MAX780AEAG+T Maxim Integrated, MAX780AEAG+T Datasheet - Page 7

• Manufacturer Part Number: MAX780AEAG+T
• Description: Power Switch ICs - Power Distribution
• Manufacturer: Maxim Integrated

Specifications of MAX780AEAG+T

• Rohs: yes
• Number Of Outputs: 2
• On Resistance (max): 1.6 Ohms, 30 Ohms, 140 Ohms
• Operating Supply Voltage: 2.85 V to 5.5 V, 0 V to 12.6 V
• Supply Current (max): 0.13 mA
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: SSOP-24
• Maximum Power Dissipation: 640 mW
• Minimum Operating Temperature: - 40 C

If a mechanical interlock switch cannot be used, an
extra MOSFET must be added, as shown in Figure 1.
Placing two N-channel MOSFETs in series with their
body diodes facing in opposite directions allows V
be shut down to 0V without using a mechanical switch.
The drive to the external MOSFETs ensures that the
3.3V supply is never connected to the 5V supply. This
is done by turning these transistors off quickly (using
active pull-down circuitry), and on more slowly (using
external pull-up resistors). The turn-on delay depends
on the value of the pull-up resistors, and on the gate
capacitance of the switching transistors. To save
power, use high-value resistors of up to 10MΩ.
However, note that high-value resistors will increase the
time it takes to turn on the switched supplies
The MAX780 can be used with PCMCIA controllers
other than the Intel 82365SL DF. Figure 2 shows the
logic connections to the Cirrus Logic CL-PD6720
PCMCIA Host Adapter.
The MAX780 does not need a PCMCIA controller to
function. Tie C2 to VCCIN to allow direct V
control from the system bus. Figure 3 shows the con-
nection to the system bus. Figure 4 shows the timing
requirements.
In the Typical Operating Circuit, V
the PCMCIA ports using the 12V V
provides the gate drive needed to turn on the external
N-channel MOSFETs. In some cases, the high-power
V
written to the PCMCIA port, not when data is being
read. The V
several milliamps, so it consumes more power than is
necessary simply to provide gate drive for some FETs.
__________Applications Information
PP
supply is only available when information has to be
Dual-Slot PCMCIA Analog Power Controller
PP
without Using the V
Reading from a PCMCIA Port
supply may have a quiescent current of
_______________________________________________________________________________________
Switching Speed
CC
PP
is switched to
supply, which
PP
CC
Supply
and V
CC
PP
to
In these circumstances, a separate gate-drive supply is
needed to turn on the external FETs. Ideally it should
have a low quiescent current and be capable of being
turned off when read access to the PCMCIA port is not
required. Doubling or tripling charge pumps can easily
be built using a convenient clock signal from elsewhere
in the system. Buffering the clock signal with a suitable
gate provides on/off control, as shown in Figure 5.
When driven at 100kHz or more by a CMOS gate pow-
ered from 5V, the doubler circuit outputs 8.6V when
loaded with 25kΩ (equivalent to four 100kΩ pull-up
resistors). Under similar conditions, but when running
from 3.3V, the tripler circuit produces 7.9V.
Figure 1. Using an Extra MOSFET to Replace the Mechanical
* EXTRA MOSFET
NOTE: BODY DIODES OF MOSFETS SHOWN FOR CLARITY.
Interlock
MAX780_
ADRV5
ADRV3
BDRV5
BDRV3
VCCIN
100k
100k
100k
100k
+12V
+12V
+12V
+12V
+3.3V
*
*
+5V
1 F
1 F
AVCC
BVCC
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