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MC33996 Fiches technique(PDF) 10 Page - Freescale Semiconductor, Inc |
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MC33996 Fiches technique(HTML) 10 Page - Freescale Semiconductor, Inc |
10 / 24 page Analog Integrated Circuit Device Data 10 Freescale Semiconductor 33996 FUNCTIONAL DESCRIPTION FUNCTIONAL PIN DESCRIPTION FUNCTIONAL DESCRIPTION The 33996 is designed and developed for automotive and industrial applications. It is a 16 output power switch having 24 bit serial control. The 33996 incorporates SMARTMOS technology having CMOS logic, bipolar/MOS analog circuitry, and independent DMOS power output transistors. Many benefits are realized as a direct result of using this mixed technology. A simplified internal block diagram of the 33996 is shown in Figure 2, page 2. FUNCTIONAL PIN DESCRIPTION CHIP SELECT (CS) The system MCU selects the 33996 to be communicated with through the use of the Chip Select (CS) pin. When the CS pin is in a logic low state, data can be transferred from the MCU to the 33996 and vise versa. Clocked-in data from the MCU is transferred from the 33996 Shift register and latched into the power outputs on the rising edge of the CS signal. On the falling edge of the CS signal, output fault status information is transferred from the Power Outputs Status register into the device’s SO Shift register. The SO pin output driver is enabled when CS is low, allowing information to be transferred from the 33996 to the MCU. To avoid any spurious data, it is essential the high-to-low transition of the CS signal occur only when SCLK is in a logic low state. SYSTEM CLOCK (SCLK) The System Clock (SCLK) pin clocks the Internal Shift registers of the 33996. The Serial Input (SI) pin accepts data into the Input Shift register on the falling edge of the SCLK signal, while the Serial Output (SO) pin shifts data information out of the Shift register on the rising edge of the SCLK signal. False clocking of the Shift register must be avoided, ensuring validity of data. It is essential that the SCLK pin be in a logic low state whenever the CS pin makes any transition. For this reason, it is recommended, though not necessary, that the SCLK pin is commanded to a low logic state as long as the device is not accessed (CS in logic high state). When the CS is in a logic high state, any signal at the SCLK and SI pins is ignored and the SO is tri-stated (high impedance). SERIAL INPUT (SI) The Serial Input (SI) pin is used to enter one of seven serial instructions into the 33996. SI SPI bits are latched into the Input Shift register on each falling edge of SCLK. The Shift register is full after 24 bits of information are entered. The 33996 operates on the command word on the rising edge of CS. To preserve data integrity, exercise care not to transition SI as SCLK transitions from high to low state (see Figure 4, page 8). SERIAL OUTPUT (SO) The Serial Output (SO) pin transfers fault status data from the 33996 to the MCU. The SO pin remains tri-state until the CS pin transitions to a logic low state. All faults on the 33996 are reported to the MCU as logic [1]. Conversely, normal operating outputs with nonfaulted loads are reported as logic [0]. On the falling edge of the CS signal, output fault status information is transferred from the Power Outputs Status register into the device’s SO Shift register. The first eight positive transitions of SCLK will provide Any Fault (bit 23), over-voltage fault (bit 22), followed by six logic [0]s (bits 21 to 16). The next 16 successive positive transitions of SCLK provides fault status for output 15 to output 0. Refer to the LOGIC OPERATION section (below) for more information. The SI/SO shifting of data follows a first-in, first- out protocol, with both input and output words transferring the Most Significant Bit (MSB) first. OUTPUT DRIVER POWER SUPPLY (SOPWR) The SOPWR pin is used to supply power to the 33996 SO output driver and Power-ON Reset (POR) circuit. To achieve low standby current on VPWR supply, power must be removed from the SOPWR pin. The 33996 will be in reset with all drivers OFF when SOPWR is below 2.5V. The 33996 does not detect over-voltage on the SOPWR supply pin. OUTPUT/INPUT (OUT0–OUT15) These pins are low side output switches controlling the load. RESET (RST) The Reset (RST) pin is the active low reset input pin used to turn OFF all outputs, thereby clearing all internal registers. BATTERY INPUT (VPWR) The VPWR pin is used as the input power source for the 33996. The voltage on VPWR is monitored for over-voltage protection and shutdown. An over-voltage condition (> 50 μs) on the VPWR pin will cause the 33996 to shut down all outputs until the over-voltage condition is removed. Upon return to normal input voltage, the outputs will respond as programmed by the over-voltage bit in the Global Shutdown/ Retry Control register. The over-voltage threshold on the VPWR pin is specified as 27.5 to 35 V with 1.4V typical hysteresis. Following an over-voltage shutdown of output drivers, the over-voltage Fault and the Any Fault bits in the SO bit stream will be logic [1]. PWM CONTROL (PWM) The PWM Control pin is provided to support PWM of any combination of outputs. The LOGIC OPERATION section describes the logic for PWM control. |
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