FeaTures
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LTC3417A
Dual Synchronous
1.5A/1A 4MHz Step-Down
DC/DC Regulator
DescripTion
The LTC
®
3417A is a dual constant frequency, synchronous
step-down DC/DC converter. Intended for medium power
applications, it operates from a 2.25V to 5.5V input volt-
age range and has a constant programmable switching
frequency, allowing the use of tiny, low cost capacitors
and inductors 2mm or less in height. Each output voltage
is adjustable from 0.8V to 5V. Internal, synchronous, low
R
DS(ON)
power switches provide high efficiency without
the need for external Schottky diodes.
A user selectable mode input allows the user to trade
off ripple voltage for light load efficiency. Burst Mode
®
operation provides high efficiency at light loads, while
Pulse Skip mode provides low ripple noise at light loads.
A phase mode pin allows the second channel to operate
in-phase or 180° out-of-phase with respect to channel 1.
Out-of-phase operation produces lower RMS current on V
IN
and thus a lower RMS derating on the input capacitor.
To further maximize battery life, the P-channel MOSFETs
are turned on continuously in dropout (100% duty cycle)
and both channels draw a total quiescent current of only
125µA. In shutdown, the device draws <1µA.
L,
LT, LTC, LTM and Burst Mode are registered trademarks and Hot Swap and ThinSOT are
trademarks of Linear Technology Corporation. All other trademarks are the property of their
respective owners. Protected by U.S. Patents including 5481178, 6580258, 6304066, 6127815,
6498466, 6611131, 6144194.
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High Efficiency: Up to 95%
1.5A/1A Guaranteed Minimum Output Current
Synchronizable to External Clock
No Schottky Diodes Required
Programmable Frequency Operation: 1.5MHz or
Adjustable From 0.6MHz to 4MHz
Low R
DS(ON)
Internal Switches
Short-Circuit Protected
V
IN
: 2.25V to 5.5V
Current Mode Operation for Excellent Line and Load
Transient Response
125µA Quiescent Current in Sleep Mode
Ultralow Shutdown Current: I
Q
< 1µA
Low Dropout Operation: 100% Duty Cycle
Power Good Output
Phase Pin Selects 2nd Channel Phase Relationship
with Respect to 1st Channel
Internal Soft-Start with Individual Run Pin Control
Available in Small Thermally Enhanced
(5mm × 3mm) DFN and 20-Lead TSSOP Packages
GPS/Navigation
Digital Cameras
PC Cards
Wireless and DSL Modems
General Purpose Point of Load DC/DC
applicaTions
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Typical applicaTion
V
IN
2.5V TO 5.5V
10µF
1.5µH
22pF
511k
47µF
412k
I
TH1
5.9k
2200pF
GND
I
TH2
2.87k
6800pF
3417 TA01
OUT2 Efficiency
(Burst Mode Operation)
100
REFER TO FIGURE 4
EFFICIENCY
10
1
POWER LOSS (W)
0.1
0.01
80
75
70
0.001
POWER LOSS
V
IN
= 3.6V
V
OUT
= 2.5V
FREQ = 1MHz
0.01
0.1
LOAD CURRENT (A)
1
3417 TA01a
V
IN
FREQ
SW1
V
IN
RUN1
LTC3417A
V
FB1
V
FB2
SW2
RUN2
2.2µH
V
IN
22pF
866k
412k
22µF
V
OUT2
2.5V
1A
95
EFFICIENCY (%)
90
85
V
OUT1
1.8V
1.5A
0.001
0.0001
3417afc
1
LTC3417A
absoluTe MaxiMuM raTings
(Note 1)
V
IN1
, V
IN2
Voltages ...................................... – 0.3V to 6V
SYNC/MODE, SW1, SW2, RUN1,
RUN2, V
FB1
, V
FB2
, PHASE, FREQ,
I
TH1
, I
TH2
Voltages............... – 0.3V to (V
IN1
/V
IN2
+ 0.3V)
V
IN1
– V
IN2
, V
IN2
– V
IN1
.......................................... 0.3V
PGOOD Voltage ........................................... – 0.3V to 6V
Operating Ambient Temperature Range
(Note 2) ..................................................– 40°C to 85°C
Junction Temperature (Notes 7, 8) ...................... 125°C
Storage Temperature Range...................– 65°C to 125°C
pin conFiguraTion
TOP VIEW
TOP VIEW
RUN1
V
IN1
ITH1
V
FB1
V
FB2
I
TH2
RUN2
V
IN2
1
2
3
4
5
6
7
8
17
16 PGND1
15 SW1
14 PHASE
13 GNDA
12 FREQ
11 PGOOD
10 SW2
9
SYNC/MODE
GNDD
RUN1
V
IN1
I
TH1
V
FB1
V
FB2
I
TH2
RUN2
V
IN2
1
2
3
4
5
6
7
8
9
21
20 GNDD
19 PGND1
18 SW1
17 PHASE
16 GNDA
15 FREQ
14 PGOOD
13 SW2
12 SYNC/MODE
11 PGND2
DHC PACKAGE
16-LEAD (3mm
×
5mm) PLASTIC DFN
PGND2 10
T
JMAX
= 125°C,
θ
JA
= 43°C/W
EXPOSED PAD (PIN 17) IS PGND2/GNDD, MUST BE SOLDERED TO PCB
FE PACKAGE
20-LEAD PLASTIC TSSOP
T
JMAX
= 125°C,
θ
JA
= 38°C/W
EXPOSED PAD (PIN 21) IS PGND2/GNDD, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LTC3417AEDHC#PBF
LTC3417AEFE#PBF
LTC3417AIFE#PBF
TAPE AND REEL
LTC3417AEDHC#TRPBF
LTC3417AEFE#TRPBF
LTC3417AIFE#TRPBF
PART MARKING
3417A
LTC3417AEFE
LTC3417AIFE
PACKAGE DESCRIPTION
16-Lead (3mm
×
3mm) Plastic DFN
20-Lead Plastic TSSOP
20-Lead Plastic TSSOP
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
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/
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V unless otherwise specified. (Note 2)
SYMBOL
V
IN1
, V
IN2
I
FB1
, I
FB2
V
FB1
, V
FB2
∆V
LINEREG
V
LOADREG
g
m(EA)
PARAMETER
Operating Voltage Range
Feedback Pin Input Current
Feedback Voltage
Reference Voltage Line Regulation. %/V is the
Percentage Change in V
OUT
with a Change in V
IN
Output Voltage Load Regulation
Error Amplifier Transconductance
CONDITIONS
V
IN1
= V
IN2
(Note 3)
(Note 3)
V
IN
= 2.25V to 5V (Note 3)
I
TH1
, I
TH2
= 0.36V (Note 3)
I
TH1
, I
TH2
= 0.84V (Note 3)
I
TH1
, I
TH2(PINLOAD)
= ±5µA (Note 3)
●
elecTrical characTerisTics
MIN
2.25
0.784
TYP
MAX
5.5
± 0.1
UNITS
V
µA
V
%/V
%
%
µS
3417afc
0.8
0.04
0.02
–0.02
1400
0.816
0.2
0.2
–0.2
2
LTC3417A
elecTrical characTerisTics
SYMBOL
I
S
PARAMETER
Input DC Supply Current (Note 4)
Active Mode
Half Active Mode (V
RUN2
= 0V, 1.5A Only)
Half Active Mode (V
RUN1
= 0V, 1A Only)
Both Channels in Sleep Mode
Shutdown
f
OSC
I
LIM1
I
LIM2
R
DS(ON)1
R
DS(ON)2
I
SW1(LKG)
I
SW2(LKG)
V
UVLO
T
PGOOD
R
PGOOD
V
RUN1
, V
RUN2
V
PHASE
I
RUN1
, I
RUN2
,
I
PHASE
,
I
SYNC/MODE
Oscillator Frequency
Peak Switch Current Limit on SW1 (1.5A)
Peak Switch Current Limit on SW2 (1A)
SW1 Top Switch On-Resistance (1.5A)
SW1 Bottom Switch On-Resistance
SW2 Top Switch On-Resistance (1A)
SW2 Bottom Switch On-Resistance
Switch Leakage Current SW1 (1.5A)
Switch Leakage Current SW2 (1A)
Undervoltage Lockout Threshold
Threshold for Power Good. Percentage
Deviation from V
FB
Steady State
(Typically 0.8V)
Power Good Pull-Down On-Resistance
RUN1, RUN2 Threshold
PHASE Threshold High-CMOS Levels
PHASE Threshold Low-CMOS Levels
RUN1, RUN2, PHASE and SYNC/MODE
Leakage Current
V
IN
= 6V, V
PVIN
= 3V
0.01
0.3
V
IN
–0.5
0.5
1
0.5
V
IN
–0.5
V
IN
–0.5
V
IN1
= 3.6V (Note 5)
V
IN1
= 3.6V (Note 5)
V
IN2
= 3.6V (Note 5)
V
IN2
= 3.6V (Note 5)
V
IN1
= 6V, V
ITH1
= 0V, V
RUN1
= 0V
V
IN2
= 6V, V
ITH2
= 0V, V
RUN2
= 0V
V
IN1
, V
IN2
Ramping Down
V
IN1
, V
IN2
Ramping Up
V
FB1
or V
FB2
Ramping Up, V
SYNC/MODE
= 0V
V
FB1
or V
FB2
Ramping Down,
V
SYNC/MODE
= 0V
1.9
1.95
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V unless otherwise specified. (Note 2)
CONDITIONS
V
FB1
= V
FB2
= 0.75V, V
SYNC/MODE
= V
IN
,
V
RUN1
= V
RUN2
= V
IN
V
FB1
= 0.75V, V
SYNC/MODE
= V
IN
, V
RUN1
= V
IN
V
FB2
= 0.75V, V
SYNC/MODE
= V
IN
, V
RUN2
= V
IN
V
FB1
= V
FB2
= 1V, V
SYNC/MODE
= V
IN
,
V
RUN1
= V
RUN2
= V
IN
V
RUN1
= V
RUN2
= 0V
V
FREQ
= V
IN
V
FREQ
: R
T
= 143k
V
FREQ
: Resistor (Note 6)
1.2
0.85
2.1
1.4
MIN
TYP
400
260
260
125
0.1
1.5
1
2.5
1.7
0.088
0.084
0.16
0.15
0.01
0.01
2.07
2.12
–6
–6
160
0.85
300
1.5
1
1
2.2
2.25
MAX
600
400
400
250
1
1.8
1.25
4
UNITS
µA
µA
µA
µA
µA
MHz
MHz
MHz
A
A
Ω
Ω
Ω
Ω
µA
µA
V
V
%
%
Ω
V
V
V
µA
V
V
V
VTL
SYNC/MODE
SYNC/MODE Threshold Voltage Low
VTH
SYNC/MODE
SYNC/MODE Threshold Voltage High
VTH
FREQ
FREQ Threshold Voltage High
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 LTC3417AE is guaranteed to meet specified performance from
0°C to 85°C. Specifications over the –40°C to 85°C operating ambient
temperature range are assured by design, characterization and correlation
with statistical process controls. The LTC3417AI is guaranteed to meet
performance specifications over the –40°C to 85°C operating temperature
range.
Note 3:
The LTC3417A is tested in feedback loop which servos V
FB1
to the
midpoint for the error amplifier (V
ITH1
= 0.6V) and V
FB2
to the midpoint for
the error amplifier (V
ITH2
= 0.6V).
Note 4:
Total supply current is higher due to the internal gate charge being
delivered at the switching frequency.
Note 5:
Switch on-resistance is guaranteed by design and test correlation
on the DHC package and by final test correlation on the FE package.
Note 6:
Variable frequency operation with resistor is guaranteed by design
but not production tested and is subject to duty cycle limitations.
Note 7:
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
Note 8:
T
J
is calculated from the ambient temperature, T
A
, and power dis-
sipation, P
D
, according to the following formula:
LTC3417AEDHC: T
J
= T
A
+ (P
D
• 43°C/W)
LTC3417AEFE: T
J
= T
A
+ (P
D
• 38°C/W)
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3
LTC3417A
Typical perForMance characTerisTics
OUT1 Burst Mode Operation
V
OUT
20mV/DIV
V
OUT
20mV/DIV
OUT1 Pulse Skipping
Mode Operation
V
OUT
20mV/DIV
OUT1 Forced Continuous
Mode Operation
I
L
250mA/DIV
I
L
250mA/DIV
I
L
250mA/DIV
2µs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 100mA
REFER TO FIGURE 4
3417 G01
2µs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 100mA
REFER TO FIGURE 4
3417 G02
2µs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 100mA
REFER TO FIGURE 4
3417 G03
OUT2 Burst Mode Operation
OUT2 Pulse Skipping
Mode Operation
OUT2 Forced Continuous
Mode Operation
V
OUT
20mV/DIV
V
OUT
20mV/DIV
V
OUT
20mV/DIV
I
L
250mA/DIV
I
L
250mA/DIV
I
L
250mA/DIV
2µs/DIV
V
IN
= 3.6V
V
OUT
= 2.5V
I
LOAD
= 60mA
REFER TO FIGURE 4
3417 G04
2µs/DIV
V
IN
= 3.6V
V
OUT
= 2.5V
I
LOAD
= 60mA
REFER TO FIGURE 4
3417 G05
2µs/DIV
V
IN
= 3.6V
V
OUT
= 2.5V
I
LOAD
= 60mA
REFER TO FIGURE 4
3417 G06
OUT1 Efficiency vs Load Current
100
V
IN
= 2.5V
V
OUT
= 1.8V
95
90
EFFICIENCY (%)
EFFICIENCY (%)
85
80
75
70
65
60
0.001
0.01
0.1
Burst Mode
OPERATION
PULSE SKIP
FORCED
CONTINUOUS
REFER TO FIGURE 4
1
10
3417 G07
OUT2 Efficiency vs Load Current
100
V
IN
= 3.6V
V
OUT
= 2.5V
95
90
85
80
75
70
65
60
0.001
0.01
0.1
Burst Mode
OPERATION
PULSE SKIP
FORCED
CONTINUOUS
REFER TO FIGURE 4
1
10
3417 G08
OUT1 Efficiency vs V
IN
(Burst Mode Operation)
100
95
EFFICIENCY (%)
90
85
80
75
70
REFER TO FIGURE 4
2
2.5
3
3.5
4
4.5
5
5.5
3417 G09
V
OUT
= 1.8V
I
LOAD
= 460mA
I
LOAD
= 1.4A
LOAD CURRENT (A)
LOAD CURRENT (A)
V
IN
(V)
3417afc
4
LTC3417A
Typical perForMance characTerisTics
OUT2 Efficiency vs V
IN
(Pulse Skipping Mode)
100
I
LOAD
= 250mA
95
EFFICIENCY (%)
90
85
80
75
70
I
LOAD
= 800mA
V
OUT1
100mV/DIV
V
OUT2
100mV/DIV
Load Step OUT1
Load Step OUT2
I
OUT1
500mA/DIV
I
OUT2
500mA/DIV
V
OUT
= 2.5V
REFER TO FIGURE 4
2
2.5
3
3.5
4
4.5
5
5.5
V
IN
(V)
3417 G10
V
IN
= 3.6V
100µs/DIV
V
OUT
= 1.8V
I
LOAD
= 0.25A to 1.4A
REFER TO FIGURE 4
3417 G11
V
IN
= 3.6V
100µs/DIV
V
OUT
= 2.5V
I
LOAD
= 0.25A to 0.8A
REFER TO FIGURE 4
3417 G12
Efficiency vs Frequency OUT1
94
92
EFFICIENCY (%)
90
88
86
84
82
T
A
= 27°C
V
IN
= 3.6V
V
OUT
= 1.8V
I
OUT
= 300mA
EFFICIENCY (%)
90
85
80
75
70
65
60
Efficiency vs Frequency OUT2
0.105
R
DS(ON)
vs V
IN
OUT1
T
A =
27°C
0.100
P-CHANNEL SWITCH
R
DS(ON)
( )
T
A
= 27°C
V
IN
= 3.6V
V
OUT
= 2.5V
I
OUT
= 100mA
0
1
2
FREQUENCY (MHz)
3
4
3417 G14
0.095
0.090
0.085
N-CHANNEL SWITCH
0.080
2
2.5
3
3.5
4
4.5
5
5.5
0
1
2
3
4
5
3417 G13
FREQUENCY (MHz)
V
IN
(V)
3417 G15
0.20
0.19
0.18
R
DS(ON)
( )
0.17
0.16
0.15
R
DS(ON)
vs V
IN
OUT2
T
A
= 27°C
FREQUENCY VARIATION (%)
6
4
P-CHANNEL SWITCH
2
0
–2
–4
–6
–8
4
4.5
5
5.5
–10
Frequency vs V
IN
Frequency vs Temperature
15
10
5
0
FREQ = 143k TO GROUND
–5
–10
–15
–50 –25
FREQ = V
IN
FREQ = 143k TO GROUND
FREQ = V
IN
N-CHANNEL SWITCH
0.14
2
2.5
3
3.5
FREQUENCY VARIATION (%)
2
2.5
3
3.5
4
4.5
5
5.5
3417 G17
0
25
50
75
100
125
V
IN
(V)
3417 G16
V
IN
(V)
TEMPERATURE (˚C)
3417 G18
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