Dual-Slot PCMCIA

Analog Power Controllers

6

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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