MAX4825ETP-T Maxim Integrated Products, MAX4825ETP-T Datasheet - Page 12

• Manufacturer Part Number: MAX4825ETP-T
• Description: MOSFET & Power Driver ICs
• Manufacturer: Maxim Integrated Products

Specifications of MAX4825ETP-T

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

level data to the parallel register and updates the state
of the outputs. Address data entered after CS is pulled
low is not reflected in the state of the outputs following
the next low-to-high transition on CS (Figure 7).
The MAX4822–MAX4825 feature set and reset inputs
that allow simultaneous turn-on or turn-off of all outputs
using a single control line. Drive SET low to set all latch-
es and registers to 1 and turn all outputs on. SET over-
rides all serial/parallel control inputs. Drive RESET low
to clear all latches and registers and to turn all outputs
off. RESET overrides all other inputs including SET.
The MAX4822–MAX4825 feature power-on reset. The
power-on reset function causes all latches to be
cleared automatically upon power-up. This ensures that
all outputs come up in the off or high-impedance state.
The MAX4822/MAX4823 feature a digital output
(DOUT) that provides a simple way to daisy chain multi-
ple devices. This feature allows driving large banks of
relays using only a single serial interface. To daisy
chain multiple devices, connect all CS inputs together,
and connect the DOUT of one device to the DIN of
another device (see Figure 8). During operation, a
stream of serial data is shifted through the MAX4822/
MAX4823 devices in series. When CS goes high, all
outputs update simultaneously.
The MAX4822/MAX4823 can also be used in a slave
configuration that allows individual addressing of
devices. Connect all the DIN inputs together, and use
+3.3V/+5V, 8-Channel Relay Drivers with Fast
Recovery Time and Power-Save Mode
Figure 5. 3-Wire Serial-Interface Operation for MAX4822
12
SCLK
______________________________________________________________________________________
DIN
CS
A7
Applications Information
A6
A5
SET/RESET Functions
A4
Power-On Reset
Daisy Chaining
A3
A2
A1
A0
D7
the CS input to address one device at a time. Drive CS
low to select a slave and input the data into the shift
register. Drive CS high to latch the data and turn on the
appropriate outputs. Typically, in this configuration only
one slave is addressed at a time.
The MAX4822/MAX4824 feature a unique power-save
mode where the relay current, after activation, can be
reduced to a level just above the relay hold-current
threshold. This mode keeps the relay activated while
significantly reducing the power consumption.
In serial mode (MAX4822), choose between seven cur-
rent levels ranging from 30% to 90% of the nominal cur-
rent in 10% increments. The actual percentage is
determined by the power-save configuration register
(Figure 1).
In parallel mode (MAX4824), the power-save current is
fixed at 60% of the nominal current.
Every time there is a write operation to the device (CS
transitions from low to high), the MAX4822/MAX4824
start charging the capacitor connected to PSAVE. The
serial power-save implementation is such that a write
operation does not change the state of channels
already in power-save mode (unless the write turns the
channel OFF).
After a certain time period, t
capacitor value), the capacitor reaches a voltage
threshold that sets all active outputs to power-save
mode. The t
allow the relay to turn on completely. The time period
t
PS
can be adjusted by using different capacitor values
D6
D5
PS
period should be made long enough to
D4
D3
D2
PS
D1
Power-Save Mode
(determined by the
Power-Save Timer
D0