ds2437 Maxim Integrated Products, Inc., ds2437 Datasheet - Page 6

• Manufacturer Part Number: ds2437
• Description: Smart Battery Monitor
• Manufacturer: Maxim Integrated Products, Inc.

The current is measured by the ADC with a signed 10-bit (0.004883C) resolution, and the last completed
measurement is placed in the CURRENT REGISTER in a sign-extended 2’s-complement format. This
register is scaled such that a count of 205
current flow that can be measured is from -2.5C (discharging) to +2.5C (charging). The sign (S) of the
current measurement, indicating charge or discharge, resides in the seven most significant bits of the
CURRENT REGISTER, as shown in Table 3. See “Memory Map” section for the CURRENT
REGISTER address location.
Current/Data Relationships Table 3
For the DS2437 to output current data scaled as in Table 3, the user is responsible for selecting an R
that will provide a 100 mV drop across it at a 2C rate. However, this value could be changed to
correspond to a different rate as long as this is comprehended by the user’s software in interpreting the
results from the DS2437.
OPERATION – CURRENT ACCUMULATORS
The DS2437 keeps track of the remaining capacity of a battery through the Integrated Current
Accumulator (ICA). The ICA maintains a net accumulated total of current flowing into and out of the
battery; therefore, the reading in this register is an indication of the remaining capacity in a battery and
may be used in performing gas gauge functions. In addition, the DS2437 has a register that accumulates
battery charging (positive) current (CCA) and one that accumulates discharging (negative) current
(DCA). This gives the smart battery system information needed to determine the end of life of a
rechargeable battery, based on total charge/discharge current over its lifetime.
The current measurement described above yields a result of the instantaneous current measured at the
31.25 ms measurement times. This value is then used to increment or decrement the ICA register,
increment the CCA (if current is positive), or increment the DCA (if current is negative).
CURRENT
BATTERY
+2.495C
+2.002C
+1.001C
-1.001C
-2.002C
-2.500C
+1.25C
-1.25C
0C
DIGITAL OUTPUT (Binary)
0000 0001 1111 1111
0000 0001 1001 1010
0000 0001 0000 0000
0000 0000 1100 1101
0000 0000 0000 0000
1111 1111 0011 0011
1111 1111 0000 0000
1111 1110 0110 0110
1111 1110 0000 0000
10
corresponds to a current level of 1C. Thus, the range of
6 of 31
DIGITAL OUTPUT (Hex)
00CDh
019Ah
FE66h
FE00h
01FFh
FF33h
FF00h
0100h
0000h
DS2437
SENS