EXPOSED PAD (PIN 29) IS PGND, MUST BE SOLDERED TO PCB
FE PACKAGE
28-LEAD PLASTIC TSSOP
T
JMAX
= 150°C,
θ
JA
= 30°C/W
EXPOSED PAD (PIN 29) IS PGND, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LTC3126EUFD#PBF
LTC3126IUFD#PBF
LTC3126EFE#PBF
LTC3126IFE#PBF
LTC3126HFE#PBF
LTC3126MPFE#PBF
TAPE AND REEL
LTC3126EUFD#TRPBF
LTC3126IUFD#TRPBF
LTC3126EFE#TRPBF
LTC3126IFE#TRPBF
LTC3126HFE#TRPBF
LTC3126MPFE#TRPBF
http://www.linear.com/product/LTC3126#orderinfo
PART MARKING*
3126
3126
LTC3126FE
LTC3126FE
LTC3126FE
LTC3126FE
PACKAGE DESCRIPTION
28-Lead (4mm × 5mm) Plastic QFN
28-Lead (4mm × 5mm) Plastic QFN
28-Lead Plastic TSSOP (4.4mm)
28-Lead Plastic TSSOP (4.4mm)
28-Lead Plastic TSSOP (4.4mm)
28-Lead Plastic TSSOP (4.4mm)
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
–55°C to 150°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/.
Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
3126f
2
For more information
www.linear.com/LTC3126
LTC3126
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). PV
IN1
= V
IN1
= 24V, PV
IN2
= V
IN2
= 12V,
V
SET1
= V
SET2
= GND, unless otherwise noted.
PARAMETER
Input Operating Voltage
V
IN1
, V
IN2
UVLO Threshold
V
CC
UVLO Threshold
V
IN1
Current in Disable
V
IN2
Current in Disable
V
IN1
Current in Standby
V
IN2
Current in Standby
V
IN1
Current, Operating from V
IN2
V
IN2
Current, Operating from V
IN1
Oscillator Frequency
PWM/SYNC Applied Clock Frequency
PWM/SYNC High Pulse Width
PWM/SYNC Low Pulse Width
Logic Input Threshold (ENA, DIODE, PWM/SYNC)
Feedback Voltage
l
l
elecTrical characTerisTics
CONDITIONS
After Start-Up
V
IN1
/V
IN2
Rising
V
IN1
/V
IN2
Falling
V
CC
Rising
V
CC
Falling
ENA Low, V
IN1
= 24V, V
IN2
= 12V
ENA Low, V
IN1
= 12V, V
IN2
= 24V
ENA Low, V
IN2
= 24V, V
IN1
= 12V
ENA Low, V
IN2
= 12V, V
IN1
= 24V
ENA High, Buck in UVLO, V
IN1
= 24V, V
IN2
= 12V
ENA High, Buck in UVLO, V
IN1
= 12V, V
IN2
= 24V
ENA High, Buck in UVLO, V
IN2
= 24V, V
IN1
= 12V
ENA High, Buck in UVLO, V
IN2
= 12V, V
IN1
= 24V
ENA High, Buck Operating, V
IN1
= 24V, V
IN2
= 27V
ENA High, Buck Operating, V
IN2
= 24V, V
IN1
= 27V
Programmable Frequency
R
T
Resistor = 33.2k
l
l
l
l
l
l
l
MIN
2.4
TYP
2.50
2.34
2.3
2.2
1.35
0.55
1.35
0.55
1.65
0.55
1.65
0.55
1.2
1.2
5.5
MAX
42
2.6
2.4
2.4
2.3
UNITS
V
V
V
V
V
µA
µA
µA
µA
µA
µA
µA
µA
µA
µA
µA
Burst Mode Operation Quiescent Current from V
IN
Not Switching, V
FB
= 0.850V
200
900
200
100
150
0.3
812
804
–20
FB Rising, as a Percentage of the Feedback Voltage
7.4
1000
2200
1100
2200
kHz
kHz
kHz
ns
ns
0.8
818
818
0.2
1
9.8
1.1
7.5
1.1
824
832
20
12
V
mV
mV
%
nA
%
%
ms
Feedback Voltage Line Regulation
Feedback Pin Current
Feedback Pin Overvoltage Comparator Threshold
Feedback Pin Overvoltage Comparator Hysteresis
Soft-Start Duration
PGOOD Threshold
PGOOD Threshold Hysteresis
PGOOD Delay
V
REF
Voltage
V
IN1
, V
IN2
= 2.4V to 42V
FB Falling, as a Percentage of the Feedback Voltage
FB Falling
l
–10.7
–8.7
1
200
–6.6
%
%
µs
l
0.995
0.982
1.000
1.000
13
1.005
1.018
1
V
V
mA
mA
V
V
V
REF
Output Current
V
REF
Current Limit
V
BEST
Comparator Threshold
V
BEST
Comparator Hysteresis
V
BEST
Comparator Delay
V
IN1
, V
IN2
Input Valid Threshold, Rising
V
IN1
Falling, V
IN2
= 24V
V
IN2
Falling, V
IN1
= 24V
V
SET1
= V
SET2
= 1000mV
V
SET1
= V
SET2
= 500mV
V
SET1
= V
SET2
= 250mV
V
SET1
= V
SET2
= 150mV
l
l
l
l
V
IN1
Rising, V
IN2
= 24V
V
IN1
Falling, V
IN2
= 24V
280
24.18
23.83
365
11
40
19.8
9.9
4.9
2.91
20.0
10.0
5.0
3.0
20.2
10.1
5.1
3.09
450
mV
µs
µs
V
V
V
V
3126f
For more information
www.linear.com/LTC3126
3
LTC3126
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). PV
IN1
, = V
IN1
= 24V, PV
IN2
= V
IN2
= 12V,
V
SET1
= V
SET2
= GND, unless otherwise noted.
PARAMETER
V
IN1
, V
IN2
Input Valid Threshold, Falling
CONDITIONS
V
SET1
= V
SET2
= 1000mV
V
SET1
= V
SET2
= 500mV
V
SET1
= V
SET2
= 250mV
V
SET1
= V
SET2
= 150mV
As a Percentage of the Rising Threshold
V
IN1
/V
IN2
Falling, 2V/µs, V
SET1
/V
SET2
= 1V
V
IN1
/V
IN2
Rising, 2V/µs, V
SET1
/V
SET2
= 1V
PGOOD,
PRIORITY, VALID1, VALID2
PGOOD,
PRIORITY, VALID1, VALID2
PGOOD,
PRIORITY, VALID1, VALID2
70
200
1A Load, V
OUT
= 3.3V
(Note 3)
(Note 3)
PWM/SYNC = Low (Note 3)
PWM/SYNC = High or Clocked (Note 3)
V
IN1
= V
IN2
= PV
IN1
= PV
IN2
= 42V, V
SW
= 0V, 42V
I
VCC
= 1mA
V
CC
= 3.5V
Powered from V
IN1
or V
IN2
, V
IN
= 2.4V, I
LOAD
= 5mA
Powered from EXTV
CC
, V
EXTVCC
= 3.3V, I
LOAD
= 5mA
I
LOAD
= 1mA to 15mA
3.15
l
elecTrical characTerisTics
MIN
17.57
8.77
4.34
2.57
TYP
17.75
8.86
4.43
2.65
11
60
120
MAX
17.93
8.95
4.52
2.73
UNITS
V
V
V
V
%
µs
µs
V
IN1
, V
IN2
Input Valid Threshold Hysteresis
V
IN1
, V
IN2
Input Valid Comparator Delay
Open-Drain Output Voltage
Open-Drain Pull-Down Resistance
Open-Drain Leakage
Low Side Switch Resistance
High Side Switch Resistance
Dropout Voltage
High Side Switch Current Limit
Low Side Switch Current Limit
Zero Cross Threshold
SW Leakage Current
V
CC
Voltage
V
CC
Current Limit
V
CC
Drop-Out Voltage
V
CC
Load Regulation
EXTV
CC
Applied Voltage
EXTV
CC
Valid, Rising Threshold
EXTV
CC
Valid, Hysteresis
EXTV
CC
Current in Shutdown
EXTV
CC
Current
Frequency Foldback Threshold on FB
SW Minimum On-Time
SW Minimum Low-Time
SW Frequency Foldback Factor
SW Frequency Divider in Drop-Out
5.5
70
1
V
Ω
µA
mΩ
mΩ
mV
310
3.0
3.8
3.9
5.2
220
0
–3
4.12
35
4.22
67
70
100
1.1
42
3.05
167
0.2
8.8
200
46
100
16
8
3.15
2.95
3
4.32
4.8
6.8
A
A
mA
mA
µA
V
mA
mV
mV
%
V
V
mV
µA
mA
mV
ns
ns
EXTV
CC
= 3.3V, ENA = Low
Switching, f
SW
= 1MHz
V
IN
= 24V, 1A Load, EXTV
CC
= OPEN
V
FB
< 0.2V
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.
Note 2:
The LTC3126 is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC3126E is guaranteed to meet specifications from
0°C to 85°C junction temperature. Specification over the –40°C to
125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LTC3126I specifications are guaranteed over the –40°C to 125°C operating
junction temperature range. The LTC3126H specifications are guaranteed
over the –40°C to 150°C operating junction temperature range. The
LTC3126MP specifications are guaranteed and tested over the –55°C to
150°C operating junction temperature range. High temperatures degrade
operating lifetimes; operating lifetime is derated for junction temperatures
greater than 125°C.
Note 3:
Current measurements are performed when the LTC3126 is
not switching. The current limit values measured in operation will be
somewhat higher due to the propagation delay of the comparators.
Note 4:
This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. The maximum
rated junction temperature will be exceeded when this protection is active.
Continuous operation above the specified absolute maximum operating
junction temperature may impair device reliability or permanently damage
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