MAX1601 Maxim, MAX1601 Datasheet - Page 11

• Manufacturer Part Number: MAX1601
• Description: Dual-Channel CardBus and PCMCIA Power Switches with SMBus Serial Interface
• Manufacturer: Maxim

The MAX1601/MAX1604 power-switching ICs contain a
network of low-resistance MOSFET switches that deliver
selectable VCC and VPP voltages to two Cardbus or
PC Card host sockets. The MAX1601/MAX1604 differ
only in the VY switch on-resistance. Figure 1 is the
detailed block diagram.
The power-input pins (VY, VX, 12IN_) are completely
independent. Low inrush current is guaranteed by con-
trolled switch rise times. VCC’s 100µs minimum output
rise time is 100% tested with a 1µF capacitive load, and
VPP’s 1ms minimum rise time is guaranteed with a 0.1µF
load. These respective capacitive loads are chosen as
worst-case card-insertion parameters. The internal
switching control allows VCC and VPP rise times to be
controlled, and makes them nearly independent of resis-
tive and capacitive loads (see rise-time photos in the
Typical Operating Characteristics ). Fall times are a
function of loading, and are compensated by internal
circuitry.
Power savings is automatic: internal charge pumps draw
very low current when the VCC switches are static.
Standby mode reduces switch supply current to 1µA.
Driving the VL pin low with an external logic gate (master
shutdown) reduces total supply current to1µA (Figure 2).
The MAX1601/MAX1604 have three operating modes:
normal, standby, and shutdown. Normal mode supplies
the selected outputs with their appropriate supply volt-
ages. Standby mode places all switches at ground, high
impedance, or a combination of the two. Shutdown mode
turns all switches off, and puts the VCC and VPP outputs
into a high-impedance state. Pull VL low to enter shutdown
mode. To ensure a 0.05V/µs fall rate on VL, use a 1kΩ
series resistor and a 0.1µF capacitor to ground (Figure 2).
Peak detecting circuitry protects both the VCC and
VPP switches against overcurrent conditions. When
current through any switch exceeds the internal current
limit (4A for VCC switches and 200mA for VPP switch-
es), the switch turns off briefly, then turns on again at
the controlled rise rate. If the overcurrent condition
lasts more than 2µs, the SMBALERT output latches
_______________Detailed Description
Power Switches with SMBus™ Serial Interface
______________________________________________________________________________________
Overcurrent Protection
Dual-Channel CardBus and PCMCIA
Operating Modes
low. A continuous short-circuit condition results in a
pulsed output current until thermal shutdown is
reached. SMBALERT is open-drain and requires an
external pull-up resistor.
If the IC junction temperature rises above +150°C, the
thermal shutdown circuitry opens all switches, including
the GND switches, and SMBALERT is pulled low. When
the temperature falls below +130°C, the switches turn
on again at the controlled rise rate. If the overcurrent
condition remains, the part cycles between thermal
shutdown and overcurrent.
If the VX or VY switch input voltage drops below 1.5V,
the associated switch turns off and SMBALERT goes
low. For example, if VY is 3.3V and VX is 0V, and if the
interface controller selects VY, the VCCA output will be
3.3V. If VX is selected, VCCA changes to a high-imped-
ance output and SMBALERT goes low.
When a voltage is initially applied to 12IN_, it must be
greater than 8V to allow the switch to operate.
Operation continues until the voltage falls below 2V (the
VPP output is high impedance).
When VL drops to less than 2.3V, all switches are
turned off and the VCC and VPP outputs are high
impedance.
Figure 2. Master Shutdown Circuit
SHUTDOWN
MASTER
74HC04
0.1 F
1k
Undervoltage Lockout
VL
Thermal Shutdown
MAX1601
MAX1604
3.3V
VY
VCCA
VCCB
VPPA
VPPB
TO
SOCKETS
A AND B
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