MAX1660 Datasheet, PDF (13/20 Pages) Maxim Integrated Products – Digitally Controlled Fuel-Gauge Interface

Digitally Controlled
Fuel-Gauge Interface
OCO and ODO Gate Drivers
OCO and ODO are open-drain N-channel MOSFET out-
puts that drive the external P-channel MOSFET gates.
Connect pull-up resistors in the 500kΩ to 1MΩ range
from OCO and ODO to BATT to reduce current draw
when OCO and ODO are driven low. For additional pro-
tection of OCO and ODO from voltage spikes coupled
through the MOSFET gate capacitance, place 10kΩ
resistors (R9 and R10) from OCO and ODO to the
respective MOSFET gates (Figure 8). To protect the
battery pack and load during power-up, OCO and
ODO are forced into a high-Z state during the power-
on-reset timeout period. Table 4 shows the truth tables
defining the OCO and ODO output states with respect
to the overcurrent comparators and the MAX1660’s
configuration bits.
INT Output
The MAX1660’s INT output drives an optional third wire
that interrupts the host whenever an alert condition
occurs. The MAX1660’s host-interrupt procedure is
compatible with the SMBus SMBALERT# signal, but it is
equally useful as a simple host-interrupt output.
By default, an interrupt is triggered (INT is pulled low) any
time an overcurrent condition occurs (see the Overcurrent
Detection section). The MAX1660 may also be configured
to generate an interrupt whenever a digital compare
equality occurs and/or when a change in the current-flow
direction is detected (see the Digital Compare Function
and Direction-Change Detection Function sections).
Once triggered, INT stays low until the interrupt is
cleared. An interrupt is cleared when one of three con-
ditions is true: a 1 is written into the configuration
word’s CLRINT bit, the MAX1660 acknowledges the
SMBus Alert Response Address (ARA), or a power-on
reset occurs. The MAX1660 acknowledges the ARA
with the 0 x 8F byte.
INT is an open-drain output; connect a 100kΩ pull-up
resistor between INT and VL.
Alert Response Address (0001100)
The Alert Response address provides quick fault identi-
fication for single slave devices that lack the complex,
expensive logic needed to be a BusMaster.
When a slave device generates an interrupt, the host
(BusMaster) interrogates the bus slave devices via a
special receive-byte operation that includes the Alert
Response address. The data returned by this read-byte
operation is the address of the interrupting slave
device. The MAX1660 when interrupted, will respond
with 0x8F.
RST Output
RST is an open-drain, active-low power-on reset output
provided for the MAX1660’s host controller and other
external circuitry. RST drives low on power-up whenev-
er the MAX1660 enters hard-shutdown mode, or when-
ever the VL regulator output is below V_TH1 (typically
1.7V). In hard-shutdown mode, RST goes low and
remains low as long as the VL regulator provides suffi-
cient gate drive to the RST output switch (typically until
VL falls to 1V), after which RST drifts slightly upward.
On power-up or when exiting hard-shutdown mode,
RST drives low until 25ms (typ) after VL exceeds V_TH2
(typically 2.9V). Although RST offers a reliable power-
on reset function, it does not detect brownout condi-
tions (V_TH1 < VL < V_TH2). For applications that require
brownout detection, refer to Maxim’s complete line of
precision microprocessor supervisory products.
Connect a 100kΩ pull-up resistor between RST and VL.
Leave RST unconnected if the power-on reset function
is not used.
Internal Regulator and Reference
The 3.3V VL internal linear regulator powers the
MAX1660 control circuitry, logic, and reference, and
can supply up to 5mA to power external loads, such as
a microcontroller or other circuitry. Bypass VL to GND
with a 0.33µF capacitor.
The 2.00V precision reference (REF) is accurate to
±2%, making it useful as a system reference. REF can
supply up to 200µA to external circuitry. Bypass REF to
GND with a 10nF capacitor.
Shutdown Modes
Hard Shutdown
Driving SHDN low puts the MAX1660 into hard-shut-
down mode and forces the power-on reset state. In
hard-shutdown mode, the VL regulator and the refer-
ence turn off, reducing supply current to 1µA (max). To
protect the battery pack and load during the power-on-
reset timeout period, the OCO and ODO outputs are
forced into their high-Z states. SHDN is a logic-level
input, but can be safely driven by voltages up to V_BATT.
Soft Shutdown
Drive the MAX1660 into soft-shutdown mode by setting
the configuration word’s SHDNSTATUS bit. All interrupts
clear in soft-shutdown mode. In this mode, only the VL
regulator and the SMBus interface remain active, reduc-
ing the supply current to just 15µA.
To prevent current from flowing undetected while the
MAX1660 remains in soft-shutdown mode, ensure that
the command to enter soft-shutdown mode contains a
*Patent pending
______________________________________________________________________________________ 13