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LT3641IUFD#PBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P28
LT3641
1
3641fa
TYPICAL APPLICATION
DESCRIPTION
Dual Monolithic Buck
Regulator with Power-On
Reset and Watchdog Timer
The LT
®
3641 is a dual channel, current mode monolithic buck
switching regulator with a power-on reset and a watchdog
timer. Both regulators are synchronized to a single oscillator
with an adjustable frequency (350kHz to 2.5MHz). At light
loads, both regulators operate in low ripple Burst Mode
®
to maintain high effi ciency and low output ripple.
The high voltage channel is a nonsynchronous buck with
an internal 2.4A top switch that operates from an input
of 4V to 42V and input transient protection to 55V. The
low voltage channel operates from an input of 2.5V to
5.5V. Internal synchronous power switches provide high
effi ciency without the need of external Schottky diode.
Both channels have cycle-by-cycle current limit, providing
protection against shorted outputs.
The power-on reset and watchdog timeout periods are
both adjustable using external capacitors. The window
mode watchdog timer fl ags when the μP pulses group
too close together or too far apart.
The LT3641 is available in a 28-pin 4mm × 5mm QFN
package and 28-pin TSSOP package. Both packages have
an exposed pad for low thermal resistance.
2MHz 5V/0.8A and 3.3V/0.5A Step Down Regulators
FEATURES
APPLICATIONS
n
High Voltage Buck Regulator:
4V to 42V Operating Range
1.3A Output Current
n
Input Transient Protection to 55V
n
Low Voltage Synchronous Buck Regulator:
2.5V to 5.5V Input Voltage Range
1.1A Output Current
n
Synchronizable, Adjustable 350kHz to 2.5MHz
Switching Frequency
n
Programmable Power-On Reset Timer
n
Programmable Window Mode Watchdog Timer
n
Typical Quiescent Current: 290μA
n
Short-Circuit Robust
n
Programmable Soft-Start
n
Low Shutdown Current: I
Q
< 1μA
n
Thermal Shutdown
n
Available in Thermally Enhanced 28-Lead
(4mm × 5mm) QFN and 28-Lead TSSOP Packages
n
Industrial Power Supplies
n
Automotive Electronic Control Units
3641 TA01a
SYNC
PGOOD2
WDE
1nF
1nF
1.5nF
1.5nF
* FOR INPUT VOLTAGES ABOVE 42V RESTRICTIONS APPLY
32.4k
V
OUT2
3.3V/0.5A
V
OUT1
5V/0.8A
22μF
10μF
100k
RST2
EN2
WDO
WDI
FB2
CWDT
CPOR RT GND SS2 SS1
RST1
SW2
SW1EN/UVLO V
IN
V
IN
7V TO 42V*
SW
LT3641
BST
V
IN2
FB1
2.2μH
100k
V
OUT1
μP
226k
49.9k
301k
100k
4.7μH
0.22μF
DA
22μF
HV Channel Effi ciency,
2MHz, V
OUT1
= 5V
L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks
and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
LV Channel Effi ciency,
2MHz, V
OUT2
= 3.3V
V
OUT1
CURRENT (A)
0
70
EFFICIENCY (%)
80
0.2 0.4 0.80.6 1.0
90
75
85
1.2 1.4
3641 TA01b
V
IN
= 12V
V
OUT2
CURRENT (A)
0
70
EFFICIENCY (%)
80
0.2 0.4 0.8 1.00.6 1.2
95
90
75
85
3641 TA01c
V
IN2
= 5V
LT3641
2
3641fa
ABSOLUTE MAXIMUM RATINGS
V
IN
, EN/UVLO Voltage (Note 7) .................................55V
WDE Voltage .............................................................30V
BST Above SW, SW1 Voltage ....................... –0.3V to 6V
SW1 Above SW Voltage ............................... –0.3V to 6V
V
IN2
, SYNC, EN2, PGOOD2, WDI,
WDO, RST1, RST2, Voltages ....................... –0.3V to 6V
SS1, SS2, FB1, FB2, RT, CWDT,
CPOR Voltages………... ........................... –0.3V to 2.5V
(Note 1)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
TOP VIEW
FE PACKAGE
28-LEAD PLASTIC TSSOP
28
27
26
25
24
23
22
21
20
19
18
17
16
15
FB2
PGOOD2
EN/UVLO
SYNC
SS1
FB1
RT
RST2
RST1
WDO
CWDT
CPOR
WDE
WDI
SS2
EN2
GND
SW2
V
IN2
GND
V
IN
BST
SW
SW1
DA
NC
GND
GND
29
GND
θ
JA
= 30°C/W, θ
JC
= 8°C/W
EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB
9 10
TOP VIEW
UFD PACKAGE
28-LEAD (4mm × 5mm) PLASTIC QFN
11 12 13
28 27 26 25 24
14
23
6
5
4
3
2
1
SYNC
SS1
FB1
RT
RST2
RST1
WDO
CWDT
SW2
V
IN2
GND
V
IN
BST
SW
SW1
DA
EN/UVLO
PGOOD2
FB2
SS2
EN2
GND
CPOR
WDE
WDI
GND
GND
NC
7
17
18
19
20
21
22
16
8
15
29
GND
θ
JA
= 43°C/W, θ
JC
= 3.4°C/W
EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB
PIN CONFIGURATION
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3641EFE#PBF LT3641EFE#TRPBF LT3641FE 28-Lead Plastic TSSOP –40°C to 125°C
LT3641IFE#PBF LT3641IFE#TRPBF LT3641FE 28-Lead Plastic TSSOP –40°C to 125°C
LT3641HFE#PBF LT3641HFE#TRPBF LT3641FE 28-Lead Plastic TSSOP –40°C to 150°C
LT3641EUFD#PBF LT3641EUFD#TRPBF 3641
28-Lead (4mm × 5mm) Plastic QFN
–40°C to 125°C
LT3641IUFD#PBF LT3641IUFD#TRPBF 3641
28-Lead (4mm × 5mm) Plastic QFN
–40°C to 125°C
Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based fi nish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifi
cations, go to: http://www.linear.com/tapeandreel/
SW2 Voltage ................................–0.3V to (V
IN2
+ 0.3V)
Operating Junction Temperature Range (Note 2)
LT3641E ................................................. –40°C to 125°C
LT3641I .................................................. –40°C to 125°C
LT3641H ................................................. –40°C to 150°C
Storage Temperature Range ................... –65°C to 150°C
Lead Temperature, FE Only (Soldering, 10 sec) .... 300°C
LT3641
3
3641fa
The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C. V
IN
= 12V, V
IN2
= 3.3V, EN/UVLO = 12V, EN2 = 3.3V, unless otherwise noted.
ELECTRICAL CHARACTERISTICS
PARAMETER CONDITIONS MIN TYP MAX UNITS
V
IN
Undervoltage Lockout Threshold
l
3.6 4 V
V
IN
Undervoltage Release Threshold
l
3.8 4.2 V
Quiescent Current from V
IN
EN/UVLO = 0.3V
Not Switching
0.1
275
1
375
μA
μA
EN/UVLO Threshold Voltage 1.2 1.26 1.3 V
EN/UVLO High Bias Current EN/UVLO = Threshold + 60mV 2 μA
EN/UVLO Low Bias Current EN/UVLO = Threshold – 60mV 0.1 μA
SYNC Input Frequency 0.35 2.5 MHz
SYNC Threshold Voltage 0.4 0.8 1 V
Switching Frequency RT = 32.4k
RT = 182k
l
l
1.75
450
2
500
2.35
550
MHz
kHz
FB1 Voltage
l
1.24 1.265 1.29 V
FB1 Bias Current FB1 = 1.265V 30 100 nA
FB1 Line Regulation 5V < V
IN
< 30V 0.001 %/V
SW1 Minimum Off-Time 70 100 ns
SW1 V
CESAT
I
SW1
= 800mA 400 mV
SW1 Leakage Current 0.1 1 μA
SW1 Current Limit FB1 = 1V (Note 3)
FB1 = 0.1V
l
2.2 2.8
1.8
3.4 A
A
DA Current limit FB1 = 1V (Note 4)
FB1 = 0.1V
l
1.35 1.7
1
2.2 A
A
BST Pin Current I
SW1
= 800mA 30 50 mA
Minimum BST-SW Voltage 2 2.7 V
V
IN2
Minimum Operating Voltage
l
2.3 2.5 V
V
IN2
Maximum Operating Voltage
l
5.5 V
EN2 Threshold Rising
l
1.13 1.18 1.23 V
EN2 Hysteresis 50 80 110 mV
EN2 Bias Current EN2 = EN2 Threshold 50 500 nA
FB2 Voltage
l
585 600 615 mV
FB2 Bias Current FB2 = 0.6V 0 100 nA
FB2 Line Regulation 2.5V < V
IN2
< 5.5V 0.01 %/V
SW2 PMOS Current Limit (Note 5)
l
1.5 1.9 2.2 A
SW2 NMOS Current Limit (Note 5)
l
1.2 1.6 2 A
SW2 PMOS R
DS(ON)
I
SW2
= 0.5A (Note 6) 275 mΩ
SW2 NMOS R
DS(ON)
I
SW2
= 0.5A (Note 6) 200 mΩ
ΔFB2 to Enable PGOOD2 20 40 80 mV
ΔFB2 Hysteresis to Disable PGOOD2 20 40 80 mV
PGOOD2 Voltage FB2 = 0.6V, I
PGOOD2
= 1mA 200 320 mV
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LT3641IUFD#PBF

Mfr. #:
Buy LT3641IUFD#PBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators 42V Dual Monolithic Buck Regulator with Power-On Reset and Watchdog Timer
Lifecycle:
New from this manufacturer.
Delivery:
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