参数资料
| 型号： | PS700T-I/ST |
| 厂商： | Microchip Technology |
| 文件页数： | 7/38页 |
| 文件大小： | 0K |
| 描述： | IC BATT MONITOR 1-2CELL 8TSSOP |
| 标准包装： | 1 |
| 功能： | 电池监控器 |
| 电池化学： | 锂离子（Li-Ion） |
| 电源电压： | 2.7 V ~ 9 V |
| 工作温度： | -20°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-TSSOP（0.173"，4.40mm 宽） |
| 供应商设备封装： | 8-TSSOP |
| 包装： | 剪切带 (CT) |
| 其它名称： | PS700T-I/STCT |
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PS700
3.1.4.2
External Temperature
TABLE 3-5:
ACCUMULATOR REGISTERS
For temperature measurement using an external sensor,
the NTC pin supplies a constant current source of
12.5 μ A. For proper operation, an industry standard
10 kOhm at 25°C negative temperature coefficient
(NTC) device of the 103ETBtype, should be connected
between NTC and GND. The NTC reference output is
only enabled during an external temperature
measurement in order to minimize power consumption.
Abbr.
DCA
CCA
TA
VC2A
Accumulator Name
Discharge Current
Accumulator
Charge Current
Accumulator
Temperature Accumulator
VC2 Accumulator
Source
Ires (Sign bit = 1 )
Ires (Sign bit = 0 )
ITres or ETres
VC2res
The output of the current source, connected to the
external thermistor, produces a voltage range with
limits that correspond to operating temperature limits,
as follows:
-20°C → 263 mV
+70°C → 317 mV
The output voltage of the external sensor as a function
The resolution of the accumulated value is equal to the
resolution selected for the associated conversion, up to
a converter resolution of 15-bit plus sign. If a 15-bit plus
sign A/D value is being accumulated, then the
accumulator resolution in microvolt seconds is:
Accumulator LSB ( μ Vs) = (Full Scale Range/# of steps)
* 0.5s = (340 mV/2 15 ) * 0.5s = 5.19 μ Vs
of temperature can be given as:
3.1.7
CHARGE/DISCHARGE
V EX (mV) = 263 + 0.6 * (T + 20)
Defined within the ETctrl registers are the settings for the
reference utilized and the resolution desired for mea-
surement of temperature using the external temperature
sensor. Again, the 340 mV reference should be
selected. The following temperature results in a 10-bit
conversion:
LSB (Voltage) = Full Scale Range/# of steps
= 340 mV/2 10 = 332 μ V/LSB
LSB (°C) = 332 μ V/LSB * (1/600)°C/ μ V
= 0.553°C/LSB
ACCUMULATORS
The DCA register is intended to accumulate discharge
current and the CCA register is intended to accumulate
charge current. Both use the Ires register as its source.
For this reason, in most applications, current measure-
ment defined in the A/D Control registers should be
programmed to measure current by reading the voltage
across the Sense Resistor pin (SR).
During charging, a negative voltage will exist across
the SR pin to ground. Following a conversion, a
positive voltage measurement results in the sign bit = 0
3.1.5
OFFSET COMPENSATION
in the Ires register. When the sign bit = 0 , the measured
result will be added to the CCA register contents and
The host software can perform offset compensation by
using an offset measurement value read from the
PS700. When the offset calibration is enabled within
the OFFSctrl register, the converter inputs are
internally shorted together and an A/D conversion is
performed at the specified resolution. The offset value
is stored in the OFFSres register.
the sum is returned to CCA.
In this way, the total charge current will be accumulated
in CCA.
Similarly, during discharge, a positive voltage will exist
between the SR pin and ground. In this case, the
conversion will result with sign bit = 1 in the Ires regis-
ter, indicating a negative value or discharge current
3.1.6
ACCUMULATION/TIMING
condition. Under this condition, the DCA register will be
The PS700 incorporates four 32-bit accumulators and
four 32-bit elapsed time counters. The Discharge Current
Accumulator (DCA) and the Charge Current Accumula-
tor (CCA) are intended to record discharge and charge
capacity values. The Discharge Time Counter (DTC) and
the Charge Time Counter (CTC) are intended to maintain
the total discharge time and charge time. Accumulated
charge and discharge values can be used to determine
state of charge of the battery as well as cycle count infor-
mation. With information provided by the elapsed time
counters, average charge and discharge currents over
an extended period of time can be calculated.
Each of the four 32-bit accumulator registers is assigned
a fixed “source” A/D Result register. When the accumu-
lator is enabled, it is updated every 500 ms by adding the
contents of the assigned result register value to the
previous accumulator value. The accumulators are
listed in Table 3-5 with their assigned source registers.
? 2004 Microchip Technology Inc.
updated with the discharge current measured during
that conversion.
The value stored in the DCA or CCA register can be
interpreted as illustrated in the following example.
Using a 16-bit signed conversion for current measure-
ment and a 20 m ? sense resistor, the LSB can be
expressed in units of capacity in micro amp seconds as
follows:
Accumulator LSB ( μ As) = Voltage LSB/R SENSE =
(2.59 μ Vs)/20 m ? = 130 μ As
The “Accum” bit in the Accumctrl register must be
enabled for accumulation to occur in both the CCA and
DCA registers.
DS21760F-page 7
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