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LTC3785IUF#TRPBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20
LTC3785
1
3785fc
Typical applicaTion
DescripTion
10V, High Efficiency,
Synchronous, No R
SENSE
Buck-Boost Controller
The LTC
®
3785 is a high power synchronous buck-boost
controller that drives all N-channel power MOSFETs from
input voltages above, below and equal to the output volt-
age. With an input range of 2.7V to 10V, the LTC3785 is
well suited for a wide variety of single or dual cell Li-Ion
or multicell alkaline/NiMH applications.
The operating frequency can be programmed from
100kHz to 1MHz. The soft-start time and current limit are
also programmable. The soft-start capacitor doubles as
the fault timer which can program the IC to latch off or
recycle after a determined off time. Burst Mode opera-
tion is user controlled and can be enabled by driving the
MODE pin high.
Protection features include foldback current limit, short-
circuit and overvoltage protection.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. No R
SENSE
is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Efficiency vs Input Voltage
FeaTures
applicaTions
n
Single Inductor Architecture Allows V
IN
Above,
Below or Equal to V
OUT
n
2.7V to 10V Input and Output Range
n
Up to 96% Efficiency
n
Up to 10A of Output Current
n
All N-channel MOSFETs, No R
SENSE
™
n
True Output Disconnect During Shutdown
n
Programmable Current Limit and Soft-Start
n
Optional Short-Circuit Shutdown Timer
n
Output Overvoltage and Undervoltage Protection
n
Programmable Frequency: 100kHz to 1MHz
n
Selectable Burst Mode
®
Operation
n
Available in 24-Lead (4mm × 4mm) Exposed Pad
QFN Package
n
Palmtop Computers
n
Handheld Instruments
n
Wireless Modems
n
Cellular Telephones
V
CC
I
SVIN
TG1
V
SENSE
BG1
FB
V
C
TG2
BG2
SW2
3785 TA01a
V
BST1
SW1
I
SSW1
I
SVOUT
RT
V
DRV
I
SSW2
V
BST2
CCM
I
LSET
MODE
RUN/SS
V
IN
V
OUT
LTC3785
GND
4.7µF
V
IN
2.7V
TO 10V
V
OUT
3.3V
5A
22µF
4.7µH
100µF
0.22µF
0.22µF
270pF
1.3k
205k 121k
12k
42.2k
59k
121k
205k
1nF
1nF
V
IN
(V)
2.5
EFFICIENCY (%)
95
10
3785 TA01b
90
85
4
5.5
7 8.5
100
I
LOAD
= 1A
V
OUT
= 3.3V
F
OSC
= 500kHz
I
LOAD
= 2A
LTC3785
2
3785fc
The l denotes the specifications which apply over the full operating junction
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= I
SVOUT
= V
DRV
= V
BST1
= V
BST2
= 3.6V, R
T
= 49.9k, R
ILSET
= 59k.
pin conFiguraTionabsoluTe MaxiMuM raTings
Input Supply Voltage (V
IN
) ......................... –0.3V to 11V
I
SVOUT
, I
SVIN
.............................................. –0.3V to 11V
SW1, SW2, I
SSW1
, I
SSW2
Voltage:
DC ............................................................. –1V to 11V
Pulsed, <1µs
............................................. –2V to 12V
RUN/SS, MODE, CCM, V
DRV
, V
CC
Voltages .. –0.3V to 6V
V
BST1
Voltage ............................................. –0.3V to 16V
With Respect to SW1 ............................... –0.3V to 6V
V
BST2
Voltage ............................................. –0.3V to 16V
With Respect to SW2 ............................... –0.3V to 6V
Peak Driver Output Current < 10µs
(TG1, TG2, BG1, BG2) .................................................3A
V
CC
Average Output Current .................................100mA
Operating Junction Temperature Range
(Note 2) ..................................................–40°C to 125°C
Junction Temperature ........................................... 125°C
Storage Temperature Range ...................–65°C to 150°C
(Note 1)
24 23 22 21 20 19
7 8 9
TOP VIEW
25
GND
UF PACKAGE
24-LEAD (4mm s 4mm) PLASTIC QFN
10 11 12
6
5
4
3
2
1
13
14
15
16
17
18RUN/SS
V
C
FB
V
SENSE
I
LSET
CCM
I
SSW1
BG1
V
DRV
BG2
I
SSW2
SW2
V
IN
V
CC
I
SVIN
V
BST1
TG1
SW1
RT
MODE
NC
I
SVOUT
V
BST2
TG2
T
JMAX
= 125°C, θ
JA
= 40°C/W 1 LAYER BOARD, θ
JA
= 30°C/W 4 LAYER BOARD
EXPOSED PAD (PIN 25) IS GND, MUST BE SOLDERED TO PCB
PARAMETER CONDITIONS MIN TYP MAX UNITS
V
IN
Supply
Input Operating Voltage
l
2.7 10 V
Quiescent Current—Burst Mode Operation V
C
= 0V, MODE = 3.6V (Note 4) 86 200 µA
Quiescent Current—Shutdown RUN/SS = 0V, I
SVOUT
= 3.6V 15 25 µA
Quiescent Current—Active MODE = 0V (Note 4) 0.8 1.5 mA
Error Amp
Feedback Voltage (Note 5)
l
1.200 1.225 1.25 V
Feedback Input Current 1 500 nA
orDer inForMaTion
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3785EUF#PBF LTC3785EUF#TRPBF 3785
24-Lead (4mm × 4mm) Plastic QFN
–40°C to 85°C
LTC3785IUF#PBF LTC3785IUF#TRPBF 3785
24-Lead (4mm × 4mm) Plastic QFN
–40°C to 125°C
LEAD BASED FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3785EUF LTC3785EUF#TR 3785
24-Lead (4mm × 4mm) Plastic QFN
–40°C to 85°C
LTC3785IUF LTC3785IUF#TR 3785
24-Lead (4mm × 4mm) Plastic QFN
–40°C to 125°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/
This product is only offered in trays. For more information go to: http://www.linear.com/packaging/
elecTrical characTerisTics
LTC3785
3
3785fc
The l denotes the specifications which apply over the full operating junction
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= I
SVOUT
= V
DRV
= V
BST1
= V
BST2
= 3.6V, R
T
= 49.9k, R
ILSET
= 59k.
elecTrical characTerisTics
PARAMETER CONDITIONS MIN TYP MAX UNITS
Error Amp Source Current –500 µA
Error Amp Sink Current 900 µA
Error Amp A
VOL
90 dB
Overvoltage Threshold V
SENSE
Pin % Above FB
LTC3785E
LTC3785I
l
l
6
6
10
10
14
15
%
%
Undervoltage Threshold V
SENSE
Pin % Below FB
LTC3785E
LTC3785I
l
l
–3.5
–3.5
–6.5
–6.5
–9.5
–10.5
%
%
V
SENSE
Input Current V
SENSE
= Measured FB Voltage 1 500 nA
V
CC
Regulator
V
CC
Maximum Regulating Voltage V
IN
= 5V, I
VCC
= –20mA
l
4.15 4.35 4.55 V
V
CC
Regulation Voltage V
IN
= 3.6V, I
VCC
= –20mA
l
3.3 3.5 3.6 V
V
CC
Regulator Sink Current I
SVOUT
= V
CC
= 5V 800 µA
Run/Soft-Start
RUN/SS Threshold When IC is Enabled
When EA is at Maximum Boost Duty Cycle
l
0.35 0.7
1.9
1.1 V
V
RUN/SS Input Current RUN/SS = 0V –1 µA
RUN/SS Discharge Current During Current Limit 20 30 µA
Current Limit
Current Limit Sense Threshold I
SVIN
to I
SSW1
, R
ILSET
= 121k
I
SVIN
to I
SSW1
, R
ILSET
= 59k
l
l
20
55
60
105
100
155
mV
mV
Reverse Current Limit Sense Threshold I
SSW2
to I
SVOUT
, CCM > 2V
I
SSW2
to I
SVOUT
, CCM < 0.4V, LTC3785E
I
SSW2
to I
SVOUT
, CCM < 0.4V, LTC3785I
l
l
–50 –110
–15
–15
–170
–35
–40
mV
mV
mV
Input Current I
SVIN
I
SVOUT
I
SSW1
, I
SSW2
80
10
0.1
150
20
5
µA
µA
µA
CCM Input Threshold (High)
l
2.2 V
CCM Input Threshold (Low)
l
0.4 V
CCM Input Current CCM = 3.6V 0.01 1 µA
Burst Mode Operation
Mode Threshold
l
0.8 1.5 2.2 V
Mode Input Current 0.01 1 µA
t
ON
Time 1.4 µs
Oscillator
Frequency Accuracy
l
370 509 650 kHz
Switching Characteristics
Maximum Duty Cycle Boost (% Switch BG2 On)
Buck (% Switch TG1 On)
l
80 90
99
%
%
TG1, TG2 Driver Impedance 2 Ω
BG1, BG2 Driver Impedance 2 Ω
TG1, TG2 Rise Time C
LOAD
= 3300pF (Note 3) 20 ns
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20

LTC3785IUF#TRPBF

Mfr. #:
Buy LTC3785IUF#TRPBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators High Efficiency, Synchronous, No Rsense, 4-Switch Buck-Boost Controller
Lifecycle:
New from this manufacturer.
Delivery:
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