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參數(shù)資料
| 型號： | MAX1874 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | MAX1874 Evaluation Kit |
| 中文描述： | USB/AC適配器雙路輸入、1節(jié)Li+電池充電器，帶OVP與溫度調(diào)節(jié) |
| 文件頁數(shù)： | 12/16頁 |
| 文件大?。?/td> | 405K |
| 代理商： | MAX1874 |
M
The MAX1874
’
s thin QFN package includes a bottom
metal plate that reduces thermal resistance between the
die and the PC board. The external pad should be sol-
dered to a large ground plane. This helps dissipate
power and keeps the die temperature below the thermal
limit. The MAX1874 thermal resistance from the die to the
package thermal pad is typically 5
°
C/W. The thermal
resistance of 1in
2
of 1oz copper on typical FR4 PC board
material in free air is +42
°
C/W (typ). Consequently, the
PC board pad area dominates the MAX1874
’
s ability to
dissipate heat. The MAX1874
’
s thermal regulator is set
for a +105
°
C die temperature. With the example thermal
resistance of +47
°
C/W, the MAX1874 charge-current
thermal limiting can be expected to occur when dissipat-
ing approximately 1.7W at +25
°
C ambient, and when
dissipating approximately 0.75W at +70
°
C ambient.
The power dissipated in the charger is P
DISS
= [V
IN
(either V
USB
or V
DCLV
) - V
BATT
]
I
CHARGE
. Power dis-
sipation drops as the battery voltage rises, so thermal-
charge current limiting, if it occurs, typically releases
soon after charging begins and has little impact on
charge time.
External Thermistor Monitor (THRM)
The MAX1874 features an internal window comparator to
monitor battery pack temperature or ambient tempera-
ture with an external negative temperature coefficient
thermistor. In typical systems, temperature is monitored
to prevent charging at ambient temperature extremes
(below 0
°
C or above +50
°
C). When the temperature
moves outside these limits, charging is stopped. If the
V
THERM
returns to within its normal window, charging
resumes. Connect THRM to GND when not using this
feature. The THRM block diagram is detailed in Figure 1.
Note that the temperature monitor at THRM is entirely
separate from the on-chip temperature limiting dis-
cussed in the
Package Thermal Limiting
section.
The input thresholds for the THRM input are 0.74
V
REF
for the COLD trip point and 0.29
V
REF
for the
HOT trip point.
Applications Information
Input Overvoltage Protection Switch
The DCLV input from an AC adapter or other source
can be protected against overvoltage of up to 18V by
connecting an external P-channel MOSFET (Q2 in
Figures 3, 4, and 5) between DC and DCLV. When V
DC
exceeds 6.2V, the
DCOK
output turns the P-channel
MOSFET off. On power-up,
DCOK
remains high until it
has been verified that V
DC
is in range. If protection
above 6.5V is not needed, then the MOSFET from the
DC to DCLV can be omitted (Figure 2).
Battery-Load Switch
When input power is connected to the charger, some
systems prefer that the battery is disconnected from the
load and that system load current is taken directly from
the DC input or USB source. This is an alternative to the
basic case where the system load is permanently con-
nected to the battery. The later setup is lower cost but
has the disadvantage that if the battery is completely
discharged, the system might not be ready to operate
immediately, or might have limited functionality immedi-
ately upon plugging in the charger. If the battery has a
load-disconnect switch, the system is more complex,
but operation does not depend on the state of the bat-
tery. When system power is taken from the DC or USB
input source, use D1, D2, Q1, and Q2 (Figure 4).
A partial approach to battery-load switching can con-
nect the AC power adapter (DC) directly to the load, but
not USB power (Figure 5). This can be useful when USB
power is insufficient to fully power the system and
charge the battery. When DC is powered, D2 provides a
direct connection to the system and Q3 disconnects the
battery. The battery does not power the load while it is
charging. When only USB is connected, there is no
bypass path from USB to the system. The battery is
charged from the BATT output, and any system power is
drawn from the battery through D5. If the system load
exceeds the current supplied by the charger from USB
(500mA or 100mA), then the battery can still discharge.
In addition, if the system load does not allow the BATT
current to fall below the USB battery full current thresh-
old listed in Table 2, then
CHG
does not go high to indi-
cate a full battery.
Dual-Input, USB/AC Adapter, 1-Cell
Li+ Charger with OVP and Thermal Regulation
12
______________________________________________________________________________________
0.1
μ
F
10k
THERMISTOR
10K
AT +25
°
C
REF
THRM
T
COLD
T
HOT
100mV
TO REGULATOR
Figure 1. Thermistor Sensing Block Diagram
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MAX1874ETE | Dual-Input, USB/AC Adapter, 1-Cell Li+ Charger with OVP and Thermal Regulation |
| MAX1874EVKIT | MAX1874 Evaluation Kit |
| MAX1875 | Dual 180∑ Out-of-Phase PWM Step- Down Controllers with POR |
| MAX1875-MAX1876 | Dual 180∑ Out-of-Phase PWM Step- Down Controllers with POR |
| MAX1875AEEG | Dual 180∑ Out-of-Phase Buck Controllers with Sequencing/Prebias Startup and POR |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX1874ETE | 功能描述:電池管理 Dual-Input USB/AC Adapter 1-Cell Li+ RoHS:否 制造商:Texas Instruments 電池類型:Li-Ion 輸出電壓:5 V 輸出電流:4.5 A 工作電源電壓:3.9 V to 17 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:VQFN-24 封裝:Reel |
| MAX1874ETE+ | 功能描述:電池管理 Dual-Input USB/AC Adapter 1-Cell Li+ RoHS:否 制造商:Texas Instruments 電池類型:Li-Ion 輸出電壓:5 V 輸出電流:4.5 A 工作電源電壓:3.9 V to 17 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:VQFN-24 封裝:Reel |
| MAX1874ETE+T | 功能描述:電池管理 Dual-Input USB/AC Adapter 1-Cell Li+ RoHS:否 制造商:Texas Instruments 電池類型:Li-Ion 輸出電壓:5 V 輸出電流:4.5 A 工作電源電壓:3.9 V to 17 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:VQFN-24 封裝:Reel |
| MAX1874ETE-T | 功能描述:電池管理 Dual-Input USB/AC Adapter 1-Cell Li+ RoHS:否 制造商:Texas Instruments 電池類型:Li-Ion 輸出電壓:5 V 輸出電流:4.5 A 工作電源電壓:3.9 V to 17 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:VQFN-24 封裝:Reel |
| MAX1874EVKIT | 功能描述:電池管理 Evaluation Kit for the MAX1874 RoHS:否 制造商:Texas Instruments 電池類型:Li-Ion 輸出電壓:5 V 輸出電流:4.5 A 工作電源電壓:3.9 V to 17 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:VQFN-24 封裝:Reel |
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