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MAX613 Datasheet(PDF) 6 Page - Maxim Integrated Products |
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MAX613 Datasheet(HTML) 6 Page - Maxim Integrated Products |
6 / 8 page Dual-Slot PCMCIA Analog Power Controllers 6 _______________________________________________________________________________________ VCC Switching The MAX613/MAX614 contain level shifters that simplify driving external power MOSFETs to switch PCMCIA card VCC. While a PCMCIA card is being inserted into the socket, the VCC pins on the card edge connector should be powered down to 0V to prevent “hot insertion” that may damage the PCMCIA card. The MAX613/MAX614 MOSFET drivers are open drain. Their rise time is con- trolled by an external pull-up resistor, allowing slow turn- on of VCC power to the PCMCIA card. The DRV3 and DRV5 pins on the MAX613 and the DRV pin on the MAX614 are open-drain outputs pulled down with internal N-channel devices. The gate drive to these internal N-channel devices is powered from VCCIN, regardless of VPPIN’s voltage. If VCCIN is left unconnected or less than 2V is applied to VCCIN, the DRV3/DRV5/DRV gate drivers will not sink current. To switch VCC (M1 and M2 in Figure 1), use external N-channel power MOSFETs. M1 and M2 should be logic-level N-channel power MOSFETs with low on resistance. The Motorola MTP3055EL and Siliconix Si9956DY MOSFETs are both good choices. Turn on M1 and M2 by pulling their gates above +5V. With the gates pulled up to VPPIN as shown in Figure 1, VPPIN should be at least 10V so that with VCC = 5.5V, M1 and M2 have at least 4.5V of gate drive. The gates of M1 and M2 can be pulled up to any 10V to 20V source, and do not need to be pulled up to VPPIN. Typically, the +12V used for VPPIN is supplied from a +5V to +12V switching regulator. To save power, the +5V to +12V switching regulator can be shut down when not using the VPP programming voltage, allowing VPPIN to fall below +5V. In this case, M1 and M2 should not be pulled up to VPPIN, since M1 and M2 cannot be turned on reliably when VPPIN falls below +10V. Any clock source can be used to generate a high-side gate-drive voltage by using capacitors and diodes to build an inexpensive charge pump. Figure 3 shows a charge-pump circuit that generates 10V from a +5V logic clock source. __________Applications Information The MAX613 contains all the gate drivers and switch- ing circuitry needed to support a +3.3V/+5V VCC PCMCIA slot with minimal external components. Figure 4 shows the analog power control necessary to support two dual voltage PCMCIA slots. The A:VCC and B:VCC pins on the Intel 82365SL DF power the drivers for the control signals that directly connect to the PCMCIA card. A 3.3V card needs 3.3V logic-level control signals and the capability to program VPP1 and VPP2 to 3.3V. The MAX613’s VCCIN is switched with slot VCC, so AVPP0 = 1 and AVPP1 = 0 causes AVPP = slot VCC. Likewise, A:VCC and B:VCC are connected to VCCIN, so the Intel 82365SL DF control signals to the PCMCIA card are the right logic levels. PCMCIA card interface controllers other than the Intel 82365SL DF can be used with Figure 4’s cir- cuit. Table 4 shows the pins on the Cirrus Logic CL-PD6720 that perform the same function as the Intel 82365SL DF pins. LOGIC INPUT AVPP1 AVPP0 AVPP 0 0 0V 0 1 VCCIN 1 0 VPPIN 1 1 HI-Z OUTPUT LOGIC INPUT VCC1 VCC0 DRV3 DRV5 0 0 0V 0V 0 1 HI-Z 0V 1 0 0V HI-Z 1 1 0V 0V LOGIC INPUT OUTPUT BVPP1 BVPP0 BVPP 0 0 0V 0 1 VCCIN 1 0 VPPIN 1 1 HI-Z Table 3. MAX613 DRV3 and DRV5 Control Logic ( – S — H — D — N = VCCIN) OUTPUT Table 1. AVPP Control Logic Table 2. BVPP Control Logic |
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