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参数资料
| 型号： | MAX1925 |
| 厂商： | Maxim Integrated Products, Inc. |
| 元件分类： | 数字信号处理 |
| 英文描述： | Fixed-Point Digital Signal Processor 548-FCBGA |
| 中文描述： | 开关模式单节Li+电池充电器 |
| 文件页数： | 14/16页 |
| 文件大小： | 443K |
| 代理商： | MAX1925 |
mode. To ensure stable transition from CCM to CVM
choose a capacitor with the following ESR:
where V
VHIST
is the voltage hysteresis (15mV typ) and
V
IHIST
is the current-sense threshold hysteresis (typi-
cally 30mV). Tantalum capacitors are recommended.
However a ceramic capacitor (typically 10μF) with a
series resistor can also be used.
MOSFET Selection
The MAX1925/MAX1926 drive an external P-channel
MOSFET
’
s gate from IN to GND. Choose a P-channel
MOSFET with a |V
DS,MAX
| > V
IN
. Since EXT drives from
rail to rail the MOSFET must also be rated for |V
GS,MAX
|
> V
IN
. At the lower operating frequencies and currents
for typical MAX1925/MAX1926 applications resistive
and diode losses dominate switching losses. For this
reason choose a MOSFET with a low R
DSON
. The resis-
tive losses are:
P
Resistive_losses
D
I
CHG
2
R
DSON
+ I
CHG
2
(R
SET
+ R
L
)
where D is the operating duty cycle (V
OUT
/V
IN
) and R
L
is the inductor resistance. The MOSFET
’
s power dissi-
pation must exceed D
I
CHG
2
R
DSON
.
Diode Selection
In the event of a short-circuited source, the body diode
inherent in the external PFET allows the cell to dis-
charge. To prevent this and to protect against negative
input voltages, add a Schottky or silicon diode between
the power source and IN.
The MAX1925/MAX1926 use a diode for catching the
inductor current during the off cycle. Select a Schottky
diode with a current rating greater than V
IPK
/R
SET
and
a voltage rating greater than V
IN
.
Dropout Behavior
The MAX1925/MAX1926 regulate charging current by
ramping inductor current between upper and lower
thresholds, typically 128mV and 158mV across R
SET
.
This results in an average current of 142mV/R
SET
. At
input voltages near dropout (4.6V at IN for the typical
circuit), the inductor current ramp waveform becomes
somewhat flattened as inductor, MOSFET, input diode,
and battery resistance limit inductor current. When the
inductor current waveform flattens, it
’
s average value
rises with respect to the upper and lower current
thresholds. This creates a slight peak (about 5%) in
charging current at high battery voltages as seen in the
Charging Current vs. Battery Voltage plot in the
Typical
Operating Characteristics
. Charging current is still con-
trolled in dropout and the charger operates normally.
The dropout current peak can be minimized by reduc-
ing MOSFET and inductor resistance, as well as for-
ward voltage in the input diode.
Thermistor Interface
An external thermistor inhibits charging by setting a
fault flag when the cell is cold (<0
°
C) or hot (>+50
°
C).
The THRM time-multiplexes two sense currents to test
for both hot and cold qualification. Connect the thermis-
tor between THRM and GND. If no temperature qualifi-
cation is desired, replace the thermistor with a 10k
resistor connected through the battery-latch mecha-
nism. The thermistor should be 10k
at +25
°
C and
have a negative temperature coefficient, as defined by
the expression below:
Table 3 shows nominal fault detection temperatures
that result from a wide range of available thermistor
temperature curves.
For a given thermistor characteristic, it is possible to
adjust the fault-detection temperatures by adding a
resistor in series with the thermistor or a parallel resistor
from THRM to GND.
Chip Information
TRANSISTOR COUNT: 5722
PROCESS: BiCMOS
R
R
T
T
C
e
=
+
°
×
25
1
273
1
298
β
R
V
V
R
ESR
VHIST
IHIST
SET
>
×
THERMISTOR BETA
3000
10000
4587.78
25140.55
55.14
°
C
-3.24
°
C
3250
10000
4299.35
27148.09
52.60
°
C
-1.26
°
C
3500
10000
4029.06
29315.94
50.46
°
C
0.46
°
C
3750
10000
3775.75
31656.90
48.63
°
C
1.97
°
C
Resistance at +25
°
C
Resistance at +50
°
C
Resistance at 0
°
C
Nominal Hot Trip Temperature
Nominal Cold Trip Temperature
M
Switch-Mode 1-Cell Li+ Chargers
14
______________________________________________________________________________________
Table 3. Fault Temperature for Different Thermistors
相关PDF资料 |
PDF描述 |
|---|---|
| MAX1926 | Switch-Mode 1-Cell Li+ Chargers |
| MAX1926ETC | Switch-Mode 1-Cell Li+ Chargers |
| MAX1925ETC | Switch-Mode 1-Cell Li+ Chargers |
| MAX192AMJP | Low-Power, 8-Channel, Serial 10-Bit ADC |
| MAX192AEAP | Low-Power, 8-Channel, Serial 10-Bit ADC |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1925ETC | 功能描述:电池管理 Switch-Mode 1-Cell Li+ Charger RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
| MAX1925ETC+ | 功能描述:电池管理 Switch-Mode 1-Cell Li+ Charger RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
| MAX1925ETC+T | 功能描述:电池管理 Switch-Mode 1-Cell Li+ Charger RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
| MAX1925ETC-T | 功能描述:电池管理 Switch-Mode 1-Cell Li+ Charger RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
| MAX1926ETC | 功能描述:电池管理 Switch-Mode 1-Cell Li+ Charger RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
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