參數(shù)資料
型號(hào)： LTC3455
廠商： Linear Technology Corporation
元件分類： 基準(zhǔn)電壓源/電流源
英文描述： Dual DC/DC Converter with USB Power Manager and Li-Ion Battery Charger
中文描述： 雙DC / DC轉(zhuǎn)換器的USB電源管理器和鋰離子電池充電器
文件頁(yè)數(shù)： 18/24頁(yè)
文件大小： 516K
代理商： LTC3455
LTC3455
18
3455f
APPLICATIU
W
U
U
Figure 8. Burst Mode and PWM Mode Waveforms
Soft-Start for each Switcher
Soft-start is accomplished by gradually increasing the
peak inductor current for each switcher. This allows each
output to rise slowly, helping minimize the battery in-rush
current. Figure 9 shows the battery current during startup.
A soft-start cycle occurs whenever each switcher first
turns on, or after a fault condition has occurred (thermal
shutdown or UVLO).
Figure 9. In-Rush Current at Startup
In-Rush Current Limiting
When the LTC3455 is battery-powered, an internal 0.15
PMOS switch connects the battery (V
BAT
pin) to the V
MAX
pin to provide power for both switchers and other internal
circuitry. This PMOS switch is turned off in shutdown, and
the V
MAX
pin discharges to ground, providing output
disconnect for all outputs. At startup, this PMOS must first
charge up any capacitance present on the V
MAX
pin to the
battery voltage. To minimize the in-rush current needed
from the battery, the PMOS switch is current-limited to
900mA and both switchers are disabled while the V
MAX
voltage is ramping up. Once V
MAX
reaches the battery
voltage, the PMOS current-limit increases to 4A and both
switchers are allowed to turn on. Figure 9 shows the
startup battery current for the LTC3455, which stays well-
controlled while V
MAX
is ramping up and while both
switchers outputs are rising.
Battery Charger General Information
The battery charger and Switcher 1 will always be enabled
whenever USB or wall power is present (as sensed by the
USB and WALLFB pins). This ensures that the battery can
be charged and that the microcontroller is alive whenever
external power is available. For some applications, it may
be undesirable for the charger to become active immedi-
ately when external power is applied. For such applica-
tions, an NMOS switch can be used to disconnect the
R
PROG
resistor and allow the PROG pin to float high,
turning off the charger. In this manner, charging occurs
only when allowed by the microcontroller.
The LTC3455 battery charger is a constant-current, con-
stant-voltage charger. In constant-current mode, the maxi-
mum charge current is set by a single external resistor.
When the battery approaches the final float voltage, the
charge current begins to decrease as the charger switches
to constant-voltage mode. The charge cycle is terminated
only by the charge timer.
V
2V/DIV
V
OUT1
(1.8V)
2V/DIV
V
OUT2
(3.3V)
2V/DIV
100
μ
s/DIV
3455 F09
I
500mA/DIV
V
2V/DIV
1
μ
s/DIV
3455 F08b
V
10mV/DIV
AC COUPLED
I
L1
100mA/DIV
V
2V/DIV
V
50mV/DIV
AC COUPLED
5
μ
s/DIV
3455 F08a
I
L1
100mA/DIV
PWM Mode
Burst Mode
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參數(shù)描述
LTC3455EUF 功能描述:IC CONV DC/DC DUAL USBBATT 24QFN RoHS:否 類別:集成電路 (IC) >> PMIC - 電源管理 - 專用 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 應(yīng)用:手持/移動(dòng)設(shè)備 電流 - 電源:- 電源電壓:3 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:14-WFDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:14-LLP-EP（4x4） 包裝:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名稱:LP3905SD-30DKR
LTC3455EUF#PBF 功能描述:IC CONV DC/DC DUAL USBBATT 24QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 電源管理 - 專用 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 應(yīng)用:手持/移動(dòng)設(shè)備 電流 - 電源:- 電源電壓:3 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:14-WFDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:14-LLP-EP（4x4） 包裝:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名稱:LP3905SD-30DKR
LTC3455EUF#TR 功能描述:IC CONV DC/DC DUAL USBBATT 24QFN RoHS:否 類別:集成電路 (IC) >> PMIC - 電源管理 - 專用 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 應(yīng)用:手持/移動(dòng)設(shè)備 電流 - 電源:- 電源電壓:3 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:14-WFDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:14-LLP-EP（4x4） 包裝:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名稱:LP3905SD-30DKR
LTC3455EUF#TRPBF 功能描述:IC CONV DC/DC DUAL USBBATT 24QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 電源管理 - 專用 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 應(yīng)用:手持/移動(dòng)設(shè)備 電流 - 電源:- 電源電壓:3 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:14-WFDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:14-LLP-EP（4x4） 包裝:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名稱:LP3905SD-30DKR
LTC3455EUF-1#PBF 功能描述:IC DC/DC CONV DUAL CHRG 24-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 電源管理 - 專用 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 應(yīng)用:手持/移動(dòng)設(shè)備 電流 - 電源:- 電源電壓:3 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:14-WFDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:14-LLP-EP（4x4） 包裝:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名稱:LP3905SD-30DKR
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