LTC3417
Dual Synchronous
1.4A/800mA 4MHz
Step-Down DC/DC Regulator
FEATURES
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DESCRIPTIO
High Efficiency: Up to 95%
1.4A/800mA Guaranteed Minimum Output Current
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
The LTC
®
3417 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 voltage
range and has a constant programmable switching fre-
quency, 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
®
opera-
tion 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 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.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark 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
APPLICATIO S
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PDAs/Palmtop PCs
Digital Cameras
Cellular Phones
PC Cards
Wireless and DSL Modems
TYPICAL APPLICATIO
V
IN
2.5V TO 5.5V
10µF
V
OUT1
1.8V
1.4A
1.5µH
22pF
V
IN
511k
V
FB1
22µF
412k
I
TH1
5.9k
2200pF
GND
FREQ
SW1
RUN1
V
IN
OUT2 Efficiency
(Burst Mode Operation)
100
95
REFER TO FIGURE 4
10
2.2µH
SW2
RUN2
LTC3417
V
FB2
V
IN
866k
412k
I
TH2
2.87k
6800pF
3417 TA01
EFFICIENCY (%)
22pF
V
OUT2
2.5V
800mA
EFFICIENCY
90
0.1
85
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
10µF
U
1
POWER LOSS (W)
U
U
0.001
0.0001
3417fb
1
LTC3417
ABSOLUTE
AXI U
RATI GS
(Note 1)
Operating Ambient Temperature Range
(Note 2) .................................................. – 40°C to 85°C
Junction Temperature (Notes 7, 8) ...................... 125°C
Storage Temperature Range
DFN Package ................................... – 65°C to 125°C
TSSOP Package ............................... – 65°C to 150°C
V
IN1
, V
IN2
Voltages ..................................... – 0.3V to 6V
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
PACKAGE/ORDER I FOR ATIO
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
MODE
ORDER PART
NUMBER
LTC3417EDHC
DHC PART MARKING
3417
DHC PACKAGE
16-LEAD (3mm
×
5mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 43°C/ W
EXPOSED PAD (PIN 17) IS PGND2/GNDD
MUST BE SOLDERED TO PCB
Order Options
Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The
●
denotes 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)
●
●
2
U
U
W
W W
U
W
TOP VIEW
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 MODE
11 PGND2
ORDER PART
NUMBER
LTC3417EFE
PGND2 10
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
MIN
2.25
0.784
TYP
MAX
5.5
±0.1
UNITS
V
µA
V
%/V
%
%
µS
0.8
0.04
0.02
–0.02
1400
0.816
0.2
0.2
–0.2
3417fb
LTC3417
ELECTRICAL CHARACTERISTICS
The
●
denotes 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
I
S
PARAMETER
Input DC Supply Current (Note 4)
Active Mode
Half Active Mode (V
RUN2
= 0V, 1.4A Only)
Both Channels in Sleep Mode
Shutdown
f
OSC
Oscillator Frequency
CONDITIONS
V
FB1
= V
FB2
= 0.75V, V
MODE
= V
IN
,
V
RUN1
= V
RUN2
= V
IN
V
FB1
= 0.75V, V
MODE
= V
IN
, V
RUN1
= V
IN
V
FB1
= V
FB2
= 1V, V
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
1.8
1
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
MODE
= 0V
V
FB1
or V
FB2
Ramping Down, V
MODE
= 0V
1.9
1.95
MIN
TYP
400
260
260
125
0.1
1.5
1
2.25
1.2
0.088
0.084
0.16
0.15
0.01
0.01
2.07
2.12
–6
–6
160
0.3
V
IN
–0.5
0.5
V
IN
= 6V, PV
IN
= 3V
0.01
1
0.5
V
IN
–0.5
V
IN
–0.5
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
Half Active Mode (V
RUN1
= 0V, 800mA Only) V
FB2
= 0.75V, V
MODE
= V
IN
, V
RUN2
= V
IN
I
LIM1
I
LIM2
R
DS(ON)1
R
DS(ON)2
I
SW1(LKG)
I
SW2(LKG)
V
UVLO
T
PGOOD
Peak Switch Current Limit on SW1 (1.4A)
Peak Switch Current Limit on SW2 (800mA)
SW1 Top Switch On-Resistance (1.4A)
SW1 Bottom Switch On-Resistance
SW2 Top Switch On-Resistance (800mA)
SW2 Bottom Switch On-Resistance
Switch Leakage Current SW1 (1.4A)
Switch Leakage Current SW2 (800mA)
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
R
PGOOD
V
RUN1
, V
RUN2
V
PHASE
I
RUN1
, I
RUN2
, RUN1, RUN2, PHASE and MODE
I
PHASE
, I
MODE
Leakage Current
VTL
MODE
VTH
MODE
VTH
FREQ
MODE Threshold Voltage Low
MODE Threshold Voltage High
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 LTC3417 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.
Note 3:
The LTC3417 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
dissipation, P
D
, according to the following formula:
LTC3417EDHC: T
J
= T
A
+ (P
D
• 43°C/W)
LTC3417EFE: T
J
= T
A
+ (P
D
• 38°C/W)
3417fb
3
LTC3417
TYPICAL PERFOR A CE CHARACTERISTICS
OUT1 Burst Mode Operation
OUT1 Pulse Skipping
Mode Operation
OUT1 Forced Continuous
Mode Operation
V
OUT
20mV/DIV
I
L
250mA/DIV
V
IN
= 3.6V
2µs/DIV
V
OUT
= 1.8V
I
LOAD
= 100mA
REFER TO FIGURE 4
OUT2 Burst Mode Operation
V
OUT
20mV/DIV
I
L
250mA/DIV
V
IN
= 3.6V
2µs/DIV
V
OUT
= 2.5V
I
LOAD
= 60mA
REFER TO FIGURE 4
OUT1 Efficiency vs Load Current
100
V
IN
= 2.5V
V
OUT
= 1.8V
95
90
100
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
LOAD CURRENT (A)
3417 G07
85
80
75
70
65
60
0.001
0.01
Burst Mode
OPERATION
PULSE SKIP
FORCED
CONTINUOUS
REFER TO FIGURE 4
0.1
1
LOAD CURRENT (A)
3417 G08
EFFICIENCY (%)
4
U W
V
OUT
20mV/DIV
V
OUT
20mV/DIV
I
L
250mA/DIV
I
L
250mA/DIV
3417 G01
V
IN
= 3.6V
2µs/DIV
V
OUT
= 1.8V
I
LOAD
= 100mA
REFER TO FIGURE 4
3417 G02
V
IN
= 3.6V
2µs/DIV
V
OUT
= 1.8V
I
LOAD
= 100mA
REFER TO FIGURE 4
3417 G03
OUT2 Pulse Skipping
Mode Operation
OUT2 Forced Continuous
Mode Operation
V
OUT
20mV/DIV
V
OUT
20mV/DIV
I
L
250mA/DIV
I
L
250mA/DIV
3417 G04
V
IN
= 3.6V
2µs/DIV
V
OUT
= 2.5V
I
LOAD
= 60mA
REFER TO FIGURE 4
3417 G05
V
IN
= 3.6V
2µs/DIV
V
OUT
= 2.5V
I
LOAD
= 60mA
REFER TO FIGURE 4
3417 G06
OUT2 Efficiency vs Load Current
V
IN
= 3.6V
V
OUT
= 2.5V
95
90
90
100
95
OUT1 Efficiency vs V
IN
(Burst Mode Operation)
V
OUT
= 1.8V
I
LOAD
= 460mA
I
LOAD
= 1.4A
85
80
75
70
2
2.5
3
3.5
REFER TO FIGURE 4
4
4.5
5
5.5
V
IN
(V)
3417 G09
3417fb
LTC3417
TYPICAL PERFOR A CE CHARACTERISTICS
OUT2 Efficiency vs V
IN
(Pulse Skipping Mode)
100
I
LOAD
= 250mA
95
EFFICIENCY (%)
90
85
80
75
70
I
LOAD
= 800mA
V
OUT
= 2.5V
REFER TO FIGURE 4
2
2.5
3
3.5
4
4.5
V
IN
(V)
3417 G10
Efficiency vs Frequency OUT1
94
92
90
88
86
84
82
0
1
2
3
4
5
T
A
= 27°C
V
IN
= 3.6V
V
OUT
= 1.8V
I
OUT
= 300mA
EFFICIENCY (%)
EFFICIENCY (%)
R
DS(ON)
(Ω)
FREQUENCY (MHz)
3417 G13
R
DS(ON)
vs V
IN
OUT2
0.20
0.19
0.18
P-CHANNEL SWITCH
T
A
= 27°C
FREQUENCY VARIATION (%)
2
0
–2
FREQ = 143k TO GROUND
FREQUENCY VARIATION (%)
R
DS(ON)
(Ω)
0.17
0.16
0.15
N-CHANNEL SWITCH
0.14
2
2.5
3
3.5
4
4.5
V
IN
(V)
3417 G16
U W
5
5
Load Step OUT1
Load Step OUT2
V
OUT1
100mV/DIV
V
OUT2
100mV/DIV
I
OUT1
500mA/DIV
I
OUT2
500mA/DIV
5.5
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 OUT2
90
85
80
0.095
0.105
R
DS(ON)
vs V
IN
OUT1
T
A =
27°C
0.100
P-CHANNEL SWITCH
75
70
65
T
A
= 27°C
V
IN
= 3.6V
V
OUT
= 2.5V
I
OUT
= 100mA
0.090
0.085
N-CHANNEL SWITCH
60
0
1
2
3
4
0.080
2
2.5
3
3.5
4
4.5
5
5.5
V
IN
(V)
FREQUENCY (MHz)
3417 G14
3417 G15
Frequency vs V
IN
6
15
10
5
0
Frequency vs Temperature
4
FREQ = V
IN
FREQ = 143k TO GROUND
–4
FREQ = V
IN
–5
–10
–6
–8
5.5
–10
2
2.5
3
3.5
4
4.5
5
5.5
–15
–50
–25
0
25
50
75
100
125
V
IN
(V)
3417 G17
TEMPERATURE (˚C)
3417 G18
3417fb
5
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