參數(shù)資料
型號(hào)： MAX1845ETX
廠商： MAXIM INTEGRATED PRODUCTS INC
元件分類： 穩(wěn)壓器
英文描述： Dual, High-Efficiency, Step-Down Controller with Accurate Current Limit
中文描述： DUAL SWITCHING CONTROLLER, 620 kHz SWITCHING FREQ-MAX, QCC36
封裝： 6 X 6 MM, 0.80 MM, MO220WJJD-1, TQFN-36
文件頁(yè)數(shù)： 11/27頁(yè)
文件大?。?/td> 543K
代理商： MAX1845ETX
M
Dual, High-Efficiency, Step-Down
Controller with Accurate Current Limit
______________________________________________________________________________________
11
time is determined solely by a one-shot whose pulse
width is inversely proportional to input voltage and
directly proportional to output voltage. Another one-shot
sets a minimum off-time (400ns typ). The on-time one-
shot is triggered if the error comparator is low, the low-
side switch current is below the current-limit threshold,
and the minimum off-time one-shot has timed out
(Table 3).
On-Time One-Shot (TON)
The heart of the PWM core is the one-shot that sets the
high-side switch on-time for both controllers. This fast,
low-jitter, adjustable one-shot includes circuitry that
varies the on-time in response to battery and output
voltage. The high-side switch on-time is inversely pro-
portional to the battery voltage as measured by the V+
input, and proportional to the output voltage. This algo-
rithm results in a nearly constant switching frequency
despite the lack of a fixed-frequency clock generator.
The benefits of a constant switching frequency are
twofold: First, the frequency can be selected to avoid
noise-sensitive regions such as the 455kHz IF band;
second, the inductor ripple-current operating point
remains relatively constant, resulting in easy design
methodology and predictable output voltage ripple.
The on-times for side 1 are set 35% higher than the on-
times for side 2. This is done to prevent audio-frequen-
cy
“
beating
”
between the two sides, which switch
asynchronously for each side. The on-time is given by:
On-Time = K (V
OUT
+ 0.075V) / V
IN
where K is set by the TON pin-strap connection (Table
4), and 0.075V is an approximation to accommodate
for the expected drop across the low-side MOSFET
switch. One-shot timing error increases for the shorter
on-time settings due to fixed propagation delays; it is
approximately ±12.5% at higher frequencies and ±10%
at lower frequencies. This translates to reduced switch-
ing-frequency accuracy at higher frequencies (Table
4). Switching frequency increases as a function of load
current due to the increasing drop across the low-side
MOSFET, which causes a faster inductor-current dis-
charge ramp. The on-times guaranteed in the
Electrical
Characteristics
tables are influenced by switching
delays in the external high-side power MOSFET.
V
DD
= 5V
BIAS SUPPLY
POWER-GOOD
INDICATOR
MAX1845EEI
V
CC
OUTPUT1
1.8V, 8A
V
7V TO 24V
D3
CMPSH-3A
ILIM1
ILIM2
DL1
TON
CS1
OUT1
GND
C3
3
470
μ
F
C4
470
μ
F
D1
Q4
Q3
Q1
Q2
LX1
DH1
C5
0.1
μ
F
C6
0.1
μ
F
C7
0.22
μ
F
FB1
V
DD
UVP
C8
1
μ
F
C1
3
10
μ
F
C2
2
10
μ
F
11
12
8
19
18
17
20
16
15
6
14
7
22
25
26
27
24
5
10
2
23
21
9
C11
1
μ
F
L1
2.2
μ
H
L2
4.7
μ
H
13
3
28
1
BST1
REF
ON1
ON2
OVP
DL2
CS2
5V
100k
OUT2
LX2
DH2
FB2
PGOOD
V+
4
BST2
SKIP
C9
4.7
μ
F
R1
20
R1
5m
OUTPUT2
2.5V, 4A
R2
10m
D2
ON/OFF
CONTROLS
Figure 1. Standard Application Circuit
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX1845ETX+ 功能描述:電流型 PWM 控制器 Step-Down Controller RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
MAX1845ETX+T 功能描述:電流型 PWM 控制器 Step-Down Controller RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
MAX1845ETX-T 功能描述:電流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
MAX1845ETX-TG068 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述:
MAX1845EVKIT 功能描述:電源管理IC開發(fā)工具 Evaluation Kit for the MAX1845 RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評(píng)估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V
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