MAX1660 Datasheet, PDF (7/20 Pages) Maxim Integrated Products – Digitally Controlled Fuel-Gauge Interface

Digitally Controlled
Fuel-Gauge Interface
______________________________________________________________Pin Description
PIN NAME
FUNCTION
Open-Drain Host-Interrupt Output. INT sinks current when active, otherwise high-impedance (see INT
1
INT
Output section). INT is compatible with the SMBus SMBALERT# (the “#” indicates asserted low) signal.
Connect a 100kΩ pull-up resistor between INT and VL. Leave INT unconnected if host interrupt is not used.
2
SHDN Active-Low Shutdown Input (see Shutdown Modes section)
3
N.C.
No Connection. Not internally connected.
4
CS
Current-Sense Resistor Input
5
AGND Analog Ground
6
REF
2.00V Reference Output. Bypass REF to AGND with a 10nF capacitor (see Internal Regulator and Reference
section).
7
ODI
Discharge Overcurrent-Detection Input (see Overcurrent Detection section)
8
OCI
Charge Overcurrent-Detection Input (see Overcurrent Detection section)
9
GND Ground
10
VL
3.3V Linear-Regulator Output. Bypass VL with a 0.33µF capacitor to GND (see Internal Regulator and
Reference section).
11
BATT Supply Input
12
ODO
High-Voltage, Open-Drain MOSFET Gate-Driver Output. ODO controls activation of the battery-discharge
path (see OCO and ODO Gate Drivers section).
13
OCO
High-Voltage, Open-Drain MOSFET Gate-Driver Output. OCO controls activation of the battery-charge path
(see OCO and ODO Gate Drivers section).
14
RST
Active-Low Reset Output. Connect a 100kΩ pull-up resistor between RST and VL. Leave RST unconnected
if the power-on reset function is not used (see RST Output section).
15
SDA
Serial-Data Input/Output. Connect a 10kΩ resistor between SDA and VL (see SMBus Interface section).
16
SCL
Serial-Clock Input. Connect a 10kΩ resistor between SDA and VL (see SMBus Interface section).
_______________Detailed Description
The MAX1660 measures the cumulative charge into
(charging) and out of (discharging) the system battery
pack and stores the information in one of two internal,
independent charge and discharge counters. It
achieves battery-pack overcharge and overdischarge
protection through a powerful digital compare function
that interrupts the host CPU when the charge or dis-
charge counter reaches a host-programmed value. The
device also informs the host of changes in the direction
of current flow and protects the battery pack from
short-circuit and overcurrent conditions.
The MAX1660 incorporates a 2-wire System Man-
agement Bus (SMBus™)-compliant serial interface,
allowing access to charge/discharge counters and
internal registers. An optional third wire provides an
SMBALERT#-compliant interrupt signal, or it may be used
as a simple, stand-alone host interrupt.
Coulomb-Counting Interface
The MAX1660’s Coulomb-counting interface monitors
the charge flowing in either the charging or discharging
direction, and counts the Coulombs of charge by incre-
menting either the charge counter (CHGCOUNT) or the
discharge counter (DISCOUNT) accordingly. The num-
ber of counter increments generated per Coulomb of
charge sensed (conversion gain) is given by the follow-
ing equation:
A_C = 416.7 ⋅ 10³ R_CS
Counts
Coulomb
where R_CS is the current-sense resistor (see the Typical
Operating Circuit). The gain factor is the constant of
proportionality that relates the counter values stored in
CHGCOUNT and DISCOUNT to the amount of charge
flow into or out of the battery pack. A higher conversion
gain (larger R_CS) increases resolution at low currents,
*Patent pending
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