DS2438Z/T&R Maxim Integrated Products, DS2438Z/T&R Datasheet - Page 5

• Manufacturer Part Number: DS2438Z/T&R
• Description: IC MONITOR SMART BATTERY 8-SOIC
• Manufacturer: Maxim Integrated Products

Specifications of DS2438Z/T&R

• Function: Fuel, Gas Gauge/Monitor
• Battery Type: Smart Batteries
• Voltage - Supply: 2.4 V ~ 10 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

VOLTAGE REGISTER FORMAT Table 2
For applications requiring a general purpose voltage A/D converter, the DS2438 can be configured so that
the result of a Convert V command will place the scaled binary representation of the voltage on the V
input (as opposed to the V
Depending upon the state of the Status/Configuration Register, either (but not both) the V
voltage will be stored in the Voltage Register upon receipt of the Convert V command. Refer to the
description of the Status/Configuration Register in the Memory Map section for details. If the V
is used as the voltage input, the A/D will be accurate for 1.5V < V
5.0V. This feature gives the user the ability to have a voltage A/D that meets spec accuracy for inputs
over the entire range of 1.5V < V
OPERATION - MEASURING BATTERY CURRENT
The DS2438 features an A/D converter that effectively measures the current flow into and out of the
battery pack by measuring the voltage across an external sense resistor. It does so in the background at a
rate of 36.41 measurements/sec; thus, no command is required to initiate current flow measurements.
However, the DS2438 will only perform current A/D measurements if the IAD bit is set to “1” in the
Status/Configuration Register. The DS2438 measures current flow in and out of the battery through the
V
current sense resistor, R
V
diagram in Figure 1). Using a 100 kW (min) resistor (R
cutoff is approximately 15.9 Hz. The current A/D measures at a rate of 36.41 times per second, or once
every 27.46 ms. This filter will capture the effect of most current spikes, and will thus allow the current
accumulators to accurately reflect the total charge which has gone into or out of the battery.
The voltage across current sense resistor R
Current Register in two’s complement format. The sign (S) of the result, indicating charge or discharge,
resides in the most significant bit of the Current Register, as shown in Table 3. See “Memory Map” in
Figure 7 for the Current Register address location.
SENS
SENS-
, we recommend use of an RC low pass filter between it and the GND end of R
pins; the voltage from the V
VOLTAGE
BATTERY
0.05V
9.99V
2.7V
3.6V
7.2V
10V
5V
MSb
2
0
SENS
7
DD
. The V
2
0
6
input) into the Voltage Register in the same format described in Table 2.
AD
2
0
5
SENS+
< 10V for V
SENS+
DIGITAL OUTPUT (Binary)
(unit = 10 mV)
2
0
4
pin to the V
terminal may be tied directly to the R
0000 0000 0000 0101
0000 0001 0000 1110
0000 0001 0110 1000
0000 0001 1111 0100
0000 0010 1101 0000
0000 0011 1110 0111
0000 0011 1110 1000
SENS
2
0
3
DD
is measured by the ADC and the result is placed in the
= 5.0V.
5 of 29
2
0
2
SENS-
F
) and a 0.1 mF tantalum capacitor (C
2
2
1
9
pin is considered to be the voltage across the
LSb
2
2
0
8
AD
MSB
LSB
< 2V
DD
DIGITAL OUTPUT (Hex)
over the range 2.4V < V
SENS
resistor, however, for
03E8H
02D0h
010Eh
01F4h
03E7h
0005h
0168h
SENS
(see the block
F
), the filter
DD
AD
or V
input
DD
AD
AD
<