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參數(shù)資料
| 型號： | MAX1894-MAX1924 |
| 廠商： | Maxim Integrated Products, Inc. |
| 元件分類： | 數(shù)字信號處理 |
| 英文描述： | Fixed-Point Digital Signal Processor 288-FCBGA |
| 中文描述： | 先進的鋰電池，包保護器 |
| 文件頁數(shù)： | 7/16頁 |
| 文件大?。?/td> | 308K |
| 代理商： | MAX1894-MAX1924 |
M
Advanced Li+ Battery-Pack Protectors
_______________________________________________________________________________________
7
Detailed Description
The MAX1894/MAX1924 battery-pack protectors super-
vise the charging and discharging process of Li+ cells.
Designed for 3-series (MAX1924V) and 4-series
(MAX1894X/MAX1924X) applications, these devices
monitor the voltage across each cell to provide protec-
tion against undervoltage, overvoltage, and
overcurrent damage.
Output pins
CGO
,
TKO
, and
DSO
control external
MOSFET gates. These MOSFETs, in turn, control the
fast-charging, trickle-charging, and discharge process-
es of the battery pack (Figure 1).
Modes of Operation
Shutdown Mode
The MAX1894/MAX1924 go into shutdown mode under
two conditions: the SHDN pin is driven high without a
charger applied, or a battery cell undervoltage fault is
detected, also without a charger applied. In shutdown
mode, the device consumes 0.8μA (typ) on the V
CC
pin
and all MOSFETs are off. The MAX1894/MAX1924 stay
in shutdown mode as long as no charging voltage is
applied to the battery pack (V
SRC
is less than the pack
voltage). When the battery pack is connected to a
charger (V
SRC
> V
B4P
+ 0.1V) and the pack voltage is
above 4.5V, the device goes into normal operating
mode and begins monitoring the pack (see Figure 2).
Normal Mode
In the normal mode of operation, the MAX1894/MAX1924
are in either a standby mode (29μA typ) or sample mode
(160μA typ). The device enters the standby mode from
shutdown mode. The standby mode lasts for 79ms; then
the device goes into the sample mode. During sample
mode, the MAX1894/MAX1924 check each cell for over-
voltage and undervoltage. Sample mode lasts for 0.5ms;
then the MAX1894/MAX1924 return to standby mode.
During sample mode, the MAX1894/MAX1924 do not intro-
duce cell mismatch.
During normal mode operation, the MAX1894/MAX1924
continuously monitor the voltage across R
SENSE
for charge
or discharge current faults, or battery pack-short faults.
Protection Features
Overvoltage Protection
The MAX1894/MAX1924 provide overvoltage protection
to avoid overcharging cells. When an overvoltage fault
is detected in four consecutive samples,
CGO
and
TKO
go high, stopping the charging process. The
MAX1894/MAX1924 continue to sample the cell volt-
ages, and if no overvoltage is detected,
CGO
and
TKO
are returned to the normal low state (see Figure 3). The
MAX1924 also includes a hysteresis of 200mV.
The overvoltage threshold is preprogrammed and
requires no external components. The overvoltage thresh-
old is factory set at 4.25V (typ) for the MAX1894 and
4.35V (typ) for the MAX1924. Contact Maxim for more
information on threshold levels between 4V and 4.4V.
Undervoltage Protection
The MAX1894/MAX1924 provide undervoltage protec-
tion to avoid overdischarging the cells. With no battery
charger present, and an undervoltage fault is detected
in four consecutive samples,
DSO
,
CGO
, and
TKO
go
high and the device goes into shutdown mode (see
Figure 4).
If a battery charger is applied to the battery pack and
one or more cells are below V
UV_TH
, then only
TKO
goes low, allowing trickle-charge current to flow. If no
undervoltage is detected in any sample,
DSO
,
CGO
,
and
TKO
all go low.
The undervoltage threshold is preprogrammed at 2.30V
(typ). Contact Maxim for more information on threshold
levels between 2V and 3.2V.
Charge-Current Fault Protection
The MAX1894/MAX1924 protect against excessive
charge current by monitoring the voltage developed
across R
SENSE
. R
SENSE
is connected between BN and
PKN. If V
RSENSE
exceeds the charge-current fault
threshold (V
OC_TH
, typically 100mV) for more than 3ms,
the charge current comparator is tripped, setting
CGO
and
TKO
high.
The charge-current fault condition is latched and is not
reset until the MAX1894/MAX1924 detect a reversal in
SYMBOL
DESCRIPTION
V
OC_TH
Charge-Current Fault Threshold
(Negative Value)
Discharge-Current Fault Threshold
V
OD_TH
V
PS_TH
Pack-Short Discharge-Current Fault
Threshold
V
UV_TH
V
OV_TH
V
SRC
V
RSENSE
V
OV_HYT
OVF
UVF
Undervoltage Threshold
Overvoltage Threshold
MOSFET Common Source Voltage
Sense Resistor Voltage
Overvoltage Threshold Hysteresis
Overvoltage Sample Counter
Undervoltage Sample Counter
Table 1. Flow Chart Symbol Table
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| MAX1895EGI-T | 功能描述:顯示驅(qū)動器和控制器 RoHS:否 制造商:Panasonic Electronic Components 工作電源電壓:2.7 V to 5.5 V 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-44 封裝:Reel |
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