LT8610 [ADI]
High Efficiency 42V/120mA Synchronous Buck;
| 型号： | LT8610 |
| 厂家： | 
ADI |
| 描述： | High Efficiency 42V/120mA Synchronous Buck |
| 文件： | 总20页 (文件大小：2736K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT8604
High Efficiency 42V/120mA
Synchronous Buck
FEATURES
DESCRIPTION
The LT®8604 is a compact, high speed synchronous
monolithic step-down switching regulator that delivers up
to 120mA with high efficiency at constant switching fre-
quency, even up to 2.2MHz. It accepts a wide input voltage
range up to 42V, and consumes only 2.5µA of quiescent
current. Top and bottom power switches are included with
all necessary circuitry to minimize the need for external
components. Low ripple Burst Mode operation enables
high efficiency down to very low output currents while
n
High Efficiency 2MHz Synchronous Operation
n
> 90% Efficiency at 50mA, 12V to 5V
IN
OUT
Ultralow Quiescent Current Burst Mode® Operation
n
n
< 2.5µA I Regulating 24V to 3.3V
Q
IN
OUT
n
Output Ripple < 10mV
P-P
n
n
n
n
n
n
n
n
Wide Input Voltage Range: 3.2V to 42V
Fast Minimum Switch-On Time: 35ns
Adjustable Switching Frequency: 200kHz to 2.2MHz
Allows Tiny Inductors
Accurate 1V Enable Pin Threshold
Internal Compensation
Output Soft-Start and Tracking
Small 10-Lead 3mm × 2mm Side-Wettable
DFN Package
AEC-Q100 Qualified for Automotive Applications
keeping the output ripple below 10mV
.
P-P
Additional features provide for flexible and robust opera-
tion. Internal compensation with peak current mode topol-
ogy allows the use of small inductors and results in fast
transient response and good loop stability. The EN/UV pin
has an accurate 1V threshold and can be used to program
VIN under voltage lockout or to shut down the LT8604
reducing the input supply current to 1µA. A PG flag sig-
n
APPLICATIONS
nals when V
is within 7.5% of the programmed out-
OUT
n
Industrial Sensors
put voltage as well as fault conditions. Thermal shutdown
provides additional protection. The LT8604 is available in
a small 10-Lead 3mm × 2mm DFN package with exposed
pad for low thermal resistance.
n
Industrial Internet of Things
n
4mA to 20mA Current Loops
Flow Meters
Automotive Housekeeping Supplies
n
n
All registered trademarks and trademarks are the property of their respective owners.
TYPICAL APPLICATION
5V, Step-Down Converter
Efficiency at VOUT = 5V
ꢀ00
ꢀ
ꢀꢁ
ꢀ
ꢀ ꢁ00ꢂꢃꢄ
ꢀꢁ
ꢀ
ꢀꢁꢂ
ꢀꢁ
ꢀ.ꢁꢂ ꢃꢄ ꢅꢆꢂ
ꢀ
ꢀ ꢁꢂꢃ
ꢀꢁ
ꢀ0
ꢀꢁ
ꢀ0
ꢀꢁ
ꢀ0
ꢀꢁ
ꢀ0
ꢀꢁ
ꢀꢁꢂ
ꢀꢁꢂꢃ
ꢀ00ꢁꢂ
ꢀꢁꢂꢃ0ꢄ
ꢀ
ꢀꢁꢂ
ꢀꢁꢁ ꢀꢁ
ꢀꢁꢂꢃꢄ
ꢀꢁ
ꢀꢁꢂꢃ
ꢀꢁ
ꢀꢁ
ꢀ
ꢀ ꢁꢂꢃ
ꢀꢁ
ꢀꢁ0ꢂꢃ
ꢀꢁꢂ
ꢀ
ꢀ ꢁꢂꢃ
ꢀꢁ
ꢀꢁꢂꢃ
ꢀꢀ
ꢀRꢁꢂꢂ
ꢀꢁ
Rꢀ
ꢀꢁ
ꢀꢁꢂ
ꢀ0ꢁꢂ
ꢀꢁꢂꢃ
ꢀꢁ0ꢂ ꢃꢄ0ꢅꢆ
ꢀ0.ꢁꢂ
0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ00
ꢀꢁ0
ꢀ
ꢀ ꢁ00ꢂꢃꢄ
ꢀꢁ
ꢀꢁꢂꢃ ꢄꢅRRꢆꢇꢈ ꢉꢊꢂꢋ
ꢀꢁ0ꢂ ꢃꢄ0ꢅꢆ
Rev. 0
1
Document Feedback
For more information www.analog.com
LT8604
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
ꢀꢁꢂ ꢃꢄꢅꢆ
V , EN/UV Voltage .................................... –0.3V to 42V
IN
PG Voltage................................................. –0.3V to 42V
BIAS Voltage.............................................. –0.3V to 25V
FB, TR/SS Voltages...................................... –0.3V to 4V
Operating Junction Temperature Range (Note 2)
LT8604E, LT8604I.................................. –40°C to 125°C
LT8604J................................................. –40°C to 150°C
Storage Temperature Range .................. –65°C to 150°C
ꢇ
ꢔ
ꢒ
ꢥ
ꢠ
ꢇ0
ꢤ
ꢉꢖꢀ
ꢖꢆ
ꢃ
ꢄꢘ
ꢅꢘꢞꢢꢃ
ꢂꢎ
ꢇꢇ
ꢣ
ꢉꢄꢋꢖ
ꢛ
ꢄꢘꢀꢃ
ꢀRꢞꢖꢖ
ꢗꢉ
ꢌꢌ
ꢜ
Rꢀ
ꢈꢈꢉꢊ ꢂꢋꢌꢍꢋꢎꢅ
ꢇ0ꢏꢐꢅꢋꢈ ꢑꢒꢓꢓ × ꢔꢓꢓꢕ ꢂꢐꢋꢖꢀꢄꢌ ꢈꢗꢘ
ꢚ ꢛꢜꢝꢌꢞꢆꢟ θ ꢚ ꢇꢒ.ꢠꢝꢌꢞꢆ
θ
ꢙꢋ
ꢙꢌ
ꢅꢡꢂꢁꢖꢅꢈ ꢂꢋꢈ ꢑꢂꢄꢘ ꢇꢇꢕ ꢄꢖ ꢎꢘꢈꢟ ꢊꢢꢖꢀ ꢉꢅ ꢖꢁꢐꢈꢅRꢅꢈ ꢀꢁ ꢂꢌꢉ
ORDER INFORMATION
Lead Free Finish
TAPE AND REEL (MINI)
TAPE AND REEL
PART MARKING* PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT8604EDDBM#TRMPBF
LT8604EDDBM#TRPBF
LHNB
LHNB
LHNB
10-Lead (3mm × 2mm) Plastic Side-Wettable –40°C to 125°C
DFN Package
LT8604IDDBM#TRMPBF
LT8604JDDBM#TRMPBF
LT8604IDDBM#TRPBF
LT8604JDDBM#TRPBF
10-Lead (3mm × 2mm) Plastic Side-Wettable –40°C to 125°C
DFN Package
10-Lead (3mm × 2mm) Plastic Side-Wettable –40°C to 150°C
DFN Package
AUTOMOTIVE PRODUCTS**
LT8604EDDBM#WTRMPBF
LT8604EDDBM#WTRPBF LHNB
LT8604IDDBM#WTRPBF LHNB
LT8604JDDBM#WTRPBF LHNB
10-Lead (3mm × 2mm) Plastic Side-Wettable –40°C to 125°C
DFN Package
LT8604IDDBM#WTRMPBF
LT8604JDDBM#WTRMPBF
10-Lead (3mm × 2mm) Plastic Side-Wettable –40°C to 125°C
DFN Package
10-Lead (3mm × 2mm) Plastic Side-Wettable –40°C to 150°C
DFN Package
TRM = 500 pieces. *Temperature grades are identified by a label on the shipping container.
Contact the factory for parts specified with wider operating temperature ranges.
Contact the factory for information on lead based finish parts.
Tape and reel specifications. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.
**Versions of this part are available with controlled manufacturing to support the quality and reliability requirements of automotive applications. These
models are designated with a #W suffix. Only the automotive grade products shown are available for use in automotive applications. Contact your
local Analog Devices account representative for specific product ordering information and to obtain the specific Automotive Reliability reports for
these models.
Rev. 0
2
For more information www.analog.com
LT8604
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
l
Minimum Input Voltage
2.9
3.2
V
V
Quiescent Current
V
EN/UV
V
EN/UV
= 0V
1
1.7
4
12
µA
µA
IN
= 2V, Not Switching
V
Current in Regulation
V
IN
V
IN
= 12V, V
= 12V, V
= 3.3V, I
= 3.3V, I
= 100µA
= 1mA
56
400
µA
µA
IN
OUT
OUT
LOAD
LOAD
l
l
l
Feedback Reference Voltage
FB Voltage Line Regulation
FB Pin Input Current
0.762
0.778
0.002
0.798
0.04
20
V
%/V
nA
V
V
V
= 4V to 42V
= 0.8V
IN
FB
BIAS Pin Current Consumption
Minimum On-Time
= 3.3V, I
= 30mA, 700kHz
LOAD
0.9
35
90
mA
ns
BIAS
l
65
Minimum Off-Time
120
ns
l
l
Oscillator Frequency
R = 221k
T
140
1.85
200
2.00
260
2.15
kHz
MHz
T
R = 18.2k
Top Power NMOS On-Resistance
Top Power NMOS Current Limit
Bottom Power NMOS On-Resistance
SW Leakage Current
3.2
230
1.2
Ω
mA
Ω
l
185
275
l
l
V
= 24V
15
µA
IN
EN/UV Pin Threshold
Pin Voltage Rising
0.98
1.04
40
1.11
V
V
EN/UV Pin Hysteresis
EN/UV Pin Current
mV
nA
%
V
V
V
= 2V
20
10.0
EN/UV
l
l
PG Upper Threshold Offset from V
PG Lower Threshold Offset from V
PG Hysteresis
Rising
Falling
5.0
7.5
–7.5
0.5
FB/OUT
FB/OUT
FB/OUT
–5.0
–10.0
%
FB/OUT
%
l
l
PG Leakage
V
V
V
= 42V
200
1200
3.5
nA
Ω
PG
PG Pull-Down Resistance
TR/SS Source Current
= 0.1V
550
2
PG
= 0.1V
1
µA
Ω
TR/SS
TR/SS Pull-Down Resistance
Fault Condition, V
= 0.1V
300
900
TR/SS
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
temperature range. The LT8604J is guaranteed over the full –40°C to
150°C operating junction temperature range. High junction temperatures
degrade operating lifetimes. Operating lifetime is derated at junction
temperatures greater than 125°C.
Note 2: The LT8604E is guaranteed to meet performance specifications
from 0°C to 125°C junction temperature. Specifications over the –40°C
to 125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LT8604I is guaranteed over the full –40°C to 125°C operating junction
Note 3: This IC includes overtemperature protection that is intended to
protect the device during overload conditions. Junction temperature will
exceed 150°C when overtemperature protection is active. Continuous
operation above the specified maximum operating junction temperature
will reduce lifetime
Rev. 0
3
For more information www.analog.com
LT8604
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency (5V Output)
Efficiency (5V Output)
Efficiency (3.3V Output)
ꢀ00
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ00
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
0
ꢀ00
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ
ꢀ ꢁꢂꢃ
ꢀꢁ
ꢀ
ꢀ ꢁꢂꢃ
ꢀꢁ
ꢀ
ꢀ ꢁꢂꢃ
ꢀꢁ
ꢀ
ꢀꢁ
ꢀ ꢁꢂꢃ
ꢀ
ꢀ ꢁꢂꢃ
ꢀꢁ
ꢀ
ꢀ ꢁꢂꢃ
ꢀ
ꢀ ꢁꢂꢃ
ꢀꢁ
ꢀꢁ
ꢀ
ꢀ ꢁꢂꢃ
ꢀꢁ
ꢀ
ꢀ ꢁꢂꢃ
ꢀꢁ
ꢀ ꢁ ꢂꢃꢄꢅ
ꢀ ꢁꢂꢃꢄ
ꢀ ꢁ ꢂꢂꢃꢄ
ꢀ ꢁꢂꢃꢄ
ꢀ ꢁ ꢂꢃꢄꢅ
ꢀ ꢁꢂꢃꢄ
ꢀ
ꢀ
ꢀ
ꢀꢁ
ꢀꢁ
ꢀꢁ
0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ00
ꢀꢁ0
ꢀꢁ
ꢀ0ꢁ
ꢀ00ꢁ
ꢀꢁ
ꢀ0ꢁ
ꢀ00ꢁ
0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ00
ꢀꢁ0
ꢀꢁꢂꢃꢁꢂ ꢄꢁRRꢅꢆꢂ ꢇꢈꢉꢊ
ꢀꢁꢂꢃꢁꢂ ꢄꢁRRꢅꢆꢂ ꢇꢈꢉ
ꢀꢁꢂꢃꢁꢂ ꢄꢁRRꢅꢆꢂ ꢇꢈꢉꢊ
ꢀꢁ0ꢂ ꢃ0ꢄ
ꢀꢁ0ꢂ ꢃ0ꢄ
ꢀꢁ0ꢂ ꢃ0ꢄ
Efficiency (3.3V Output)
Load Regulation
FB Voltage
ꢀ00
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
0
ꢀꢁ0
ꢀꢀꢁ
ꢀꢀꢁ
ꢀꢀꢀ
ꢀꢀꢁ
ꢀꢀꢁ
0.ꢀꢁ
0.ꢀ0
ꢀ ꢁ ꢂꢂꢃꢄ
ꢀRꢁꢂꢃ ꢄꢅꢆꢇ ꢅꢄꢄꢈꢉꢊꢅꢃꢉꢁꢂ
ꢀ
ꢀ ꢁꢂꢃꢄ
ꢀꢁ
0.0ꢀ
ꢀ
ꢀ ꢁꢂꢃ
ꢀꢁ
0.00
ꢀ
ꢀꢁ
ꢀ ꢁꢂꢃ
ꢀ
ꢀ ꢁꢂꢃ
ꢀꢁ
ꢀ0.0ꢁ
ꢀ0.ꢁ0
ꢀ0.ꢁꢂ
ꢀꢁ
ꢀ0ꢁ
ꢀ00ꢁ
ꢀꢁ
ꢀ0ꢁ
ꢀ00ꢁ
ꢀꢁ0 ꢀꢁꢂ
0
ꢀꢁ ꢀ0 ꢀꢁ ꢀ00 ꢀꢁꢂ ꢀꢁ0
0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ00
ꢀꢁ0
ꢀꢁꢂꢃꢁꢂ ꢄꢁRRꢅꢆꢂ ꢇꢈꢉ
ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ
ꢀꢁꢂꢃꢁꢂ ꢄꢁRRꢅꢆꢂ ꢇꢈꢉꢊ
ꢀꢁ0ꢂ ꢃ0ꢂ
ꢀꢁ0ꢂ ꢃ0ꢄ
ꢀꢁ0ꢂ ꢃ0ꢁ
No-Load Supply Current
Line Regulation
ꢀ.0
ꢀ.ꢁ
ꢀ.0
ꢀ.ꢁ
ꢀ.0
ꢀ.ꢁ
ꢀ.0
ꢀ.ꢁ
ꢀ.0
0.ꢀ0
0.ꢀꢁ
0.ꢀ0
0.0ꢀ
0
ꢀ
ꢀꢁꢂ
ꢀ ꢁ.ꢁꢂ
ꢀ ꢁ0ꢂꢃ
ꢀ
ꢀ ꢁ.ꢁꢂ
ꢀꢁꢂ
ꢀꢁꢂ
ꢀ
R1 = 309kΩ
R2 = 1MΩ
ꢀ0.0ꢁ
ꢀ0.0ꢁ
ꢀ0.ꢁꢂ
ꢀ0.ꢁ0
0
ꢀ
ꢀꢁ
ꢀꢁ
ꢀꢁ
ꢀ0
ꢀꢁ
ꢀꢁ
0
ꢀ
ꢀꢁ
ꢀꢁ
ꢀꢁ
ꢀ0
ꢀꢁ
ꢀꢁ
ꢀꢁꢂꢃꢄ ꢅꢆꢇꢄꢈꢉꢊ ꢋꢅꢌ
ꢀꢁꢂꢃꢄ ꢅꢆꢇꢄꢈꢉꢊ ꢋꢅꢌ
ꢀꢁ0ꢂ ꢃ0ꢀ
ꢀꢁ0ꢂ ꢃ0ꢄ
Rev. 0
4
For more information www.analog.com
LT8604
TYPICAL PERFORMANCE CHARACTERISTICS
Top FET Current Limit
vs Duty Cycle
Top FET Current Limit
vs Temperature
Switch Drop vs Temperature
ꢀ00
ꢀ00
ꢀ00
ꢀ00
ꢀ00
ꢀ00
ꢀ00
ꢀ00
0
ꢀꢁ0
ꢀꢀ0
ꢀꢁ0
ꢀ00
ꢀꢁ0
ꢀꢁ0
ꢀꢁ0
ꢀꢁ0
ꢀꢁꢂ
ꢀꢁ0
ꢀꢀꢁ
ꢀꢀ0
ꢀꢁꢂ
ꢀꢁ0
ꢀ0ꢁ
ꢀ00
ꢀꢁꢂꢃꢄꢅ ꢄꢆRRꢇꢈꢃ ꢉ ꢊꢋ0ꢌꢍ
ꢀꢁꢂ ꢃꢄ
ꢀꢁꢂ ꢃꢄ
ꢀꢁ0 ꢀꢁꢂ
0
ꢀꢁ ꢀ0 ꢀꢁ ꢀ00 ꢀꢁꢂ ꢀꢁ0
0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ00
ꢀꢁ0 ꢀꢁꢂ
0
ꢀꢁ ꢀ0 ꢀꢁ ꢀ00 ꢀꢁꢂ ꢀꢁ0
ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ
ꢀꢁꢂꢃ ꢄꢃꢄꢅꢆ ꢇꢈꢉ
ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ
ꢀꢁ0ꢂ ꢃꢄꢄ
ꢀꢁ0ꢂ ꢃ0ꢄ
ꢀꢁ0ꢂ ꢃꢄ0
Minimum Off-Time
vs Temperature
Minimum On-Time
vs Temperature
Switch Drop vs Switch Current
ꢀ00
ꢀ00
ꢀ00
ꢀ00
ꢀ00
0
ꢀꢁ
ꢀꢁ
ꢀꢁ
ꢀꢁ
ꢀ0
ꢀꢁ
ꢀꢁ
ꢀꢁ
ꢀꢀ
ꢀ0
ꢀꢁ
ꢀ00
ꢀꢁ
ꢀ0
ꢀꢁ
ꢀ0
ꢀꢁ
ꢀ0
ꢀ
ꢀ ꢁ00ꢂꢃ
ꢀꢁꢂꢃ
ꢀꢁꢂ ꢃꢄ
ꢀꢁꢂ ꢃꢄ
0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ00
ꢀꢁ0
ꢀꢁ0 ꢀꢁꢂ
0
ꢀꢁ ꢀ0 ꢀꢁ ꢀ00 ꢀꢁꢂ ꢀꢁ0
ꢀꢁ0 ꢀꢁꢂ
0
ꢀꢁ ꢀ0 ꢀꢁ ꢀ00 ꢀꢁꢂ ꢀꢁ0
ꢀꢁꢂꢃꢄꢅ ꢄꢆRRꢇꢈꢃ ꢉꢊꢋꢌ
ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ
ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ
ꢀꢁ0ꢂ ꢃꢄꢅ
ꢀꢁ0ꢂ ꢃꢄꢅ
ꢀꢁ0ꢂ ꢃꢄꢂ
Switching Frequency
vs Temperature
Burst Frequency vs Load Current
Dropout Voltage vs Load Current
ꢀꢁ00
ꢀꢀꢁ0
ꢀ000
ꢀꢁꢂ0
ꢀꢁ00
ꢀꢁꢂ0
ꢀ000
ꢀꢁ0
ꢀ00
ꢀ00
ꢀ00
ꢀ00
ꢀ00
ꢀ00
0
ꢀ0ꢁ0
ꢀ0ꢀ0
ꢀ0ꢁ0
ꢀ000
ꢀꢁꢁ0
ꢀꢁꢂ0
ꢀꢁꢂ0
ꢀꢁꢂ0
ꢀꢁꢂ0
ꢀ ꢁ ꢀꢂꢃꢄ0ꢅ0ꢆꢅꢅꢅꢇR
ꢀ ꢁ ꢂꢂꢃꢄ
R
ꢀ
= 18.2kΩ
ꢀ
ꢀ ꢁ.ꢁꢂ
ꢀ
ꢀ
ꢀ ꢁꢂꢃ
ꢀꢁꢂ
ꢀꢁꢂ
ꢀꢁ
ꢀ ꢁ.ꢁꢂ
ꢀ00
ꢀꢁ0
0
0
ꢀ
ꢀ0
ꢀꢁ
ꢀ0
ꢀꢁ
ꢀ0
0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ00
ꢀꢁ0
ꢀꢁ0 ꢀꢁꢂ
0
ꢀꢁ ꢀ0 ꢀꢁ ꢀ00 ꢀꢁꢂ ꢀꢁ0
ꢀꢁꢂꢃ ꢄꢅRRꢆꢇꢈ ꢉꢊꢂꢋ
ꢀꢁꢂꢃ ꢄꢅRRꢆꢇꢈ ꢉꢊꢂꢋ
ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ
ꢀꢁ0ꢂ ꢃꢄꢅ
ꢀꢁ0ꢂ ꢃꢄꢅ
ꢀꢁ0ꢂ ꢃꢄꢁ
Rev. 0
5
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LT8604
TYPICAL PERFORMANCE CHARACTERISTICS
Soft-Start Tracking
Soft-Start Current vs Temperature
Frequency Foldback
ꢀ.ꢁ
ꢀ.ꢁ
ꢀ.ꢁ
ꢀ.ꢀ
ꢀ.0
ꢀ.ꢁ
ꢀ.ꢁ
ꢀ.ꢁ
ꢀ.ꢁ
ꢀꢁ00
ꢀꢀꢁ0
ꢀ000
ꢀꢁꢂ0
ꢀꢁ00
ꢀꢁꢂ0
ꢀ000
ꢀꢁ0
ꢀ.0
0.ꢀ
0.ꢀ
0.ꢀ
0.ꢀ
0.ꢀ
0.ꢀ
0.ꢀ
0.ꢀ
0.ꢀ
0
Rꢀ ꢀ ꢀꢀ.ꢀꢀΩ
ꢀ00
ꢀꢁ0
0
ꢀꢁ0 ꢀꢁꢂ
0
ꢀꢁ ꢀ0 ꢀꢁ ꢀ00 ꢀꢁꢂ ꢀꢁ0
0
0.ꢀ 0.ꢀ 0.ꢀ 0.ꢀ 0.ꢀ 0.ꢀ 0.ꢀ 0.ꢀ
0
0.ꢀ 0.ꢀ 0.ꢀ 0.ꢀ 0.ꢀ 0.ꢀ 0.ꢀ 0.ꢀ 0.ꢀ ꢀ.0 ꢀ.ꢀ ꢀ.ꢁ
ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ
ꢀꢁ ꢂꢃꢄꢅꢆꢇꢈ ꢉꢂꢊ
ꢀRꢁꢂꢂ ꢃꢄꢅꢀꢆꢇꢈ ꢉꢃꢊ
ꢀꢁ0ꢂ ꢃꢄꢀ
ꢀꢁ0ꢂ ꢃꢄꢅ
ꢀꢁ0ꢂ ꢃꢄ0
VIN UVLO
PG Thresholds
Bias Pin Current
ꢀ0.0
ꢀ.ꢁ
ꢀ.ꢁ
ꢀ.ꢁ
ꢀ.ꢁ
ꢀ.ꢁ
ꢀ.0
0.ꢀ
0.ꢀ
ꢀ.00
ꢀ.ꢁ0
ꢀ.ꢁ0
ꢀ.ꢁ0
ꢀ.ꢀ0
ꢀ.00
ꢀ
ꢀ
ꢀ
ꢀ ꢁꢂꢃ
ꢀꢁ
ꢀ ꢁꢂ
ꢀꢁꢂ
ꢀ ꢁ00ꢂꢃ
Rꢀꢁꢀꢂꢃ
ꢀꢁꢂꢃ
ꢀ.0
ꢀ.ꢁ
0
ꢀꢁ.ꢂ
ꢀꢁ.0
ꢀꢁ.ꢂ
ꢀꢁ0.0
ꢀꢁꢂꢂꢃꢄꢅ
ꢀ
ꢀ
ꢀ ꢁ.ꢁꢂ
ꢀ ꢁꢂ
ꢀꢁꢂꢃ
ꢀꢁꢂꢃ
ꢀꢁ0 ꢀꢁꢂ
0
ꢀꢁ ꢀ0 ꢀꢁ ꢀ00 ꢀꢁꢂ ꢀꢁ0
0.ꢀ 0.ꢀ 0.ꢀ 0.ꢀ
ꢀ
ꢀ.ꢁ ꢀ.ꢁ ꢀ.ꢁ ꢀ.ꢁ ꢀ.0 ꢀ.ꢀ
ꢀꢁ0 ꢀꢁꢂ
0
ꢀꢁ ꢀ0 ꢀꢁ ꢀ00 ꢀꢁꢂ ꢀꢁ0
ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ
ꢀꢁꢂꢃꢄꢅꢂꢆꢇ ꢈRꢉꢊꢋꢉꢆꢄꢌ ꢍꢎꢅꢏꢐ
ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ
ꢀꢁ0ꢂ ꢃꢄꢄ
ꢀꢁ0ꢂ ꢃꢄꢅ
ꢀꢁ0ꢂ ꢃꢄꢅ
Start-Up Dropout
Start-Up Dropout
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
0
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
0
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
R
ꢀꢁꢂꢃ
= 40Ω
R
ꢀꢁꢂꢃ
= 400Ω
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
0
ꢀ
ꢀ
ꢀꢁ
ꢀꢁ
ꢀ
ꢀ
ꢀꢁꢂ
ꢀꢁꢂ
ꢀ
0
0
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
0
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀꢁꢂꢃꢄ ꢅꢆꢇꢄꢈꢉꢊ ꢋꢅꢌ
ꢀꢁꢂꢃꢄ ꢅꢆꢇꢄꢈꢉꢊ ꢋꢅꢌ
ꢀꢁ0ꢂ ꢃꢄꢅ
ꢀꢁ0ꢂ ꢃꢄꢂ
Rev. 0
6
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LT8604
TYPICAL PERFORMANCE CHARACTERISTICS
Switching Waveforms
Switching Waveforms
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ0ꢁꢂꢃꢄꢅꢆ
ꢀ0ꢁꢂꢃꢄꢅꢆ
ꢀ
ꢀ
ꢀꢁ
ꢀꢁ
ꢀꢁꢂꢃꢄꢁ
ꢀ0ꢁꢂꢃꢄꢁ
ꢀRꢁꢂꢃ ꢄꢅꢆꢇ ꢅꢄꢄꢈꢉꢊꢅꢃꢉꢁꢂ
ꢀRꢁꢂꢃ ꢄꢅꢆꢇ ꢅꢄꢄꢈꢉꢊꢅꢃꢉꢁꢂ
ꢀꢁꢂ ꢀꢁ ꢂꢃ
ꢀꢁ ꢂ0ꢃꢀ
ꢀꢁꢂ ꢀꢁ ꢂꢃ ꢀꢁ ꢂ0ꢃꢀ
ꢀꢁ
ꢀꢁꢂ
ꢀꢁ
ꢀꢁꢂ
ꢀꢁ0ꢂ ꢃꢄꢁ
ꢀꢁ0ꢂ ꢃꢄꢅ
ꢀ00ꢁꢂꢃꢄꢅꢆ
ꢀ00ꢁꢂꢃꢄꢅꢆ
Switching Waveforms
Switching Waveforms
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ0ꢁꢂꢃꢄꢅꢆ
ꢀ0ꢁꢂꢃꢄꢅꢆ
ꢀ
ꢀꢁ
ꢀ
ꢀꢁ
ꢀꢁꢂꢃꢄꢁ
ꢀ0ꢁꢂꢃꢄꢁ
ꢀRꢁꢂꢃ ꢄꢅꢆꢇ ꢅꢄꢄꢈꢉꢊꢅꢃꢉꢁꢂ
ꢀRꢁꢂꢃ ꢄꢅꢆꢇ ꢅꢄꢄꢈꢉꢊꢅꢃꢉꢁꢂ
ꢀꢁꢂ ꢀꢁ ꢂꢃ
ꢀꢁ ꢂꢃꢀ
ꢀꢁꢂ ꢀꢁ ꢂꢃ ꢀꢁ ꢂꢃꢀ
ꢀꢁ
ꢀꢁꢂ
ꢀꢁ
ꢀꢁꢂ
ꢀꢁ0ꢂ ꢃꢄꢀ
ꢀꢁ0ꢂ ꢃꢄꢅ
ꢀꢁꢂꢃꢄꢅꢆ
ꢀꢁꢂꢃꢄꢅꢆ
Switching Waveforms
Switching Waveforms
ꢀ
ꢀ ꢁꢂꢃ
ꢀ
ꢀ ꢁꢂꢃ
ꢀꢁ0ꢂꢃ
ꢀꢁ0ꢂꢃ
ꢀꢁ
ꢀꢁ
ꢀ
ꢀꢁꢂꢃ
ꢀ
ꢀꢁꢂꢃ
ꢀ0ꢁꢂꢃꢄꢅꢆ
ꢀ0ꢁꢂꢃꢄꢅꢆ
ꢀ0ꢁꢂ
ꢀ0ꢁꢂ
ꢀ
ꢀ
ꢀꢁꢂ
ꢀꢁꢂ
ꢀ0ꢁꢂꢃꢄꢅꢂ
ꢀ0ꢁꢂꢃꢄꢅꢂ
ꢀRꢁꢂꢃ ꢄꢅꢆꢇ ꢅꢄꢄꢈꢉꢊꢅꢃꢉꢁꢂ
ꢀRꢁꢂꢃ ꢄꢅꢆꢇ ꢅꢄꢄꢈꢉꢊꢅꢃꢉꢁꢂ
ꢀꢁ0ꢂ ꢃꢄ0
ꢀꢁ0ꢂ ꢃꢄꢅ
ꢀ00ꢁꢂꢃꢄꢅꢆ
ꢀ00ꢁꢂꢃꢄꢅꢆ
Rev. 0
7
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LT8604
PIN FUNCTIONS
BST (Pin 1): This pin is used to provide a drive volt-
age higher than the input voltage, to the topside power
switch. Place a 47nF boost capacitor as close as possible
to the IC. Do not put resistance in series with this pin.
LT8604 to regulate the FB pin to equal the TR/SS pin volt-
age. When TR/SS is above 0.778V, the tracking function is
disabled and the internal reference resumes control of the
error amplifier. An internal 2µA pull-up current on this pin
allows a capacitor to program output voltage slew rate.
This pin is pulled to ground with a 300Ω MOSFET during
shutdown and fault conditions; use a series resistor if
driving from a low impedance output.
SW (Pin 2): The SW pin is the output of the internal power
switches. Connect this pin to the inductor. This node
should be kept small on the PCB for good performance.
BIAS (Pin 3): The internal regulator will draw current from
PG (Pin 8): The PG pin is the open-drain output of an
internal comparator. PG remains low until the FB pin is
within 7.5% of the final regulation voltage, and there are
BIAS instead of V when BIAS is tied to a voltage higher
IN
than 3.2V. For output voltages of 3.3V to 25V this pin
should be tied to V . If this pin is tied to a supply other
OUT
no fault conditions. PG is valid when V is above 3.2V,
IN
than V , use a 1µF local bypass capacitor on this pin.
OUT
regardless of EN/UV pin state.
If no supply is available, tie this pin to GND.
EN/UV (Pin 9): The LT8604 is shut down when this pin is
low and active when high. The hysteretic threshold volt-
age is 1.05V rising and 1.00V falling. Tie to VIN if the
shutdown feature is not used. An external resistor divider
INTV (Pin 4): Internal 3.4V Regulator Bypass Pin. The
CC
internal power drivers and control circuits are powered
from this voltage. INTVCC maximum output current is
2mA. Do not load the INTV pin with external circuitry.
INTVCC current will be suCpCplied from BIAS if BIAS >
from V can be used to program a V threshold below
IN
IN
which the LT8604 will shut down.
3.2V, otherwise current will be drawn from V . Voltage
IN
on INTV will vary between 2.8V and 3.4V when V
V (Pin 10): The V pin supplies current to the LT8604
IN IN
CC
is between 3.0V and 3.6V. Decouple this pin to poBwIAeSr
ground with a low ESR ceramic capacitor of at least 1μF
placed close to the IC.
internal circuitry and to the internal top side power switch.
This pin must be locally bypassed. Be sure to place the
positive terminal of the input capacitor as close as pos-
sible to the V pin, and the negative capacitor terminal
IN
RT (Pin 5): Tie a resistor between RT and ground to set
the switching frequency.
as close as possible to the GND pin.
GND (Exposed Pad Pin 11): Ground. The exposed pad
must be connected to the negative terminal of the input
capacitor and soldered to the PCB in order to lower the
thermal resistance.
FB (Pin 6): The LT8604 regulates the FB pin to 0.778V.
Connect the feedback resistor divider tap to this pin.
TR/SS (Pin 7): Output Tracking and Soft-Start Pin. This
pin allows user control of output voltage ramp rate dur-
ing start-up. A TR/SS voltage below 0.778V forces the
Rev. 0
8
For more information www.analog.com
LT8604
BLOCK DIAGRAM
ꢀꢁꢂꢃ
ꢀ
ꢀꢁ
ꢀ
ꢀꢁ
ꢀ0
ꢀ
ꢀ
ꢁꢂ
ꢆ
ꢅ
ꢀꢁꢂꢃRꢁꢄꢅ 0.ꢆꢆꢇꢈ Rꢃꢉ
Rꢀ
ꢀ.ꢁꢂ
Rꢀꢁ
ꢀꢁ
ꢀꢁꢂꢃꢄ
ꢅ
ꢆ
ꢀꢁꢂꢃ
ꢀꢁꢂꢃ
ꢀꢀ
ꢀ
ꢀꢁꢂꢃꢄ ꢅꢂꢆꢃ
ꢀ
Rꢀ
ꢀ
ꢀꢁꢂꢃꢄꢄ
R
ꢀ
ꢀꢁꢂ
Rꢀ
ꢀꢁꢂꢃꢄꢄꢅꢆꢀR
ꢀ
ꢀ00ꢁꢂꢃ ꢄꢅ ꢀ.ꢀꢆꢂꢃ
ꢀ
ꢀRRꢁR
ꢀ.ꢁꢂ
ꢀꢁ
ꢀꢁꢂ
ꢀ
ꢀ
ꢀꢁꢂ
ꢀꢁ
ꢀꢁꢂꢃꢄꢅ
ꢀꢁꢂꢃꢄ
ꢀ
ꢅ
ꢅ
ꢆ
ꢀ
ꢀꢁRꢂꢃ
ꢀꢁꢂꢁꢃꢂ
ꢀꢁ
ꢀ
ꢀ
ꢀꢁꢂ
ꢀ
ꢀꢁꢂ
ꢀꢁꢂꢃꢄ
ꢀꢁꢂꢂꢃ
ꢀꢁRꢂꢃꢄꢁ
ꢀ
ꢀꢁꢂ
ꢀꢁꢂꢃ
ꢀꢁ
ꢀꢁꢂ
ꢀꢁꢂ
ꢀꢁꢂꢃ ꢀꢁꢂꢃ
ꢀꢀ
ꢀ
ꢀꢁꢂꢃ
ꢀꢁ
ꢀ
ꢀꢀ
ꢀꢁꢂ
ꢀRꢁꢂꢂ
ꢀ
ꢀꢀ
ꢀꢁꢂꢃ
ꢀꢁꢂ
ꢀꢁꢂꢃ
ꢀ
ꢀꢁ
ꢀꢁ
ꢀ
Rꢀ
Rꢀ
ꢀꢁ0ꢂ ꢃꢄ
Rev. 0
9
For more information www.analog.com
LT8604
OPERATION
associated with controlling the output switch is shut down
reducing the input supply current to 1.7µA. In a typical
application with a 24V input, 2.5µA will be consumed from
the input supply when regulating with no load.
The LT8604 is a monolithic constant-frequency current
mode step-down DC/DC converter. Operation is best
understood by referring to the Block Diagram. An internal
oscillator turns on the integrated top power switch at the
beginning of each clock cycle. Current in the inductor then
increases until the top switch current comparator trips
and turns off the top power switch. The peak inductor cur-
rent at which the top switch turns off is controlled by the
voltage on the internal VC node. The error amplifier servos
To improve efficiency across all loads, supply current to
internal circuitry can be sourced from the BIAS pin when
biased at 3.2V or above. Else, the internal circuitry will
draw current from V . The BIAS pin should be connected
IN
to V
if the LT8604 output is programmed to a voltage
between 3.3V and 25V.
OUT
the V node by comparing the voltage on the FB pin with
C
an internal reference. When the load current increases, it
Comparators monitoring the FB pin voltage will pull the PG
causes a reduction in the feedback voltage relative to the
pin low if the output voltage varies more than 7.5% (typi
-
reference leading the error amplifier to raise the V volt-
C
cal) from the set point, or if a fault condition is present.
age until the average inductor current matches the new
load current. When the top power switch turns off, the
synchronous power switch turns on until the next clock
cycle begins or inductor current falls to zero. If overload
conditions result in excess current flowing through the
bottom switch, the next clock cycle will be delayed until
switch current returns to a safe level.
In the LT8604, the oscillator reduces its operating fre-
quency when the voltage at the FB pin is low. This fre-
quency foldback helps to control the inductor current
when the output voltage is lower than the programmed
value which occurs during start-up.
If the EN/UV pin is low, the LT8604 is shut down and
draws 1µA from the input. When the EN/UV pin is above
1.05V, the switching regulator becomes active.
To optimize efficiency, the LT8604 enters Burst Mode
operation at light loads. Between bursts, all circuitry
Rev. 0
10
For more information www.analog.com
LT8604
APPLICATIONS INFORMATION
Achieving Ultralow Quiescent Current
ꢀ
ꢀꢁꢂ
ꢀꢁꢂꢃꢄꢅꢂ
To enhance efficiency at light loads, the LT8604 enters
into low ripple Burst Mode operation, which keeps the
output capacitor charged to the desired output voltage
while minimizing the input quiescent current and minimiz-
ing output voltage ripple. In Burst Mode operation, the
LT8604 delivers single small pulses of current to the out-
put capacitor followed by sleep periods where the output
power is supplied by the output capacitor. While in sleep
mode the LT8604 consumes 1.7μA.
ꢀ
ꢀ
ꢀ0ꢁꢂꢃꢄꢅꢆ
ꢀ
ꢀꢁ
ꢀꢁꢂꢃꢄꢁ
ꢀꢁ0ꢂ ꢃ0ꢄ
ꢀꢁꢂꢃꢄꢅꢆ
Figure 2. Burst Mode Operation
As the output load decreases, the frequency of single cur-
rent pulses decreases (see Figure 1) and the percentage
of time the LT8604 is in sleep mode increases, result-
ing in much higher light load efficiency than for typical
converters. By maximizing the time between pulses, the
converter quiescent current approaches 2.5µA for a typi-
cal application when there is no output load. Therefore,
to optimize the quiescent current performance at light
loads, the current in the feedback resistor divider must
be minimized as it appears to the output as load current.
to the switching frequency programmed by the resistor
at the RT pin as shown in Figure 1. The output load at
which the LT8604 reaches the programmed frequency
varies based on input voltage, output voltage, and induc-
tor choice.
FB Resistor Network
The output voltage is programmed with a resistor divider
between the output and the FB pin. Choose the resistor
values according to:
ꢀꢁ00
ꢀ ꢁ ꢂꢂꢃꢄ
VOUT
0.778V
⎛
⎝
⎞
⎠
ꢀꢀꢁ0
ꢀ000
ꢀꢁꢂ0
ꢀꢁ00
ꢀꢁꢂ0
ꢀ000
ꢀꢁ0
ꢀ
ꢀ ꢁꢂꢃ
ꢀꢁ
R2 = R1
– 1
⎟
⎜
ꢀ
ꢀ ꢁ.ꢁꢂ
ꢀꢁꢂ
1% resistors are recommended to maintain output volt-
age accuracy.
The total resistance of the FB resistor divider should be
selected to be as large as possible when good low load
efficiency is desired: The resistor divider generates a
small load on the output, which should be minimized to
optimize the quiescent current at low loads.
ꢀ00
ꢀꢁ0
0
0
ꢀ
ꢀ0
ꢀꢁ
ꢀ0
ꢀꢁ
ꢀ0
ꢀꢁꢂꢃ ꢄꢅRRꢆꢇꢈ ꢉꢊꢂꢋ
ꢀꢁ0ꢂ ꢃ0ꢄ
Setting the Switching Frequency
Figure 1. SW Burst Mode Frequency vs Load
The LT8604 uses a constant frequency PWM architec-
ture that can be programmed to switch from 200kHz to
2.2MHz by using a resistor tied from the RT pin to ground.
Table 1 shows the necessary RT value for a desired
switching frequency.
While in Burst Mode operation, the current limit of the top
switch is approximately 40mA resulting in output voltage
ripple shown in Figure 2. As the load ramps upward from
zero the switching frequency will increase but only up
Rev. 0
11
For more information www.analog.com
LT8604
APPLICATIONS INFORMATION
Table 1. SW Frequency vs RT Value
The LT8604 is capable of maximum duty cycle approach-
ing 100%, and the V to V dropout is limited by the
DS(ON)
f
(MHz)
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.2
1.4
1.6
1.8
2.0
2.2
R (kΩ)
IN
OUT
SW
T
R
of the top switch. In this mode the LT8604 skips
221
143
switch cycles, resulting in a lower switching frequency
than programmed by R .
110
T
86.6
71.5
60.4
52.3
46.4
40.2
33.2
27.4
23.7
20.5
18.2
16.2
For applications that cannot allow deviation from the pro-
grammed switching frequency at low VIN/VOUT ratios, use
the following formula to set switching frequency:
V
+ V
SW(BOT)
OUT
V
=
– V
+ V
IN(MIN)
SW(BOT) SW(TOP)
1– f • t
SW OFF(MIN)
where VIN(MIN) is the minimum input voltage without
skipped cycles, V is the output voltage, V and
OUT
SW(TOP)
V
are the internal switch drops (~0.38V, ~0.14V,
SW(BOT)
respectively at max load), f is the switching frequency
(set by RT), and tOFF(MIN)SiWs the minimum switch off-
time. Note that higher switching frequency will increase
the minimum input voltage below which cycles will be
dropped to achieve higher duty cycle.
Operating Frequency Selection and Trade-Offs
Selection of the operating frequency is a trade-off
between efficiency, component size, and input voltage
range. The advantage of high frequency operation is that
smaller inductor and capacitor values may be used. The
disadvantages are lower efficiency and a smaller input
voltage range.
Inductor Selection and Maximum Output Current
The LT8604 is designed to minimize solution size by
allowing the inductor to be chosen based on the output
load requirements of the application. During overload or
short circuit conditions the LT8604 safely tolerates opera-
tion with a saturated inductor through the use of a high
speed peak-current mode architecture.
The highest switching frequency (f
) for a given
SW(MAX)
application can be calculated as follows:
V
+ V
OUT
SW(BOT)
f
=
SW(MAX)
A good first choice for the inductor value is:
t
V – V
+ V
(
)
IN
ON(MIN)
SW(TOP) SW(BOT)
V
OUT + VSW(BOT)
L =
• 20
where V is the typical input voltage, V
is the output
OUT
voltage,INV
and V
are the internal switch
fSW
drops (~0S.3W8(VTO, P~)0.14V,SrWes(BpOeTc)tively at max load) and
tON(MIN) is the minimum top switch on-time (see Electrical
Characteristics). This equation shows that slower switch-
where fSW is the switching frequency in MHz, VOUT is
the output voltage, V
is the bottom switch drop
SW(BOT)
(~0.14V) and L is the inductor value in μH.
ing frequency is necessary to accommodate a high V /
IN
To avoid overheating and poor efficiency, an inductor
must be chosen with an RMS current rating that is greater
than the maximum expected output load of the applica-
tion. In addition, the saturation current (typically labeled
V
OUT
ratio.
For transient operation V may go as high as the Abs Max
rating regardless of theINRT value, however the LT8604
will reduce switching frequency as necessary to maintain
control of inductor current to assure safe operation.
Rev. 0
12
For more information www.analog.com
LT8604
APPLICATIONS INFORMATION
I
) rating of the inductor must be higher than the load
Finally, for duty cycles greater than 50%, a minimum
inductance is required to avoid sub-harmonic oscillation:
SAT
current plus 1/2 of the inductor ripple current:
1
2
VOUT + VSW(BOT)
I
L(PEAK) =ILOAD(MAX) + ΔL
LMIN
=
•12.5
fSW
where ∆IL is the inductor ripple current as calculated sev-
eral paragraphs below and ILOAD(MAX) is the maximum
output load for a given application.
where f is the switching frequency, V
is the output
OUT
SW
voltage, V
is the bottom switch drop (~0.14V) and
SW(BOT)
is the inductor value.
L
MIN
As a quick example, an application requiring 120mA out-
put should use an inductor with an RMS rating of greater
Input Capacitor
than 120mA and an I of greater than 180mA. To keep
SAT
Bypass the input of the LT8604 circuit with a ceramic
capacitor of X7R or X5R type. Y5V types have poor perfor-
mance over temperature and applied voltage, and should
not be used. A 1μF to 2.2μF ceramic capacitor is adequate
to bypass the LT8604 and will easily handle the ripple
current. If the input power source has high impedance, or
there is significant inductance due to long wires or cables,
additional bulk capacitance may be necessary. This can
be provided with a low performance electrolytic capacitor.
the efficiency high, the series resistance (DCR) should be
less than 1Ω, and the core material should be intended
for high frequency applications.
The LT8604 limits the peak switch current in order to
protect the switches and the system from overload faults.
The top switch current limit (I ) is at least 185mA at
LIM
low duty cycles and decreases linearly to 137mA at D =
0.8. The inductor value must then be sufficient to supply
the desired maximum output current (I
), which
is a function of the switch current limOitUT(I(LMIMAX)) and the
ripple current:
Step-down regulators draw current from the input sup-
ply in pulses with very fast rise and fall times. The input
capacitor is required to reduce the resulting voltage rip-
ple at the LT8604 and to force this very high frequency
switching current into a tight local loop, minimizing EMI.
A 1μF capacitor is capable of this task, but only if it is
placed close to the LT8604 (see the PCB Layout section).
A second precaution regarding the ceramic input capaci-
tor concerns the maximum input voltage rating of the
LT8604. A ceramic input capacitor combined with trace
or cable inductance forms a high quality (under damped)
tank circuit. If the LT8604 circuit is plugged into a live
supply, the input voltage can ring to twice its nominal
value, possibly exceeding the LT8604’s voltage rating.
This situation is easily avoided (see Analog Devices
Application Note 88).
ΔIL
2
IOUT(MAX) =ILIM
–
The peak-to-peak ripple current in the inductor can be
calculated as follows:
⎛
⎞
VOUT
L•fSW
VOUT
V
IN(MAX)
ΔIL =
1–
⎜
⎟
⎝
⎠
where f is the switching frequency of the LT8604, and
SW
L is the value of the inductor. Therefore, the maximum
output current that the LT8604 will deliver depends on
the switch current limit, the inductor value, and the input
and output voltages. The inductor value may have to be
increased if the inductor ripple current does not allow
Output Capacitor and Output Ripple
sufficient maximum output current (I
) given the
OUT(MAX)
The output capacitor has two essential functions. Along
with the inductor, it filters the square wave generated
by the LT8604 to produce the DC output. In this role it
determines the output ripple, thus low impedance at the
switching frequency is important. The second function is
switching frequency, and maximum input voltage used in
the desired application.
For more information about maximum output current and
discontinuous operation, see Analog Devices Application
Note 44.
Rev. 0
13
For more information www.analog.com
LT8604
APPLICATIONS INFORMATION
to store energy in order to satisfy transient loads and sta- twice its nominal value, possibly exceeding the LT8604’s
bilize the LT8604’s control loop. Ceramic capacitors have rating. This situation is easily avoided (see Analog Devices
very low equivalent series resistance (ESR) and provide Application Note 88).
the best ripple performance. A good starting value is:
EN/UV Pin
50
COUT
=
The LT8604 is in shutdown when the EN/UV pin is low
and active when the pin is high. The rising threshold of
the EN/UV comparator is 1.05V, with 50mV of hysteresis.
The EN/UV pin can be tied to V if the shutdown feature
is not used, or tied to a logic IlNevel if shutdown control
is required.
VOUT SW
f
where fSW is the switching frequency in MHz, VOUT is
the output voltage, and C is the recommended output
OUT
capacitance in μF. Use X5R or X7R types. This choice will
provide low output ripple and good transient response.
Transient performance can be improved with a higher value
output capacitor and the addition of a feedforward capaci-
Adding a resistor divider from VIN to EN/UV programs
the LT8604 to regulate the output only when V is above
a desired voltage (see Block Diagram). TypIiNcally, this
threshold, VIN(EN/UV), is used in situations where the input
supply is current limited, or has a relatively high source
resistance. A switching regulator draws constant power
from the source, so source current increases as source
voltage drops. This looks like a negative resistance load
to the source and can cause the source to current limit
or latch low under low source voltage conditions. The
tor placed between V
and FB. Increasing the output
OUT
capacitance will also decrease the output voltage ripple. A
lower value of output capacitor can be used to save space
and cost but transient performance will suffer and may
cause loop instability. See the Typical Applications in this
data sheet for suggested capacitor values.
When choosing a capacitor, special attention should be
given to the data sheet to calculate the effective capaci-
tance under the relevant operating conditions of voltage
bias and temperature. A physically larger capacitor or one
with a higher voltage rating may be required.
V
threshold prevents the regulator from operating
IN(EN/UV)
at source voltages where the problems might occur. This
threshold can be adjusted by setting the values R3 and
R4 such that they satisfy the following equation:
Ceramic Capacitors
V
⎛
⎝
⎞
⎠
R3= IN(EN/UV) –1 •R4
⎜
⎟
Ceramic capacitors are small, robust and have very low
ESR. However, ceramic capacitors can cause problems
1V
when used with the LT8604 due to their piezoelectric where the LT8604 will remain off until V is above V
.
IN
nature. When in Burst Mode operation, the LT8604’s Due to the comparator’s hysteresis, switching willINn(oEtNs/UtoVp)
switching frequency depends on the load current, and at until the input falls slightly below V
very light loads the LT8604 can excite the ceramic capacitor
.
IN(EN/UV)
For light-load currents, the current through the VIN(EN/UV)
resistor network can easily be greater than the supply current
at audio frequencies, generating audible noise. Since the
LT8604 operates at a lower current limit during Burst Mode
operation, the noise is typically very quiet. If this is unac-
ceptable, use a high performance tantalum or electrolytic
capacitor at the output.
consumed by the LT8604. Therefore, the V
tors should be large to minimize their effect on efficiency at
resis-
IN(EN/UV)
low loads.
INTV Regulator
A final precaution regarding ceramic capacitors concerns
the maximum input voltage rating of the LT8604. As
previously mentioned, a ceramic input capacitor com-
bined with trace or cable inductance forms a high qual-
ity (under damped) tank circuit. If the LT8604 circuit is
plugged into a live supply, the input voltage can ring to
CC
An internal low dropout (LDO) regulator produces the
3.4V supply from VIN that powers the drivers and the
internal bias circuitry. The INTVCC can supply enough cur-
rent for the LT8604’s circuitry and must be bypassed to
Rev. 0
14
For more information www.analog.com
LT8604
APPLICATIONS INFORMATION
will pull the PG pin low. To prevent glitching both the
upper and lower thresholds include 0.5% of hysteresis.
ground with a minimum of 1μF ceramic capacitor. Good
bypassing is necessary to supply the high transient cur-
rents required by the power MOSFET gate drivers. To
improve efficiency, the internal LDO can also draw cur-
rent from the BIAS pin when the BIAS pin is at 3.2V or
higher. Typically, the BIAS pin can be tied to the output of
the LT8604 or can be tied to an external supply of 3.3V or
The PG pin is also actively pulled low during several fault
conditions: EN/UV pin is below 1V, INTV has fallen too
CC
low, V is too low, or thermal shutdown.
IN
Shorted and Reversed Input Protection
above. If BIAS is connected to a supply other than V
,
be sure to bypass with a local ceramic capacitor. IfOtUhTe
BIAS pin is below 3.0V, the internal LDO will consume
The LT8604 will tolerate a shorted output. Several features
are used for protection during output short-circuit and
brownout conditions. The first is the switching frequency
will be folded back while the output is lower than the set
point to maintain inductor current control. Second, the
bottom switch current is monitored such that if inductor
current is beyond safe levels switching of the top switch
will be delayed until such time as the inductor current
falls to safe levels. This allows for tailoring the LT8604
to individual applications and limiting thermal dissipation
during short circuit conditions.
current from V . Applications with high input voltage and
IN
high switching frequency where the internal LDO pulls
current from VIN will increase die temperature because
of the higher power dissipation across the LDO. Do not
connect an external load to the INTV pin.
CC
Output Voltage Tracking and Soft-Start
The LT8604 allows the user to program its output voltage
ramp rate by means of the TR/SS pin. An internal 2μA
pulls up the TR/SS pin to INTVCC. Putting an external
capacitor on TR/SS enables soft-starting the output to
prevent current surge on the input supply. During the
soft-start ramp the output voltage will proportionally track
the TR/SS pin voltage. For output tracking applications,
TR/SS can be externally driven by another voltage source.
From 0V to 0.778V, the TR/SS voltage will override the
internal 0.778V reference input to the error amplifier, thus
regulating the FB pin voltage to that of TR/SS pin. When
TR/SS is above 0.778V, tracking is disabled and the feed-
back voltage will regulate to the internal reference voltage.
There is another situation to consider in systems where
the output will be held high when the input to the LT8604
is absent. This may occur in battery charging applications
or in battery backup systems where a battery or some
other supply is diode ORed with the LT8604’s output. If
the V pin is allowed to float and the EN/UV pin is held
IN
high (either by a logic signal or because it is tied to V ),
IN
then the LT8604’s internal circuitry will pull its quiescent
current through its SW pin. This is acceptable if the sys-
tem can tolerate several μA in this state. If the EN/UV pin
is grounded the SW pin current will drop to near 0.7µA.
However, if the VIN pin is grounded while the output is held
high, regardless of EN/UV, parasitic body diodes inside
the LT8604 can pull current from the output through the
An active pull-down circuit is connected to the TR/SS pin
which will discharge the external soft-start capacitor in
the case of fault conditions and restart the ramp when the
faults are cleared. Fault conditions that clear the soft-start
SW pin and the V pin. Figure 3 shows a connection of
IN
the V and EN/UV pins that will allow the LT8604 to run
IN
capacitor are the EN/UV pin transitioning low, V voltage
IN
only when the input voltage is present and that protects
falling too low, or thermal shutdown.
against a shorted or reversed input.
Output Power Good
ꢉꢊ
ꢀ
ꢁꢂ
ꢀ
ꢁꢂ
When the LT8604’s output voltage is within the 7.5%
window of the regulation point, which is a V voltage in
the range of 0.720V to 0.836V (typical), the output voltage
is considered good and the open-drain PG pin goes high
impedance and is typically pulled high with an external
resistor. Otherwise, the internal drain pull-down device
ꢃꢄꢅꢆ0ꢇ
ꢍꢂꢎꢏꢀ
ꢈꢂꢉ
FB
ꢅꢆ0ꢇ ꢋ0ꢌ
Figure 3. Reverse VIN Protection
Rev. 0
15
For more information www.analog.com
LT8604
APPLICATIONS INFORMATION
PCB Layout
on the same side of the circuit board, and their connec-
tions should be made on that layer. Place a local, unbroken
ground plane under the application circuit on the layer
closest to the surface layer. The SW and BOOST nodes
should be as small as possible. Finally, keep the FB and
RT nodes small so that the ground traces will shield them
from the SW and BOOST nodes. The exposed pad on the
bottom of the package must be soldered to ground so that
the pad is connected to ground electrically and also acts
as a heat sink thermally. To keep thermal resistance low,
extend the ground plane as much as possible, and add
thermal vias near the LT8604 to additional ground planes
within the circuit board and on the bottom side.
For proper operation and minimum EMI, care must be
taken during printed circuit board layout. Figure 4 shows
the recommended component placement with trace,
ground plane and via locations. Note that large, switched
currents flow in the LT8604’s VIN pins, GND pins, and the
input capacitor (CIN). The loop formed by the input capaci-
tor should be as small as possible by placing the capacitor
adjacent to the V and GND pins. When using a physically
IN
large input capacitor the resulting loop may become too
large in which case using a small case/value capacitor
placed close to the V and GND pins plus a larger capaci-
IN
tor further away is preferred. These components, along
Figure 4 shows the basic guidelines for a layout example.
with the inductor and output capacitor, should be placed
ꢀ
ꢀꢁꢂ
ꢀ
ꢀꢁꢂ
ꢀ
ꢀꢁꢂ
ꢀꢁ
ꢀ
ꢀ
ꢀꢁ
ꢀꢁꢂ
ꢀ
LT8604
ꢀꢁꢂ
ꢀꢁ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ0
ꢀ
ꢀꢁꢂꢃꢄ
ꢀꢁ
ꢀꢀ
ꢀꢁꢂꢃ
ꢀ
ꢀꢁꢂꢃ
ꢀRꢁꢂꢂ
ꢀꢁ
ꢀ
ꢀꢀ
ꢀ
Rꢀ
ꢀ
ꢀꢁꢂꢃꢄꢄ
ꢀꢁꢂ
ꢀꢁꢂ
Rꢀ
R
ꢀ
Rꢀ
ꢀ
ꢀꢁ
ꢀ
ꢀꢁꢂ
ꢀꢁꢂꢃ
ꢀꢁ0ꢂ ꢃ0ꢂ
Figure 4. Recommended PCB Layout (Not to Scale)
Rev. 0
16
For more information www.analog.com
LT8604
TYPICAL APPLICATIONS
5V Step-Down Converter
Typical Performance Minimum
Load to Full Frequency
ꢀ
ꢀꢁ
ꢀ
ꢀꢁꢂ
ꢀꢁ
ꢀꢁ
ꢀꢁ
ꢀ0
ꢀꢁ
ꢀꢁ
ꢀꢁ
ꢀ
ꢀ.ꢁꢂ ꢃꢄ ꢅꢆꢂ
ꢀ
ꢀꢁꢂꢃ
ꢀꢁꢂ
ꢁ00ꢂꢃ
ꢀ
ꢀꢁꢂ
ꢀꢁꢂꢃꢄ
ꢀꢁ
ꢀꢁ
ꢀꢁꢂꢃ0ꢄ
ꢀꢁ0ꢂꢃ
ꢀ00ꢁ
ꢀꢁꢂꢃR
ꢀꢁꢁꢂ
ꢀꢁ
ꢀꢁꢂꢃ
ꢀꢁꢂꢃ
ꢀꢀ
ꢀꢁꢂ
ꢀRꢁꢂꢂ
ꢀꢁꢂꢂ ꢀRꢃꢄꢁꢃꢅꢆꢇ
ꢀꢁ
ꢀ0ꢁꢂ
Rꢀ
ꢀꢁ
ꢀꢁꢂ
ꢀ0ꢁꢂ
ꢀꢃꢄ
ꢀꢁR
ꢀꢁ0ꢂ
0
0
ꢀꢁꢂꢃ
ꢀꢁ ꢀꢂꢃꢄ0ꢅ0ꢆꢇ0ꢈꢉR
ꢀ0.ꢁꢂ
0
0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ00
ꢀꢁ0
ꢀ
ꢀ ꢁ00ꢂꢃꢄ
ꢀꢁ
ꢀꢁꢂꢃ ꢄꢅRRꢆꢇꢈ ꢉꢊꢂꢋ
ꢀꢁ0ꢂ ꢃꢄ0ꢅꢆ
3.3V 2MHz Step-Down Converter
Typical Performance Minimum
Load to Full Frequency
ꢀ
ꢀꢁ
ꢀ
ꢀꢁꢂ
ꢀꢁ
ꢀꢁ
ꢀꢁ
ꢀ0
ꢀꢁ
ꢀꢁ
ꢀꢁ
ꢀ
ꢀ.ꢁꢂ ꢃꢄ ꢀꢁꢂ
ꢀ
ꢀꢁꢂꢃ
ꢀꢁꢂ
ꢁꢁꢂꢃ
ꢀ
ꢀꢁꢂ
ꢀꢁꢂꢃꢄ
ꢀꢁ
ꢀ.ꢀꢁ
ꢀꢁꢂꢃ0ꢄ
ꢀꢁ0ꢂꢃ
ꢀ00ꢁ
ꢀꢁꢂꢃR
ꢀꢁꢁꢂ
ꢀꢁ
ꢀꢁꢂꢃ
ꢀꢁꢂꢃ
ꢀꢀ
ꢀꢁꢂ
ꢀRꢁꢂꢂ
ꢀꢁꢂꢂ ꢀRꢃꢄꢁꢃꢅꢆꢇ
ꢀꢁ
ꢀ0ꢁꢂ
Rꢀ
ꢀꢁ
ꢀꢁꢂ
ꢀ0ꢁꢂ
ꢀꢃꢄ
ꢀꢁR
ꢀꢁ0ꢂ
0
0
ꢀ0ꢁꢂ
ꢀꢁ ꢀꢂꢃꢄ0ꢅ0ꢆꢅꢅꢅꢇR
ꢀꢁ.ꢂꢃ
ꢀ ꢁꢂꢃꢄ
0
ꢀ
0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ00
ꢀꢁ0
ꢀꢁ
ꢀꢁꢂꢃ ꢄꢅRRꢆꢇꢈ ꢉꢊꢂꢋ
ꢀꢁ0ꢂ ꢃꢄ0ꢂꢅ
5V 2MHz Step-Down Converter
Typical Performance Minimum
Load to Full Frequency
ꢀꢁꢂꢃ
ꢀꢁ
ꢀꢁ
ꢀ0
ꢀꢁ
ꢀꢁ
ꢀꢁ
ꢀ
ꢀ
ꢀꢁ
ꢀ
ꢀꢁꢂ
ꢀ
ꢀꢁ
ꢀ.ꢁꢂ ꢃꢄ ꢅꢆꢂ
ꢁꢂꢃꢄ
ꢀꢁꢂ
ꢀ
ꢀꢁꢂ
ꢀꢁꢂꢃꢄ
ꢀꢁ
ꢀꢁ
ꢀꢁ0ꢂꢃ
ꢀ00ꢁ
ꢀꢁꢂꢃ0ꢄ
ꢀꢁꢂꢃR
ꢀꢁꢁꢂ
ꢀꢁꢂꢃ
ꢀꢁ
ꢀꢀ
ꢀꢁꢂ
ꢀRꢁꢂꢂ
ꢀꢁꢂꢃ
ꢀ0ꢁꢂ
ꢀꢁꢂꢂ ꢀRꢃꢄꢁꢃꢅꢆꢇ
ꢀꢁ
Rꢀ
ꢀꢁ
ꢀ0ꢁꢂ
ꢀꢁꢂ
ꢀꢁ.ꢂꢃ
ꢀꢃꢄ
ꢀꢁR
ꢀꢁ0ꢂ
ꢀꢁꢂꢃ
ꢀꢁ ꢀꢂꢃꢄ0ꢅ0ꢆꢇꢈꢅꢉR
0
0
0
0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ00
ꢀꢁ0
ꢀ
ꢀ ꢁꢂꢃꢄ
ꢀꢁ
ꢀꢁꢂꢃ ꢄꢅRRꢆꢇꢈ ꢉꢊꢂꢋ
ꢀꢁ0ꢂ ꢃꢄ0ꢅꢆ
Rev. 0
17
For more information www.analog.com
LT8604
TYPICAL APPLICATIONS
Typical Performance Minimum
Load to Full Frequency
1.8V Step-Down Converter
ꢀꢁꢂꢃ
ꢀꢁ
ꢀꢁ
ꢀ0
ꢀꢁ
ꢀꢁ
ꢀꢁ
ꢀ
ꢀ
ꢀꢁ
ꢀ
ꢀꢁꢂ
ꢀꢁ
ꢀ
ꢀ.ꢁꢂ ꢃꢄ ꢅꢁꢂ
ꢁꢂꢃꢄ
ꢀꢁꢂ
ꢀ
ꢀꢁꢂ
ꢀꢁꢂꢃꢄ
ꢀꢁ
ꢀ.ꢁꢂ
ꢀꢁ0ꢂꢃ
ꢀꢁꢂꢃ0ꢄ
ꢀ00ꢁ
ꢀꢁꢂꢃR
ꢀꢁꢁꢂ
ꢀꢁꢂꢃ
ꢀꢁ
ꢀꢀ
ꢀꢁꢂꢀRꢃꢄꢅ ꢆꢇꢈRꢉꢀ
ꢊꢋ.ꢌꢍ ꢇR ꢎꢃꢏ
ꢀꢁꢂ
ꢀRꢁꢂꢂ
ꢀꢁꢂꢃ
ꢀꢁꢂ
ꢀꢁꢂꢂ ꢀRꢃꢄꢁꢃꢅꢆꢇ
ꢀ0ꢁꢂ
ꢀꢁ
Rꢀ
ꢀꢁ
ꢀꢁꢂꢃ
ꢀꢁꢂ
ꢀꢀ0ꢁ
ꢀꢁꢂꢃ
ꢄ0ꢅ
ꢀꢁR
ꢀꢁꢀ0
0
0
0
0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ00
ꢀꢁ0
ꢀ
ꢀ ꢁ00ꢂꢃꢄ
ꢀꢁ ꢀꢂꢃꢄ0ꢅ0ꢆꢇꢈꢅꢉR
ꢀꢁ
ꢀꢁꢂꢃ ꢄꢅRRꢆꢇꢈ ꢉꢊꢂꢋ
ꢀꢁ0ꢂ ꢃꢄ0ꢁꢅ
12V Step-Down Converter
Typical Performance Minimum
Load to Full Frequency
ꢀꢁꢂꢃ
ꢀꢁ
ꢀꢁ
ꢀ0
ꢀꢁ
ꢀꢁ
ꢀꢁ
ꢀ
ꢀ
ꢀꢁ
ꢀ
ꢀꢁꢂ
ꢀꢁ
ꢀ
ꢀꢁ.ꢂꢃ ꢄꢅ ꢆꢁꢃ
ꢀꢁꢂ
ꢁꢁ0ꢂꢃ
ꢀ
ꢀꢁꢂ
ꢀꢁꢂꢃꢄ
ꢀꢁ
ꢀꢁꢂ
ꢀꢁ0ꢂꢃ
ꢀꢁꢂꢃ0ꢄ
ꢀ00ꢁ
ꢀꢁꢂꢃR
ꢀꢁꢁꢂ
ꢀꢁꢂꢃ
ꢀꢁ
ꢀꢀ
ꢀꢁꢂ
ꢀꢁꢂꢂ ꢀRꢃꢄꢁꢃꢅꢆꢇ
ꢀRꢁꢂꢂ
ꢀꢁꢂꢃ
ꢀ0ꢁꢂ
ꢀꢁ
Rꢀ
ꢀꢁ
ꢀ.ꢀꢁꢂ
ꢃ0ꢄ
ꢀꢁꢂ
ꢀ0.ꢁꢂ
ꢀꢁ.ꢂꢃ
0
0
ꢀꢁR
0
ꢀꢁ0ꢂ
0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ00
ꢀꢁ0
ꢀ
ꢀ ꢁꢂꢃꢄ
ꢀꢁ ꢀꢂꢃꢄ0ꢅ0ꢆꢇꢇꢈꢉR
ꢀꢁ
ꢀꢁꢂꢃ ꢄꢅRRꢆꢇꢈ ꢉꢊꢂꢋ
ꢀꢁ0ꢂ ꢃꢄ0ꢅꢆ
Rev. 0
18
For more information www.analog.com
LT8604
PACKAGE DESCRIPTION
DDBM Package
10-Lead Plastic SIDE WETTABLE DFN (3mm × 2mm)
ꢂReꢩeꢪeꢫꢬe ꢘꢊꢏ ꢅꢍꢎ ꢭ 0ꢠꢓ0ꢨꢓꢁꢣꢠꢠ Rev ꢌꢇ
R ꢦ 0.ꢁꢁꢠ
0.ꢠ0 ±0.ꢁ0
ꢚ.00 ±0.ꢁ0
ꢂꢀ ꢃꢄꢅꢆꢃꢇ
ꢊꢢꢕ
ꢣ
ꢁ0
ꢀ.00 ±0.ꢁ0
ꢕꢄꢈ ꢁ ꢝꢌR
ꢊꢉꢕ ꢑꢌRꢖ
ꢕꢄꢈ ꢁ
ꢂꢀ ꢃꢄꢅꢆꢃꢇ
R ꢦ 0.ꢀ0 ꢉR
ꢂꢃꢆꢆ ꢈꢉꢊꢆ ꢣꢇ
0.ꢀꢠ × ꢛꢠ°
0.ꢀꢠ ±0.ꢁ0
ꢏꢞꢌꢑꢐꢆR
ꢂꢀ ꢃꢄꢅꢆꢃꢇ
ꢠ
ꢁ
ꢂꢅꢅꢝꢑꢁ0ꢇ ꢅꢐꢈ ꢁꢀꢁꢨ Rꢆꢒ ꢌ
0.ꢀꢠ ±0.0ꢠ
0.ꢥꢠ ±0.0ꢠ
0.ꢀ00 Rꢆꢐ
0.ꢠ0 ꢝꢃꢏ
ꢅꢆꢊꢌꢄꢘ ꢌ
ꢀ.ꢠ0 ±0.ꢁ0
ꢂꢀ ꢃꢄꢅꢆꢃꢇ
0 ꢧ 0.0ꢠ
ꢝꢉꢊꢊꢉꢑ ꢒꢄꢆꢍꢤꢆꢜꢕꢉꢃꢆꢅ ꢕꢌꢅ
ꢅꢆꢊꢌꢄꢘ ꢌ
ꢈꢉꢊꢆꢋ
ꢁ. ꢅRꢌꢍꢄꢈꢎ ꢏꢉꢈꢐꢉRꢑꢃ ꢊꢉ ꢒꢆRꢃꢄꢉꢈ ꢂꢍꢆꢏꢅꢓꢁꢇ ꢄꢈ ꢔꢆꢅꢆꢏ ꢕꢌꢏꢖꢌꢎꢆ ꢉꢗꢊꢘꢄꢈꢆ ꢑ0ꢓꢀꢀꢙ
ꢀ. ꢅRꢌꢍꢄꢈꢎ ꢈꢉꢊ ꢊꢉ ꢃꢏꢌꢘꢆ
ꢚ. ꢌꢘꢘ ꢅꢄꢑꢆꢈꢃꢄꢉꢈꢃ ꢌRꢆ ꢄꢈ ꢑꢄꢘꢘꢄꢑꢆꢊꢆRꢃ
ꢊꢆRꢑꢄꢈꢌꢘ ꢘꢆꢈꢎꢊꢞ
0.ꢠ0 0.ꢁ0
0.ꢀ0ꢚ Rꢆꢐ
ꢊꢆRꢑꢄꢈꢌꢘ ꢊꢞꢄꢏꢖꢈꢆꢃꢃ
ꢛ. ꢅꢄꢑꢆꢈꢃꢄꢉꢈꢃ ꢉꢐ ꢆꢜꢕꢉꢃꢆꢅ ꢕꢌꢅ ꢉꢈ ꢝꢉꢊꢊꢉꢑ ꢉꢐ ꢕꢌꢏꢖꢌꢎꢆ ꢅꢉ ꢈꢉꢊ ꢄꢈꢏꢘꢗꢅꢆ
ꢑꢉꢘꢅ ꢐꢘꢌꢃꢞ. ꢑꢉꢘꢅ ꢐꢘꢌꢃꢞꢟ ꢄꢐ ꢕRꢆꢃꢆꢈꢊꢟ ꢃꢞꢌꢘꢘ ꢈꢉꢊ ꢆꢜꢏꢆꢆꢅ 0.ꢁꢠꢡꢡ ꢉꢈ ꢌꢈꢢ ꢃꢄꢅꢆ
ꢠ. ꢆꢜꢕꢉꢃꢆꢅ ꢕꢌꢅ ꢃꢞꢌꢘꢘ ꢝꢆ ꢃꢉꢘꢅꢆR ꢕꢘꢌꢊꢆꢅ
0.ꢁ0 Rꢆꢐ
0.0ꢠ Rꢆꢐ
ꢕꢘꢌꢊꢆꢅ ꢌRꢆꢌ
ꢣ. ꢃꢞꢌꢅꢆꢅ ꢌRꢆꢌ ꢄꢃ ꢉꢈꢘꢢ ꢌ RꢆꢐꢆRꢆꢈꢏꢆ ꢐꢉR ꢕꢄꢈ ꢁ ꢘꢉꢏꢌꢊꢄꢉꢈ ꢉꢈ ꢊꢞꢆ ꢊꢉꢕ ꢌꢈꢅ ꢝꢉꢊꢊꢉꢑ ꢉꢐ ꢕꢌꢏꢖꢌꢎꢆ
0.ꢀꢠ ±0.0ꢠ
ꢂꢀ ꢃꢄꢅꢆꢃꢇ
0.ꢥ0 ±0.0ꢠ
ꢀ.ꢠꢠ ±0.0ꢠ
ꢁ.ꢁꢠ ±0.0ꢠ
ꢕꢌꢏꢖꢌꢎꢆ
ꢉꢗꢊꢘꢄꢈꢆ
0.ꢀꢠ ±0.0ꢠ
0.ꢠ0 ꢝꢃꢏ
ꢀ.ꢠ0 ±0.0ꢠ
ꢂꢀ ꢃꢄꢅꢆꢃꢇ
Rꢆꢏꢉꢑꢑꢆꢈꢅꢆꢅ ꢃꢉꢘꢅꢆR ꢕꢌꢅ ꢕꢄꢊꢏꢞ ꢌꢈꢅ ꢅꢄꢑꢆꢈꢃꢄꢉꢈꢃ
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog
Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications
19
subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
LT8604
TYPICAL APPLICATION
Typical Performance Minimum
Load to Full Frequency
2.5V Step-Down Converter
ꢀꢁꢂꢃ
ꢀꢁ
ꢀꢁ
ꢀ0
ꢀꢁ
ꢀꢁ
ꢀꢁ
ꢀ
ꢀ
ꢀꢁ
ꢀ
ꢀꢁꢂ
ꢀꢁ
ꢀ
ꢀ.ꢁꢂ ꢃꢄ ꢁꢅꢂ
ꢁꢂꢃꢄ
ꢀ
ꢀꢁꢂ
ꢀꢁꢂ
ꢀꢁꢂꢃꢄ
ꢀꢁ
ꢀ.ꢁꢂ
ꢀꢁ0ꢂꢃ
ꢀꢁꢂꢃ0ꢄ
ꢀ00ꢁ
ꢀꢁꢂꢃR
ꢀꢁꢁꢂ
ꢀꢁꢂꢃ
ꢀꢁ
ꢀꢀ
ꢀꢁꢂꢀRꢃꢄꢅ ꢆꢇꢈRꢉꢀ
ꢊꢋ.ꢌꢍ ꢇR ꢎꢃꢏ
ꢀꢁꢂ
ꢀRꢁꢂꢂ
ꢀꢁꢂꢃ
ꢀꢁꢂ
ꢀ0ꢁꢂ
ꢀꢁꢂꢂ ꢀRꢃꢄꢁꢃꢅꢆꢇ
ꢀꢁ
Rꢀ
ꢀꢁ
ꢀꢀꢁꢂ
ꢀꢁꢂ
ꢀ0.ꢁꢂ
ꢀꢁꢂꢃ
ꢃꢄꢅ
ꢀꢁR
ꢀꢁꢀ0
ꢀꢁ0ꢂ ꢃꢄ0ꢅ
0
0
ꢀ0
ꢀ0
ꢀ0
ꢀ0
ꢀ00
ꢀꢁ0
ꢀ
ꢀ ꢁ00ꢂꢃꢄ
ꢀꢁ ꢀꢂꢃꢄ0ꢅ0ꢆꢇꢈꢅꢉR
ꢀꢁ
ꢀꢁꢂꢃ ꢄꢅRRꢆꢇꢈ ꢉꢊꢂꢋ
ꢀꢁ0ꢂ ꢃꢄ0ꢅꢆ
RELATED PARTS
PART NUMBER DESCRIPTION
COMMENTS
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Q
42V, 2.5A, 96% Efficiency, 2.2MHz Synchronous MicroPower Step-Down
V
IN
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Q SD
OUT(MIN)
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Q
42V, 2.5A, 96% Efficiency, 2.2MHz Synchronous MicroPower Step-Down
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42V, Dual 2.5A + 1.5A, 95% Efficiency, 2.2MHz Synchronous
V
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OUT(MIN) Q SD
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MicroPower Step-Down DC/DC Converter with I = 5µA
TSSOP-28E, 3mm × 6mm QFN-28 Packages
Q
65V, 2.5A, 96% Efficiency, 2.2MHz Synchronous MicroPower Step-Down
V
IN
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Q
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DC/DC Converter with I = 2.5µA
MSOP-16E, 3mm × 5mm QFN-24 Packages
Q
42V, 4A, 96% Efficiency, 2.2MHz Synchronous MicroPower Step-Down
V
IN
= 3.4V to 42V, V = 0.97V, I = 2.5µA, I < 1µA,
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Q
SD
DC/DC Converter with I = 2.5µA
3mm × 4mm QFN-18 Package
Q
42V, 6A, 96% Efficiency, 2.2MHz Synchronous MicroPower Step-Down
V
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3mm × 6mm QFN-28 Package
Q
42V, 5A/7A Peak, 96% Efficiency, 3MHz Synchronous MicroPower Step-
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Q
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3mm × 4mm QFN-18 Package
Q
42V, Quad Output (2.5A+1.5A+1.5A+1.5A) 95% Efficiency, 2.2MHz
V
IN
= 3V to 42V, V = 0.8V, I = 25µA, I < 1µA,
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Q
SD
Synchronous MicroPower Step-Down DC/DC Converter with I = 25µA
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Rev. 0
12/20
www.analog.com
ANALOG DEVICES, INC. 2020
20
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