MAX11068EVKIT+ Maxim Integrated Products, MAX11068EVKIT+ Datasheet - Page 73

• Manufacturer Part Number: MAX11068EVKIT+
• Description: KIT SMART BATT MEASUREMENT 12CH
• Manufacturer: Maxim Integrated Products

Specifications of MAX11068EVKIT+

• Main Purpose: Power Management, Battery Monitor, Car
• Utilized Ic / Part: MAX11068
• Primary Attributes: Monitors Current, Voltage, Temperature
• Secondary Attributes: 1 ~ 12 Cell- Li-Ion, 1 ~ 12 Cell- NiMH
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Embedded: -

The SHDN pin of the MAX11068 is connected in a man-
ner that allows the shutdown/wakeup command to trickle
up through the series of SMBus-laddered packs. The
propagation time is on the order of 3ms per module with
the recommended shutdown circuit. The shutdown func-
tion is intended to be a reset and power-saving mode
for the entire IC. When coming out of shutdown mode,
the device goes through the power-up sequence shown
for the linear regulator once the SHDN pin is above the
inactive state threshold. The shutdown function must still
operate when the VAA is shut down, so it cannot depend
on a Schmitt trigger. A special low-current, high-voltage
circuit is used to detect the state of the SHDN pin. The
shutdown pin has a +1.8V threshold. When SHDN >
1.8V, the MAX11068 turns on and begins regulating
VDD
down. Figure 46 shows the shutdown circuit interface of
two SMBus ladder devices.
When SHDN is high for the device, the charge pump
is enabled and begins to charge the capacitors in the
interface circuit. When the voltage of the SHDN pin for
device (n+1) rises above the V
begins its power-up sequence. This action propagates
up the SMBus ladder until the last battery module is
enabled. Conversely, pulling SHDN to GND
down a module and thus propagates the power down
to all higher SMBus-laddered modules as the charge on
their SHDN capacitors is dissipated. The zener diodes
provide additional ESD protection. The filter capacitors
and resistors are sized to provide robust noise immunity.
The diode from the CP+ pin should be S1B or a similar
low-leakage type for high-temperature stability.
The SHDN pin is a high-voltage input rated to 60V. SHDN
may be tied to DCIN through a resistor instead of using the
interface circuit above for applications that do not require
use of the shutdown mode. The resistor in that case is
necessary for failure-mode effects analysis considerations.
Figure 46. Shutdown Circuit Interface
U
and VDD
L
. If SHDN < 0.6V, the MAX11068 shuts
12-Channel, High-Voltage Sensor, Smart
DEVICE
Shutdown Control
(n)
GND
IH
CP+
U
threshold, that device
5.6V
S1B
150I
100nF
L
powers
Data-Acquisition Interface
1kI
5.6V
If SHDN was shorted to the ALRM
must be protected from seeing the full DCIN voltage. A
resistor value of 100kI is recommended to work across
the entire DCIN voltage range.
The SHDN pin has a weak internal pulldown resistor in
the order of 12MI. So, a 200kI or similar resistor from
SHDN to GND
SHDN pin is pulled low when the active SHDN signal
is propagated up the SMBus ladder. This resistor is not
needed for applications that tie SHDN high at all times.
When the MAX11068 becomes functional after any reset
event, its I
in the SMBus ladder are set to a default value. Prior to
performing battery-monitoring tasks, each device must
be configured to operate as part of the SMBus ladder.
The following configuration sequence (Figure 47) is rec-
ommended to initialize the system of SMBus-laddered
modules after a power cycle or change in the number of
battery stack modules.
First, the HELLOALL command is sent to sequentially ini-
tialize the individual device addresses. The first device
address is specified in the command byte and should
be chosen carefully based on the application require-
ments. After a successful HELLOALL command, the
ROLLCALL command should be sent. This reads the
ADDRESS register of all properly communicating mod-
ules. When the host sees two consecutive 0xFF bytes,
meaning that all valid data has been received, it should
send a NACK and a STOP bit to halt data flow. Once
the ADDRESS register data is received, the host can
determine how many devices are active on the bus. After
ensuring that the number of active devices matches
what is expected by the application, the host should
send the SETLASTADDRESS command to configure the
last device in the chain to be the heartbeat initiator.
68nF
2
200kI
C address, broadcast address, and place
L
should be installed to ensure that the
Initialization Sequence
SHDN
GND
L
DEVICE
(n+1)
I
2
C SMBus Ladder
L
pin, the ALRM
L
pin
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