MAX1776EUA+T
更新时间：2024-09-18 13:07:47
品牌：MAXIM
描述：Switching Regulator, Current-mode, 2A, 200kHz Switching Freq-Max, BICMOS, PDSO8, MSOP-8
概述
规格参数
数据手册
替代型号MAX1776EUA+T 概述
Switching Regulator, Current-mode, 2A, 200kHz Switching Freq-Max, BICMOS, PDSO8, MSOP-8 DC/DC转换器 开关式稳压器或控制器
MAX1776EUA+T 规格参数
| 是否无铅： | 不含铅 | 是否Rohs认证： | 符合 |
| 生命周期： | Active | 零件包装代码： | MSOP |
| 包装说明： | TSSOP, TSSOP8,.19 | 针数： | 8 |
| Reach Compliance Code： | compliant | ECCN代码： | EAR99 |
| HTS代码： | 8542.39.00.01 | Factory Lead Time： | 6 weeks |
| 风险等级： | 0.89 | Is Samacsys： | N |
| 模拟集成电路 - 其他类型： | SWITCHING REGULATOR | 控制模式： | CURRENT-MODE |
| 最大输入电压： | 24 V | 最小输入电压： | 4.5 V |
| 标称输入电压： | 12 V | JESD-30 代码： | S-PDSO-G8 |
| JESD-609代码： | e3 | 长度： | 3 mm |
| 湿度敏感等级： | 1 | 功能数量： | 1 |
| 端子数量： | 8 | 最高工作温度： | 85 °C |
| 最低工作温度： | -40 °C | 最大输出电流： | 2 A |
| 封装主体材料： | PLASTIC/EPOXY | 封装代码： | TSSOP |
| 封装等效代码： | TSSOP8,.19 | 封装形状： | SQUARE |
| 封装形式： | SMALL OUTLINE, THIN PROFILE, SHRINK PITCH | 峰值回流温度（摄氏度）： | 260 |
| 认证状态： | Not Qualified | 座面最大高度： | 1.1 mm |
| 子类别： | Switching Regulator or Controllers | 表面贴装： | YES |
| 切换器配置： | BUCK | 最大切换频率： | 200 kHz |
| 技术： | BICMOS | 温度等级： | INDUSTRIAL |
| 端子面层： | Matte Tin (Sn) | 端子形式： | GULL WING |
| 端子节距： | 0.65 mm | 端子位置： | DUAL |
| 处于峰值回流温度下的最长时间： | 30 | 宽度： | 3 mm |
| Base Number Matches： | 1 |
MAX1776EUA+T 数据手册
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PDF下载19-1975; Rev 2; 7/03
24V, 600mA Internal Switch, 100% Duty Cycle,
Step-Down Converter
General Description
Features
The MAX1776 high-efficiency step-down converter pro-
o Fixed 5V or Adjustable Output
o 4.5V to 24V Input Voltage Range
o Up to 600mA Output Current
o Internal 0.4Ω P-Channel MOSFET
o Efficiency Over 95%
vides an adjustable output voltage from 1.25V to V from
IN
supply voltages as high as 24V. An internal current-limit-
ed 0.4Ω MOSFET delivers load currents up to 600mA.
Operation to 100% duty cycle minimizes dropout volt-
age (240mV at 600mA).
The MAX1776 has a low 15µA quiescent current to
improve light-load efficiency and conserve battery life.
The device draws only 3µA while in shutdown.
o 15µA Quiescent Supply Current
o 3µA Shutdown Current
High switching frequencies (up to 200kHz) allow the
use of tiny surface-mount inductors and output capaci-
tors. The MAX1776 is available in an 8-pin µMAX pack-
age, which uses half the space of an 8-pin SO. For
increased output drive capability, use the MAX1626/
MAX1627 step-down controllers, which drive an exter-
nal P-channel MOSFET to deliver up to 20W.
o 100% Maximum Duty Cycle for Low Dropout
o Current-Limited Architecture
o Thermal Shutdown
o Small 8-µMAX Package
Ordering Information
Applications
Notebook Computers
PART
TEMP RANGE
PIN-PACKAGE
Distributed Power Systems
Keep-Alive Supplies
Hand-Held Devices
MAX1776EUA
-40°C to +85°C
8 µMAX
Typical Operating Circuit
Pin Configuration
TOP VIEW
V
IN
IN
SHDN
ILIM
V
OUT
FB
GND
ILIM
LX
1
2
3
4
8
7
6
5
OUT
SHDN
ILIM2
IN
LX
MAX1776
MAX1776EUA
ILIM2
FB
OUT
GND
µMAX
µMAX
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
24V, 600mA Internal Switch, 100% Duty Cycle,
Step-Down Converter
ABSOLUTE MAXIMUM RATINGS
IN, SHDN, ILIM, ILIM2 to GND .................................-0.3V to 25V
Continuous Power Dissipation (T = +70°C)
A
8-Pin µMAX (derate 4.1mW/°C above +70°C).............330mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
LX to GND.......................................................-2V to (V + 0.3V)
IN
OUT, FB to GND .........................................................-0.3V to 6V
Peak Input Current .................................................................. 2A
Maximum DC Input Current.............................................. 500mA
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V = +12V, SHDN = IN, T = 0°C to +85°C, unless otherwise noted.)
IN
A
PARAMETER
Input Voltage Range
SYMBOL
CONDITIONS
MIN
TYP
MAX
24
UNITS
V
V
4.5
IN
IN
Input Supply Current
I
No load
15
50
28
µA
Input Supply Current in Dropout
Input Shutdown Current
I
No load
70
µA
IN(DROP)
SHDN = GND
3
7
µA
V
V
rising
falling
3.6
3.5
4.0
3.9
5.00
4.4
4.3
5.20
IN
IN
Input Undervoltage Lockout
Threshold
V
V
UVLO
Output Voltage (Preset Mode)
V
FB = GND
4.80
V
V
OUT
Feedback Set Voltage
(Adjustable Mode)
V
1.212
1.65
1.25
3.5
1.288
FB
OUT Bias Current
V
V
= 5.5V
6.25
5.5
µA
V
OUT
OUT Pin Maximum Voltage
FB Bias Current
I
= 1.3V
= 1.3V
-25
50
+25
150
0.62
12
nA
mV
µs
µs
FB
FB
FB
FB Dual Mode™ Threshold Low
LX Switch Minimum Off-Time
LX Switch Maximum On-Time
100
0.42
10
t
0.22
8
OFF(MIN)
t
V
ON(MAX)
ILIM = ILIM2 = GND
ILIM = GND, ILIM2 = IN
ILIM = IN, ILIM2 = GND
ILIM = ILIM2 = IN
1.6
3.2
0.8
1.6
V
= 6V
IN
0.4
0.8
0.4
0.8
LX Switch On-Resistance
R
Ω
LX
ILIM = ILIM2 = GND
ILIM = GND, ILIM2 = IN
ILIM = IN, ILIM2 = GND
ILIM = ILIM2 = IN
1.9
3.8
1.0
1.9
V
= 4.5V
IN
0.5
0.95
0.95
180
360
720
1440
+75
0.5
ILIM = ILIM2 = GND
ILIM = GND, ILIM2 = IN
ILIM = IN, ILIM2 = GND
ILIM = ILIM2 = IN
120
240
480
960
-75
150
300
600
1200
LX Current Limit
I
mA
LX(PEAK)
LX Zero-Crossing Threshold
Zero-Crossing Timeout
mV
µs
LX does not rise above the threshold
30
T
A
T
A
= +25°C
1
V
= 24V,
IN
LX Switch Leakage Current
µA
LX = GND
= 0°C to +85°C
10
Dual Mode is a trademark of Maxim Integrated Products, Inc.
2
_______________________________________________________________________________________
24V, 600mA Internal Switch, 100% Duty Cycle,
Step-Down Converter
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V = +12V, SHDN = IN, T = 0°C to +85°C, unless otherwise noted.)
IN
A
PARAMETER
SYMBOL
CONDITIONS
= 525mA, ILIM = ILIM2 = IN
= 8V/24V, 200Ω load
MIN
TYP
0.2
MAX
UNITS
V
Dropout Voltage
V
I
DROPOUT OUT
Line Regulation
Load Regulation
V
0.1
%/V
%
IN
No load/full load
0.9
Low
0.8
Digital Input Level
SHDN, ILIM2
V
µA
V
High
2.4
-1
Digital Input Leakage Current
ILIM Input Level
V
, V
, V
= 0 or 24V, V = 24V
+1
SHDN ILIM ILIM2
IN
Low
0.05
High
2.2
Thermal Shutdown
10°C hysteresis
160
°C
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V = +12V, SHDN = IN, T = -40°C to +85°C, unless otherwise noted.) (Note 1)
IN
A
PARAMETER
Input Voltage Range
SYMBOL
CONDITIONS
MIN
MAX
24
UNITS
V
V
4.5
IN
IN
Input Supply Current
I
No load
28
µA
Input Supply Current in Dropout
Input Shutdown Current
I
No load
70
µA
IN(DROP)
SHDN = GND
7
µA
V
V
rising
falling
3.6
3.5
4.4
4.3
5.25
IN
IN
Input Undervoltage Lockout
Threshold
V
V
V
V
UVLO
Output Voltage (Preset Mode)
V
FB = GND
4.75
OUT
Feedback Set Voltage
(Adjustable Mode)
V
1.2
1.3
FB
OUT Bias Current
V
V
= 5.5V
1.65
6.25
5.5
µA
V
OUT
OUT Pin Maximum Voltage
FB Bias Current
I
= 1.3V
= 1.3V
-25
45
+25
155
0.64
12.5
3.2
nA
mV
µs
µs
FB
FB
FB
FB Dual Mode Threshold Low
LX Switch Minimum Off-Time
LX Switch Maximum On-Time
t
0.22
7.5
OFF(MIN)
t
V
ON(MAX)
ILIM = ILIM2 = GND
ILIM = GND, ILIM2 = IN
ILIM = IN, ILIM2 = GND
ILIM = ILIM2 = IN
1.6
V
= 6V
IN
0.8
0.8
LX Switch On-Resistance
R
Ω
LX
ILIM = ILIM2 = GND
ILIM = GND, ILIM2 = IN
ILIM = IN, ILIM2 = GND
ILIM = ILIM2 = IN
3.8
1.9
V
= 4.5V
IN
0.95
0.95
200
400
800
1600
ILIM = ILIM2 = GND
ILIM = GND, ILIM2 = IN
ILIM = IN, ILIM2 = GND
ILIM = ILIM2 = IN
100
200
400
800
LX Current Limit
I
mA
LX(PEAK)
_______________________________________________________________________________________
3
24V, 600mA Internal Switch, 100% Duty Cycle,
Step-Down Converter
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V = +12V, SHDN = IN, T = -40°C to +85°C, unless otherwise noted.) (Note 1)
IN
A
PARAMETER
SYMBOL
CONDITIONS
MIN
MAX
75
UNITS
mV
LX Zero-Crossing Threshold
LX Switch Leakage Current
-75
V
= 24V, LX = GND
10
µA
IN
Low
0.8
Digital Input Level
SHDN, ILIM2
, V
V
µA
V
High
2.4
-1
Digital Input Leakage Current
ILIM Input Level
V
, V
= 0 or 24V, V = 24V
1
SHDN ILIM ILIM2
IN
Low
0.05
High
2.2
Note 1: Specifications to -40°C are guaranteed by design, not production tested.
Typical Operating Characteristics
(Circuit of Figure 1, components from Table 3, V = +12V, SHDN = IN, T = +25°C.)
IN
A
LOAD REGULATION,
LOAD REGULATION,
CIRCUIT 1, V = 5V
LOAD REGULATION, CIRCUIT 2
CIRCUIT 1, V
= 3.3V
OUTPUT
OUTPUT
0.6
0.2
0
0.2
0
V
IN
= 5V
0.4
0.2
-0.2
-0.4
-0.6
-0.8
-1.0
-1.2
-0.2
-0.4
-0.6
-0.8
-1.0
-1.2
V = 24V
IN
V
IN
= 12V
0
-0.2
-0.4
-0.6
-0.8
-1.0
V
IN
= 15V
V
IN
= 24V
V
IN
= 12V
100
V
IN
= 12V
V
V
IN
= 24V
= 15V
IN
V
IN
= 15V
0
200
300
(mA)
400
500
600
0
100 200 300 400 500 600 700
(mA)
0
50 100 150 200 250 300 350 400
(mA)
I
I
LOAD
I
LOAD
LOAD
V
vs. V ,
IN
V
OUTPUT
LOAD REGULATION, CIRCUIT 5
CIRCUIT 5, V
= 5V
CIRCUIT 5, V
OUTPUT
0
-0.1
-0.2
-0.3
-0.4
-0.5
-0.6
-0.7
-0.8
-0.9
1.0
3
2.0
1.5
1.0
0.5
0
V
= 12V
IN
2
1
V
IN
= 24V
I
= 1mA
LOAD
I
= 50mA
LOAD
I
= 1mA
LOAD
0
I
= 10mA
LOAD
I
= 500mA
LOAD
-1
-2
-3
V
= 15V
IN
-0.5
-1.0
I
= 50mA
LOAD
5
7
9
11 13 15 17 19 21 23 25
(V)
5
7
9
11 13 15 17 19 21 23 25
(V)
0
0.1
0.2
0.3
0.4
0.5
0.6
V
IN
V
IN
I
(A)
LOAD
4
_______________________________________________________________________________________
24V, 600mA Internal Switch, 100% Duty Cycle,
Step-Down Converter
Typical Operating Characteristics (continued)
(Circuit of Figure 1, components from Table 3, V = +12V, SHDN = IN, T = +25°C.)
IN
A
V
vs. V ,
IN
V
vs. V ,
EFFICIENCY vs. I
, CIRCUIT 1,
LOAD
= 5V
OUTPUT
OUTPUT
IN
V
CIRCUIT 1, V
= 5V
CIRCUIT 1, V
= 3.3V
OUT
OUTPUT
OUTPUT
0.6
0.4
0.2
0
100
0.4
0.2
V
IN
= 6V
I
= 10mA
LOAD
95
90
85
80
75
70
65
60
I
= 1mA
LOAD
I
= 1mA
LOAD
I
= 10mA
LOAD
V
IN
= 12V
0
V
IN
= 24V
V
IN
= 15V
-0.2
-0.4
-0.6
-0.8
1.0
-0.2
-0.4
-0.6
-0.8
-1.0
-1.2
I
= 50mA
LOAD
I
= 50mA
LOAD
I
= 500mA
I
= 500mA
LOAD
LOAD
55
50
5
7
9
11 13 15 17 19 21 23 25
5
0.10
5
7
9
11 13 15 17 19 21 23 25
0.10
1
10
(mA)
100
1000
V
IN
(V)
V
IN
(V)
I
LOAD
EFFICIENCY vs. I
V
, CIRCUIT 5,
EFFICIENCY vs. I
V
, CIRCUIT 1,
LOAD
LOAD
EFFICIENCY vs. V , I
= 500mA
= 3.3V
= 3.3V
IN LOAD
OUTPUT
OUTPUT
100
95
90
85
80
75
70
65
60
55
50
100
100
V
IN
= 6V
95
90
85
80
75
70
65
60
95
90
85
80
75
70
65
60
CIRCUIT 5, 5V
CIRCUIT 1, 5V
V
IN
= 6V
V
IN
= 12V
CIRCUIT 1, 3.3V
V
IN
= 12V
CIRCUIT 5, 3.3V
V
IN
= 24V
V
IN
= 15V
V
IN
= 24V
55
50
55
50
0.10
1
10
(mA)
100
1000
7
8
9
10 11 12 13 14 15 16
(V)
1
10
(mA)
100
1000
I
V
IN
I
LOAD
LOAD
SWITCHING FREQUENCY vs.
LOAD CURRENT, CIRCUIT 1
SWITCHING FREQUENCY vs.
, CIRCUIT 1
V
V
ACCURACY vs. TEMPERATURE
OUTPUT
IN
200
180
160
140
120
100
80
140
120
100
80
1.5
1.0
0.5
0
V
IN
= 15V
I
= 500mA
= 375mA
LOAD
I
LOAD
LOAD
V
= 24V
IN
I
= 250mA
60
I
= 5mA
LOAD
-0.5
-1.0
-1.5
60
40
V
IN
= 12V
I
= 10mA
LOAD
I
= 50mA
LOAD
40
20
20
0
0
0
100 200 300 400 500 600 700 800 900
(mA)
10
15
(V)
20
25
-40 -20
0
20
40
60
80 100
I
V
IN
TEMPERATURE (°C)
LOAD
_______________________________________________________________________________________
5
24V, 600mA Internal Switch, 100% Duty Cycle,
Step-Down Converter
Typical Operating Characteristics (continued)
(Circuit of Figure 1, components from Table 3, V = +12V, SHDN = IN, T = +25°C.)
IN
A
QUIESCENT SUPPLY CURRENT
vs. TEMPERATURE
QUIESCENT SUPPLY CURRENT
vs. SUPPLY VOLTAGE
14.20
18.0
17.5
17.0
16.5
16.0
15.5
15.0
14.15
14.10
14.05
14.00
13.95
13.90
13.85
13.80
13.75
13.70
-40
-20
0
20
40
60
80
5
7
9
11 13 15 17 19 21 23 25
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
PEAK SWITCH CURRENT
vs. INPUT VOLTAGE, CIRCUIT 3, 0.3A
LOAD-TRANSIENT RESPONSE,
CIRCUIT 5
MAX1776 toc19
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
L = 10µH
1A
0
I
L
L = 22µH
10V
V
LX
0
L = 47µH
AC COUPLED
50mV/div
V
OUT
L = 100µH
500mA
I
LOAD
10mA
0
5
10
15
20
25
10µs/div
V
IN
(V)
LINE-TRANSIENT RESPONSE,
CIRCUIT 5, I = 50mA
LINE-TRANSIENT RESPONSE,
CIRCUIT 5, I = 500mA
LOAD
LOAD
MAX1776 toc21
MAX1776 toc20
AC-COUPLED
200mv/div
V
OUT
AC-COUPLED
200mv/div
V
OUT
15V
10V
V
IN
10V
5V
V
IN
10V
5V
0
V
LX
5V
0
V
LX
200µs/div
200µs/div
6
_______________________________________________________________________________________
24V, 600mA Internal Switch, 100% Duty Cycle,
Step-Down Converter
Typical Operating Characteristics (continued)
(Circuit of Figure 1, components from Table 3, V = +12V, SHDN = IN, T = +25°C.)
IN
A
LX WAVEFORM, CIRCUIT 1
STARTUP WAVEFORM, CIRCUIT 1,
= 100Ω
V
= 15V, I
= 500mA
R
LOAD
IN
LOAD
MAX1776 toc22
MAX1776 toc23
5V
0
V
1A
0
SHDN
I
L
1A
0
I
L
10V
0
V
LX
6V
4V
2V
0
V
OUT
V
OUT
50mV/div
2µs/div
2µs/div
EFFICIENCY vs. I
, CIRCUIT 3, V = 12V
IN
EFFICIENCY vs. I
, CIRCUIT 3, V = 12V
IN
LOAD
LOAD
100
95
90
85
80
100
95
90
85
80
L = 22µH
L = 22µH, 0.6A
L = 47µH, 0.3A
L = 47µH
L = 100µH
L = 10µH, 1.2A
75
75
0.10
1
10
(mA)
100
1000
0.10
1
10
(mA)
100
1000
I
I
LOAD
LOAD
_______________________________________________________________________________________
7
24V, 600mA Internal Switch, 100% Duty Cycle,
Step-Down Converter
Pin Description
PIN
NAME
FUNCTION
Dual-Mode Feedback Input. Connect to GND for the preset 5V output. Connect to a resistive divider
1
2
3
FB
between OUT and GND to adjust the output voltage between 1.25V and V
.
IN
GND
ILIM
Ground
Peak Current Control Input. Connect to IN or GND to set peak current limit. ILIM and ILIM2 together set
the peak current limit. See Setting Current Limit.
4
5
LX
IN
Inductor Connection. Connect LX to external inductor and diode as shown in Figure 1.
Input Supply Voltage. Input voltage range is 4.5V to 24V.
Peak Current Control Input 2. Connect to IN or GND. ILIM and ILIM2 together set the peak current limit.
See Setting Current Limit.
6
7
8
ILIM2
SHDN
OUT
Shutdown Input. A logic low shuts down the MAX1776 and reduces the supply current to 3µA. LX is high
impedance in shutdown. Connect to IN for normal operation.
Regulated Output Voltage High-Impedance Sense Input. Internally connected to a resistive divider.
Do not connect for output voltages higher than 5.5V. Connect to GND when not used.
Current-Limited Control Architecture
The MAX1776 uses a proprietary current-limited control
Detailed Description
The MAX1776 step-down converter is designed primar-
ily for battery-powered devices and notebook comput-
ers. The unique current-limited control scheme
provides high efficiency over a wide load range.
Operation up to 100% duty cycle allows the lowest pos-
sible dropout voltage, increasing the usable supply
voltage range. Under no load, the MAX1776 draws only
15µA, and in shutdown mode, it draws only 3µA to fur-
ther reduce power consumption and extend battery life.
Additionally, an internal 24V switching MOSFET, inter-
nal current sensing, and a high switching frequency
minimize PC board space and component costs.
scheme with operation to 100% duty cycle. This DC-DC
converter pulses as needed to maintain regulation,
resulting in a variable switching frequency that increas-
es with the load. This eliminates the high supply cur-
rents associated with conventional constant-frequency
pulse-width-modulation (PWM) controllers that switch
the MOSFET unnecessarily.
When the output voltage is too low, the error comparator
sets a flip-flop, which turns on the internal P-channel
MOSFET and begins a switching cycle (Figure 2). As
shown in Figure 3, the inductor current ramps up linear-
ly, storing energy in a magnetic field while charging the
output capacitor and servicing the load. The MOSFET
turns off when the peak current limit is reached, or when
the maximum on-time of 10µs is exceeded and the out-
put voltage is in regulation. If the output is out of regula-
tion and the peak current is never obtained, the
MOSFET remains on, allowing a duty cycle up to 100%.
This feature ensures the lowest possible dropout volt-
age. Once the MOSFET turns off, the flip-flop resets, the
inductor current is pulled through D1, and the current
through the inductor ramps back down, transferring the
stored energy to the output capacitor and load. The
MOSFET remains off until the 0.42µs minimum off-time
expires, and the output voltage drops out of regulation.
OUTPUT
5V
INPUT
4.5V TO 24V
L1
IN
LX
C
IN
D1
C
OUT
SHDN
J1
J2
MAX1776
ILIM
ILIM2
OUT
FB
J3
J4
GND
C : 10µF, 25V CERAMIC
IN
NOTE: HIGH-CURRENT PATHS SHOWN WITH BOLD LINES.
SEE TABLE 3 FOR OTHER COMPONENT VALUES
Figure 1. Typical Application Circuit
8
_______________________________________________________________________________________
24V, 600mA Internal Switch, 100% Duty Cycle,
Step-Down Converter
MAX1776
L1
OUTPUT
D
LX
C
IN
D1
C
OUT
OUT
FB
Q
R
S
SHDN
MAXIMUM
ON-TIME
DELAY
100mV
ILIM
ILIM
SET
V
SET
1.25V
ILIM2
MINIIMUM
OFF-TIME
DELAY
GND
Figure 2. Simplified Functional Diagram
Input-Output (Dropout) Voltage
A step-down converter’s minimum input-to-output volt-
age differential (dropout voltage) determines the lowest
usable supply voltage. In battery-powered systems,
this limits the useful end-of-life battery voltage. To maxi-
mize battery life, the MAX1776 operates with duty
cycles up to 100%, which minimizes the dropout volt-
age and eliminates switching losses while in dropout.
When the supply voltage approaches the output volt-
age, the P-channel MOSFET remains on continuously to
supply the load.
LX WAVEFORM, CIRCUIT 1
V
= 15V, I
= 500mA
IN
LOAD
1A
I
L
0
10V
0
V
LX
Dropout voltage is defined as the difference between
the input and output voltages when the input is low
enough for the output to drop out of regulation. For a
step-down converter with 100% duty cycle, dropout
depends on the MOSFET drain-to-source on-resistance
and inductor series resistance; therefore, it is propor-
tional to the load current:
V
OUT
50mV/div
2µs/div
Figure 3. Discontinuous-Conduction Operation
V
= I
✕ (R
R
)
DROPOUT
OUT
DS(ON) + INDUCTOR
_______________________________________________________________________________________
9
24V, 600mA Internal Switch, 100% Duty Cycle,
Step-Down Converter
SHDN
Shutdown (
)
Table 1. Current-Limit Configuration
A logic low level on SHDN shuts down the MAX1776
converter. When in shutdown, the supply current drops
to 3µA to maximize battery life, and the internal P-chan-
nel MOSFET turns off to isolate the output from the input.
The output capacitance and load current determine the
rate at which the output voltage decays. A logic level
high on SHDN activates the MAX1776. Do not leave
SHDN floating. If unused, connect SHDN to IN.
CURRENT
LIMIT (mA)
ILIM
ILIM2
CONNECTED TO
CONNECTED TO
150
300
GND
GND
IN
GND
IN
600
GND
IN
1200
IN
Thermal-Overload Protection
Thermal-overload protection limits total power dissipa-
tion in the MAX1776. When the junction temperature
Choose a current limit that realistically reflects the maxi-
mum load current. The maximum output current is half
of the peak current limit. Although choosing a lower
current limit allows using an inductor with a lower cur-
rent rating, it requires a higher inductance (see
Inductor Selection) and does little to reduce inductor
package size.
exceeds T = +160°C, a thermal sensor turns off the
J
pass transistor, allowing the IC to cool. The thermal sen-
sor turns the pass transistor on again after the IC’s junc-
tion temperature cools by 10°C, resulting in a pulsed
output during continuous thermal-overload conditions.
Design Information
Inductor Selection
When selecting the inductor, consider these four para-
meters: inductance value, saturation rating, series
resistance, and size. The MAX1776 operates with a
wide range of inductance values. For most applica-
tions, values between 10µH and 100µH work best with
the controller’s high switching frequency. Larger induc-
tor values will reduce the switching frequency and
thereby improve efficiency and EMI. The trade-off for
improved efficiency is a higher output ripple and slower
transient response. On the other hand, low-value induc-
tors respond faster to transients, improve output ripple,
offer smaller physical size, and minimize cost. If the
inductor value is too small, the peak inductor current
exceeds the current limit due to current-sense com-
parator propagation delay, potentially exceeding the
inductor’s current rating. Calculate the minimum induc-
tance value as follows:
Output Voltage Selection
The feedback input features dual-mode operation.
Connect FB to GND for the 5.0V preset output voltage.
Alternatively, adjust the output voltage by connecting a
voltage-divider from the output to GND (Figure 4).
Select a value for R2 between 10kΩ and 100kΩ.
Calculate R1 with the following equation:
V
OUTPUT
R1 = R2 ×
-1
V
FB
where V
= 1.25V, and V
may range from
FB
OUTPUT
1.25V to V .
IN
Setting Current Limit
The MAX1776 has an adjustable peak current limit.
Configure this peak current limit by connecting ILIM
and ILIM2 as shown in Table 1.
VIN(MAX) - V
× t
(
)
OUTPUT
ON(MIN)
L
(MIN) =
I
)
LX (PEAK
where t
= 1µs.
ON(MIN)
OUTPUT
1.25V TO V
INPUT
L1
4.5V TO 24V
IN
The inductor’s saturation current rating must be greater
than the peak switch current limit, plus the overshoot
due to the 250ns current-sense comparator propaga-
tion delay. Saturation occurs when the inductor’s mag-
netic flux density reaches the maximum level the core
can support and the inductance starts to fall. Choose
IN
LX
C
IN
D1
C
OUT
SHDN
ILIM
ILIM2
R1
R2
MAX1776
FB
an inductor with a saturation rating greater than I
in the following equation:
PEAK
GND
OUT
I
= I
+ (V - V
) ✕ 250ns / L
OUTPUT
PEAK
LX(PEAK)
IN
Figure 4. Adjustable Output Voltage
10 ______________________________________________________________________________________
24V, 600mA Internal Switch, 100% Duty Cycle,
Step-Down Converter
Inductor series resistance affects both efficiency and
dropout voltage (see Input-Output (Dropout) Voltage).
High series resistance limits the maximum current avail-
able at lower input voltages, and increases the dropout
voltage. For optimum performance, select an inductor
with the lowest possible DC resistance that fits in the
allotted dimensions. Some recommended component
manufacturers are listed in Table 2.
Input Capacitor
The input filter capacitor reduces peak currents drawn
from the power source and reduces noise and voltage
ripple on the input caused by the circuit’s switching.
The input capacitor must meet the ripple-current
requirement (I
) imposed by the switching current
RMS
defined by the following equation:
I
V
4
3
V
LOAD OUTPUT
IN
V
OUTPUT
Maximum Output Current
The MAX1776 converter’s output current determines
the regulator’s switching frequency. When the convert-
er approaches continuous mode, the output voltage
falls out of regulation. For the typical application, the
maximum output current is approximately:
I
=
×
−1
RMS
V
IN
For most applications, nontantalum chemistries (ceram-
ic, aluminum, polymer, or OS-CON) are preferred due to
their robustness to high inrush currents typical of sys-
tems with low-impedance battery inputs. Alternatively,
connect two (or more) smaller value low-ESR capacitors
in parallel to reduce cost. Choose an input capacitor
that exhibits less than +10°C temperature rise at the
RMS input current for optimal circuit longevity.
I
= 1/2 I
LX (PEAK)(MIN)
LOAD(MAX)
For low-input voltages, the maximum on-time may be
reached and the load current is limited by:
I
= 1/2 (V - V
) ✕ 10µs / L
OUT
LOAD
IN
Output Capacitor
Table 2. Component Suppliers
Choose the output capacitor to service the maximum
load current with acceptable voltage ripple. The output
ripple has two components: variations in the charge
stored in the output capacitor with each LX pulse, and
the voltage drop across the capacitor’s equivalent
series resistance (ESR) caused by the current into and
out of the capacitor:
SUPPLIER
DIODES
WEBSITE
Central Semiconductor
Fairchild
www.centralsemi.com
www.fairchildsemi.com
www.gensemi.com
www.irf.com
General Semiconductor
International Rectifier
V
≅ V
+ V
RIPPLE
RIPPLE(ESR) RIPPLE(C)
The output voltage ripple as a consequence of the ESR
and output capacitance is:
www.niec.co.jp/engver2/
niec.co.jp_eg.htm
Nihon
V
=ESR×I
PEAK
RIPPLE(ESR)
On Semi
www.onsemi.com
2
www.vishay.com/brands/siliconix/
main.html
L × IPEAK -I
(
)
V
OUTPUT
Vishay-Siliconix
IN
V
=
RIPPLE(C)
2C
× V
V -V
IN OUTPUT
OUT
OUTPUT
www.zetex.com
Zetex
where I
is the peak inductor current (see Inductor
CAPACITORS
AVX
PEAK
Selection). The worst-case ripple occurs at no-load.
These equations are suitable for initial capacitor selec-
tion, but final values should be set by testing a proto-
type or evaluation circuit. As a general rule, a smaller
amount of charge delivered in each pulse results in
less output ripple. Since the amount of charge deliv-
ered in each oscillator pulse is determined by the
inductor value and input voltage, the voltage ripple
increases with larger inductance, and as the input volt-
age decreases. See Table 3 for recommended capaci-
tor values and Table 2 for recommended component
manufacturers.
www.avxcorp.com
www.kemet.com
Kemet
Nichicon
www.nichicon-us.com
www.sanyo.com
Sanyo
Taiyo Yuden
INDUCTORS
Coilcraft
www.t-yuden.com
www.coilcraft.com
www.cooperet.com
www.pulseeng.com
www.sumida.com
www.tokoam.com
Coiltronics
Pulse Engineering
Sumida USA
Toko
______________________________________________________________________________________ 11
24V, 600mA Internal Switch, 100% Duty Cycle,
Step-Down Converter
Table 3. Recommended Components
MAXIMUM
INPUT
VOLTAGE
(V)
I
LX(PEAK)
CURRENT
(A)
LOAD
CURRENT
(mA)
CIRCUIT
INDUCTOR
CAPACITOR
10µH, 1.56A, 70mΩ
Toko D75F 646FY-100M,
10µH, 1.70A, 48mΩ
100µF, 6.3V
Sanyo POSCAP 6TPC100M
1
10 to 24
10 to 24
600
300
1.20
0.60
Sumida CDRH6D28-100NC,
or 10µH, 1.63A, 55mΩ
Toko D75C 646CY-100M 0.055
22µH, 1.17A, 120mΩ
Toko D75F 646FY-220M,
22µH, 1.09A, 115mΩ
Toko D75C 646CY-220M,
or 22µH, 1.20A, 95mΩ
Sumida CDRH6D28-220NC
47µF, 6.3V
Sanyo POSCAP 6TPA47M
2
47µH, 0.54A, 440mΩ
Sumida CDRH5D18-470
22µF, 6.3V, 1210 case
Taiyo Youden JMK325BJ226MM
3
4
5
6
7
8
10 to 24
10 to 24
5 to 15
5 to 15
5 to 15
5 to 15
150
75
0.30
0.15
1.20
0.60
0.30
0.15
100µH, 0.29A, 766mΩ
Sumida CDRH4D28-101
10µF, 6.3V, X7R, 1206 case
Taiyo Youden JMK316BJ106ML
5.4µH, 1.6A, 56mΩ
Sumida CDRH5D18-5R4
100µF, 6.3V
Sanyo POSCAP 6TPC100m
600
300
150
75
10µH, 1.04A, 80mΩ
Toko D73LC 817CY-100M
47µF, 6.3V
Sanyo POSCAP 6TPA47M
22µH, 0.41A, 294mΩ
Sumida CDRH4D18-220
22µF, 6.3V, 1210 case
Taiyo Youden JMK325BJ226MM
47µH, 0.33A, 230mΩ
Coilcraft DS1608C-473
10µF, 6.3V, X7R, 1206 case
Taiyo Youden JMK316BJ106ML
Diode Selection
MAX1776 Stability
The current in the external diode (D1 in Figure 1)
changes abruptly from zero to its peak value each time
the LX switch turns off. To avoid excessive losses, the
diode must have a fast turn-on time and a low forward
voltage.
Instability is frequently caused by excessive noise on
OUT, FB, or GND due to poor layout or improper com-
ponent selection. Instability typically manifests itself as
“motorboating,” which is characterized by grouped
switching pulses with large gaps and excessive low-
frequency output ripple during no-load or light-load
conditions.
Make sure that the diode’s peak current rating exceeds
the peak current limit set by the current limit, and that
its breakdown voltage exceeds V . Use Schottky
IN
PC Board Layout and Grounding
High switching frequencies and large peak currents
make PC board layout an important part of the design.
Poor layout introduces switching noise into the feed-
back path, resulting in jitter, instability, or degraded
performance. High-power traces, highlighted in the
diodes when possible.
12 ______________________________________________________________________________________
24V, 600mA Internal Switch, 100% Duty Cycle,
Step-Down Converter
Typical Application Circuit (Figure 1), should be as
short and wide as possible. Additionally, the current
loops formed by the power components (CIN, COUT,
L1, and D1) should be as short as possible to avoid
radiated noise. Connect the ground pins of these
power components at a common node in a star-ground
configuration. Separate the noisy traces, such as the
LX node, from the feedback network with grounded
copper. Furthermore, keep the extra copper on the
board and integrate it into a pseudo-ground plane.
When using external feedback, place the resistors as
close to the feedback pin as possible to minimize noise
coupling.
Chip Information
TRANSISTOR COUNT: 932
PROCESS: BiCMOS
Package Information
4X S
8
8
MILLIMETERS
INCHES
DIM MIN
MAX
MAX
MIN
-
-
0.043
0.006
0.037
0.014
0.007
0.120
1.10
0.15
0.95
0.36
0.18
3.05
A
0.002
0.030
0.010
0.005
0.116
0.05
0.75
0.25
0.13
2.95
A1
A2
b
E
H
ÿ 0.50 0.1
c
D
e
0.0256 BSC
0.65 BSC
0.6 0.1
E
H
0.116
0.188
0.016
0∞
0.120
2.95
4.78
0.41
0∞
3.05
5.03
0.66
6∞
0.198
0.026
6∞
L
1
1
α
S
0.6 0.1
0.0207 BSC
0.5250 BSC
BOTTOM VIEW
D
TOP VIEW
A1
A2
A
c
α
e
L
b
SIDE VIEW
FRONT VIEW
PROPRIETARY INFORMATION
TITLE:
PACKAGE OUTLINE, 8L uMAX/uSOP
APPROVAL
DOCUMENT CONTROL NO.
REV.
1
21-0036
J
1
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 13
© 2003 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
MAX1776EUA+T CAD模型
引脚图
封装焊盘图
MAX1776EUA+T 替代型号
| 型号 | 制造商 | 描述 | 替代类型 | 文档 |
| MAX1776EUA+ | MAXIM | 暂无描述 | 完全替代 |
|
| MAX1776EUA-T | MAXIM | Switching Regulator, Current-mode, 2A, 200kHz Switching Freq-Max, BICMOS, PDSO8, MSOP-8 | 完全替代 |
|
| MAX1776EUA | MAXIM | 24V, 600mA Internal Switch, 100% Duty Cycle, Step-Down Converter | 类似代替 |
|
MAX1776EUA+T 相关器件
| 型号 | 制造商 | 描述 | 价格 | 文档 |
| MAX1776EUA-T | MAXIM | Switching Regulator, Current-mode, 2A, 200kHz Switching Freq-Max, BICMOS, PDSO8, MSOP-8 | 获取价格 |
|
| MAX1776EVKIT | MAXIM | Evaluation Kit for the MAX1776 | 获取价格 |
|
| MAX1777 | MAXIM | High-Efficiency, Quad Output, Main Power- Supply Controllers for Notebook Computers | 获取价格 |
|
| MAX1777-MAX1999 | MAXIM | High-Efficiency, Quad Output, Main Power- Supply Controllers for Notebook Computers | 获取价格 |
|
| MAX1777EEI | MAXIM | High-Efficiency, Quad Output, Main Power- Supply Controllers for Notebook Computers | 获取价格 |
|
| MAX1777EEI+T | MAXIM | Dual Switching Controller, Current-mode, 300kHz Switching Freq-Max, BICMOS, PDSO28, 0.150 INCH, 0.025 INCH PITCH, QSOP-28 | 获取价格 |
|
| MAX1777EEI-T | MAXIM | Dual Switching Controller, Current-mode, 300kHz Switching Freq-Max, BICMOS, PDSO28, 0.150 INCH, 0.025 INCH PITCH, QSOP-28 | 获取价格 |
|
| MAX1778 | MAXIM | Quad-Output TFT LCD DC-DC Converters with Buffer | 获取价格 |
|
| MAX17783C | ADI | 4.5V至60V、2.5A、高效、降压型DC-DC转换器 | 获取价格 |
|
| MAX1778EUG | MAXIM | Quad-Output TFT LCD DC-DC Converters with Buffer | 获取价格 |
|
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