 10.6 k Ω Primary Node 442 Ω 24 Secondary Nodes 3300 pF 11280 pF 14570 pF 342 Ω 470 pF 10.6 k Ω 31 Secondary Nodes Freescale Semiconductor, Inc. For More Information On This Product, Go to: www.freescale.com |
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