Linear LTC3417A-1 User Manual
LTC3417A-1
Dual Synchronous
1.5A/1A 4MHz Step-Down
DC/DC Regulator with POR
FEATURES
n
High Effi ciency: Up to 95%
n
1.5A/1A Guaranteed Minimum Output Current
n
Synchronizable to External Clock
n
Power-On-Reset Output
n
No Schottky Diodes Required
n
Programmable Frequency Operation: 1.5MHz or
Adjustable From 0.6MHz to 4MHz
n
Low Ripple (< 35mV
n
Low R
n
Short-Circuit Protected
n
VIN: 2.25V to 5.5V
n
Current Mode Operation for Excellent Line and Load
Internal Switches
DS(ON)
) BurstMode® Operation
P-P
Transient Response
n
125µA Quiescent Current in Sleep Mode
n
Ultralow Shutdown Current: IQ < 1µA
n
Low Dropout Operation: 100% Duty Cycle
n
Phase Pin Selects 2nd Channel Phase Relationship
with Respect to 1st Channel
n
Internal Soft-Start with Individual Run Pin Control
n
Available in Small Thermally Enhanced
(3mm × 5mm) DFN and 20-Lead TSSOP Packages
APPLICATIONS
n
GPS/Navigation Systems
n
Automotive Instrumentation
n
PC Cards
n
Industrial Power Supplies
n
General Purpose Point of Load DC/DC
DESCRIPTION
The LTC®3417A-1 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
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
the need for external Schottky diodes.
The open drain POR pin goes low when either output
voltage falls 6% below regulation. The output will remain
low 150ms longer than the duration of the out of regulation condition.
A user selectable mode input allows the user to trade
off ripple voltage for light load effi ciency. Burst Mode
operation provides high effi ciency 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
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
100µA. In shutdown, the device draws <1µA.
L, LT, LTC and LTM and Burst Mode are registered 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.
power switches provide high effi ciency without
DS(ON)
and thus lower stress on the input capacitor.
IN
TYPICAL APPLICATION
V
IN
2.5V TO 5.5V
V
OUT1
1.8V
1.5A
47μF
10μF
1.5µH
22pF
V
IN
511k
412k
5.9k 2.87k
2200pF
FREQ
SW1
RUN1
V
FB1
I
TH1
V
IN
LTC3417A-1
GND
POR
SW2
RUN2
V
I
FB2
TH2
100k
2.2µH
V
IN
6800pF
3417A-1 TA01
412k
RESET
22pF
866k
V
2.5V
1A
22µF
OUT2
OUT2 Effi ciency
(Burst Mode Operation)
100
REFER TO FIGURE 4
95
EFFICIENCY
90
85
EFFICIENCY (%)
80
75
70
0.001
POWER LOSS
0.01 0.1 1
LOAD CURRENT (A)
VIN = 3.6V
= 2.5V
V
OUT
FREQ = 1MHz
3417A-1 TA01a
10
1
POWER LOSS (W)
0.1
0.01
0.001
0.0001
3417a1fa
1
LTC3417A-1
ABSOLUTE MAXIMUM RATINGS
V
, V
IN1
Voltages ...................................... – 0.3V to 6V
IN2
SYNC/MODE, SW1, SW2, RUN1,
, V
RUN2, V
, I
I
TH1
TH2
– V
V
IN1
FB1
Voltages........ –0.3V to ((V
IN2
, PHASE, FREQ,
FB2
, V
– V
IN2
or V
IN1
.......................................... 0.3V
IN1
) + 0.3V)
IN2
PIN CONFIGURATION
TOP VIEW
1
RUN1
2
V
IN1
3
I
TH1
4
V
FB1
5
V
FB2
I
6
TH2
7
RUN2
8
V
IN2
16-LEAD (5mm × 3mm) PLASTIC DFN
EXPOSED PAD (PIN 17) IS PGND2/GNDD
DHC PACKAGE
T
= 125°C, θJA = 43°C/ W
JMAX
MUST BE SOLDERED TO PCB
16
PGND1
15
SW1
14
PHASE
13
12
11
10
9
GNDA
FREQ
POR
SW2
SYNC/MODE
17
(Note 1)
POR Voltage ................................................ –0.3V to 6V
Operating Temperature Range (Note 2)
LTC3417AE-1 ...................................... –40°C to 85°C
LTC3417AI-1 ..................................... –40°C to 125°C
Junction Temperature (Notes 7, 8) ...................... 125°C
Storage Temperature Range ...................–65°C to 150°C
TOP VIEW
1
GNDD
2
RUN1
3
V
IN1
4
I
TH1
5
V
FB1
V
FB2
I
TH2
RUN2
V
IN2
PGND2
20-LEAD PLASTIC TSSOP
T
JMAX
EXPOSED PAD (PIN 21) IS PGND2/GNDD
MUST BE SOLDERED TO PCB
21
6
7
8
9
10
FE PACKAGE
= 125°C, θJA = 38°C/ W
GNDD
20
PGND1
19
SW1
18
PHASE
17
GNDA
16
FREQ
15
POR
14
SW2
13
SYNC/MODE
12
PGND2
11
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3417AEDHC-1#PBF LTC3417AEDHC-1#TRPBF 3417A1 16-Lead (3mm × 5mm) Plastic DFN –40°C to 85°C
LTC3417AIDHC-1#PBF LTC3417AIDHC-1#TRPBF 3417A1 16-Lead (3mm × 5mm) Plastic DFN –40°C to 125°C
LTC3417AEFE-1#PBF LTC3417AEFE-1#TRPBF LTC3417AFE-1 20-Lead Plastic TSSOP –40°C to 85°C
LTC3417AIFE-1#PBF LTC3417AIFE-1#TRPBF LTC3417AFE-1 20-Lead Plastic TSSOP –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/
The l denotes the specifi cations which apply over the full operating
ELECTRICAL CHARACTERISTICS
temperature range, otherwise specifi cations are at T
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
I
IN1
FB1
, V
IN2
, I
FB2
Operating Voltage Range V
Feedback Pin Input Current VIN = 6V Pin Under Test = 3V ± 0.1 µA
2
= 25°C. VIN = 3.6V unless otherwise specifi ed (Note 2).
A
IN1
= V
IN2
2.25 5.5 V
3417a1fa
LTC3417A-1
The l denotes the specifi cations which apply over the full operating
ELECTRICAL CHARACTERISTICS
temperature range, otherwise specifi cations are at T
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
, V
V
FB1
FB2
ΔV
LINEREG
ΔV
LOADREG
g
m(EA)
I
S
I
S
f
OSC
I
LIM1
I
LIM2
R
DS(ON)1
R
DS(ON)2
I
SW1(LKG)
I
SW2(LKG)
V
UVLO
V
TH(POR)
R
POR
t
POR
V
RUN1, VRUN2
V
PHASE
I
RUN1, IRUN2, IPHASE,
I
SYNC/MODE
VTL
SYNC/MODE
VTH
SYNC/MODE
VTH
FREQ
Feedback Voltage (Note 3)
Reference Voltage Line Regulation. %/V
is the Percentage Change in V
Change in V
IN
OUT
Output Voltage Load Regulation I
Error Amplifi er Transconductance I
Input DC Supply Current (Note 4)
Active Mode V
Half Active Mode (V
Half Active Mode (V
= 0V, 1.5A Only) V
RUN2
= 0V, 1A Only) V
RUN1
Both Channels in Sleep Mode V
Shutdown V
Oscillator Frequency V
Peak Switch Current Limit on SW1 (1.5A) 2.1 2.5 A
Peak Switch Current Limit on SW2 (1A) 1.4 1.7 A
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) V
Switch Leakage Current SW2 (1A) V
Undervoltage Lockout Threshold V
Power-On-Reset Threshold
Percentage Deviation of V
Voltage from
FB
Steady State Value (Typically 0.8V)
Power-On-Reset Pull Down On-Resistance 120 300
Power-On-Reset De-Assertion Delay from
Fault Removal
RUN1, RUN2 Threshold 0.3 0.85 1.5 V
PHASE Threshold High-CMOS Levels V
PHASE Threshold Low-CMOS Levels 0.5 V
RUN1, RUN2, PHASE and SYNC/MODE
Leakage Current
SYNC/MODE Threshold Voltage Low 0.5 V
SYNC/MODE Threshold Voltage High V
FREQ Threshold Voltage High V
= 25°C. VIN = 3.6V unless otherwise specifi ed (Note 2).
A
VIN = 2.25V to 5V (Note 3) 0.02 0.2 %/V
with a
, I
= 0.36V (Note 3)
TH1
TH2
I
, I
= 0.84V (Note 3)
TH1
TH2
, I
TH1
TH2(PINLOAD)
= V
FB1
FB2
V
= V
RUN1
= 0.75V, V
FB1
= 0.75V, V
FB2
= V
FB1
FB2
V
= V
RUN2
= V
RUN1
= V
FREQ
V
: RT = 143k
FREQ
V
: Resistor (Note 6)
FREQ
V
= 3.6V (Note 5)
IN1
V
= 3.6V (Note 5)
IN1
V
= 3.6V (Note 5)
IN2
V
= 3.6V (Note 5)
IN2
= 6V, V
IN1
= 6V, V
IN2
, V
IN1
IN2
V
, V
IN1
IN2
or V
V
FB1
FB2
or V
V
FB1
FB2
FREQ = V
= ±5µA (Note 3) 1400 µS
= 0.75V, V
RUN2
= 1V, V
IN
RUN2
IN
RUN1
RUN2
SYNC/MODE
= V
IN
SYNC/MODE
SYNC/MODE
SYNCMODE
= 0V 0.01 1 µA
= 0V 0.01 1 µA
= 0V 0.01 1 µA
= VIN, V
= VIN, V
= VIN, V
= VIN,
RUN1
RUN2
RUN1
= V
= V
IN
IN
=
Ramping Down
Ramping Up
Ramping Up –6 %
Ramping Down –8 %
IN
FREQ Tied to GND Through 143k Resistor 294,912 Clock
VIN = 6V, Pin Under Test = 3V ±0.01 ±1 µA
l
0.784 0.8 0.816 V
0.02
–0.02
–0.2
400 600 µA
260 400 µA
260 400 µA
125 250 µA
1.2
0.85
1.5
1
1.25
0.088
0.084
0.16
0.15
1.9
1.95
2.07
2.12
2.25
212,992 Clock
–0.5 V
IN
–0.5 V
IN
–0.5 V
IN
0.2
1.8
4
2.2
%
%
MHz
MHz
MHz
Cycles
Cycles
V
V
3417a1fa
3
LTC3417A-1
ELECTRICAL CHARACTERISTICS
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-1 is guaranteed to meet specifi ed performance
from 0°C to 85°C. Specifi cations over the –40°C to 85°C operating
ambient temperature range are assured by design, characterization
and correlation with statistical process controls. The LTC3417AI-1 is
guaranteed to meet performance specifi cations over the –40°C to 125°C
operating temperature range.
Note 3: The LTC3417A-1 is tested in feedback loop which servos V
the midpoint for the error amplifi er (V
for the error amplifi er (V
ITH2
= 0.6V).
= 0.6V) and V
ITH1
to the midpoint
FB2
FB1
to
Note 4: Total supply current is higher due to the internal gate charge being
Note 5: Switch on-resistance is guaranteed by design and test correlation
on the DHC package and by fi nal 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 specifi ed maximum operating junction
temperature may impair device reliability.
Note 8: T
J
dissipation, P
LTC3417AEDHC-1: T
LTC3417AEFE-1: T
delivered at the switching frequency.
TYPICAL PERFORMANCE CHARACTERISTICS
OUT1 Pulse Skipping
Mode Operation
V
OUT
V
OUT
20mV/DIV
OUT1 Burst Mode Operation
20mV/DIV
is calculated from the ambient temperature, TA, and power
, according to the following formula:
D
= TA + (PD • 43°C/W)
J
= TA + (PD • 38°C/W)
J
OUT1 Forced Continuous
Mode Operation
V
OUT
20mV/DIV
250mA/DIV
V
OUT
20mV/DIV
250mA/DIV
I
L
VIN = 3.6V
= 1.8V
V
OUT
= 100mA
I
LOAD
REFER TO FIGURE 4
2µs/DIV
OUT2 Burst Mode Operation
I
L
VIN = 3.6V
= 2.5V
V
OUT
= 60mA
I
LOAD
REFER TO FIGURE 4
2µs/DIV
3417A-1 G01
3417A-1 G04
250mA/DIV
V
OUT
20mV/DIV
250mA/DIV
I
L
VIN = 3.6V
= 1.8V
V
OUT
= 100mA
I
LOAD
REFER TO FIGURE 4
2µs/DIV
OUT2 Pulse Skipping
Mode Operation
I
L
VIN = 3.6V
= 2.5V
V
OUT
= 60mA
I
LOAD
REFER TO FIGURE 4
2µs/DIV
3417A-1 G02
3417A-1 G05
250mA/DIV
V
20mV/DIV
250mA/DIV
I
L
VIN = 3.6V
= 1.8V
V
OUT
= 100mA
I
LOAD
REFER TO FIGURE 4
2µs/DIV
OUT2 Forced Continuous
Mode Operation
OUT
I
L
VIN = 3.6V
= 2.5V
V
OUT
= 60mA
I
LOAD
REFER TO FIGURE 4
2µs/DIV
3417A-1 G03
3417A-1 G06
3417a1fa
4
TYPICAL PERFORMANCE CHARACTERISTICS
LTC3417A-1
OUT1 Effi ciency vs V
OUT1 Effi ciency vs Load Current
100
VIN = 2.5V
= 1.8V
V
OUT
95
90
85
80
75
EFFICIENCY (%)
70
65
60
0.001 0.1 1 10
REFER TO FIGURE 4
0.01
LOAD CURRENT (A)
OUT2 Effi ciency vs V
Burst Mode
OPERATION
PULSE SKIP
FORCED
CONTINUOUS
IN
3417A-1 G07
OUT2 Effi ciency vs Load Current
100
VIN = 3.6V
= 2.5V
V
OUT
95
90
85
80
75
EFFICIENCY (%)
70
65
60
0.001 0.1 1 100.01
REFER TO FIGURE 4
LOAD CURRENT (A)
Burst Mode
OPERATION
PULSE SKIP
FORCED
CONTINUOUS
3417A-1 G08
(Burst Mode Operation)
100
V
= 1.8V
OUT
95
90
85
EFFICIENCY (%)
80
75
70
2 2.5 3.5 4.5 5.5
(Pulse Skipping Mode) Load Step OUT1 Load Step OUT2
100
I
= 250mA
I
LOAD
LOAD
= 800mA
V
OUT1
100mV/DIV
V
OUT2
100mV/DIV
95
90
I
LOAD
3
IN
I
= 460mA
LOAD
= 1.4A
REFER TO FIGURE 4
45
VIN (V)
3417A-1 G09
85
EFFICIENCY (%)
80
75
70
2 2.5
3 3.5
V
= 2.5V
OUT
REFER TO FIGURE 4
4 4.5 5
VIN (V)
3417A-1 G10
I
OUT1
500mA/DIV
VIN = 3.6V
= 1.8V
V
OUT
= 0.25A to 1.4A
I
LOAD
REFER TO FIGURE 4
100µs/DIV
3417A-1 G11
Effi ciency vs Frequency OUT1 Effi ciency vs Frequency OUT2 R
94
92
90
88
EFFICIENCY (%)
86
84
82
0
TA = 27°C
= 3.6V
V
IN
= 1.8V
V
OUT
= 300mA
I
OUT
1234
FREQUENCY (MHz)
3417A-1 G13
5
90
85
80
75
EFFICIENCY (%)
70
65
60
0
TA = 27°C
= 3.6V
V
IN
= 2.5V
V
OUT
= 100mA
I
OUT
12 3
FREQUENCY (MHz)
3417A-1 G14
I
OUT2
500mA/DIV
0.105
0.100
0.095
(Ω)
DS(ON)
0.090
R
0.085
0.080
VIN = 3.6V
= 2.5V
V
OUT
= 0.25A to 0.8A
I
LOAD
REFER TO FIGURE 4
vs VIN OUT1
DS(ON)
P-CHANNEL SWITCH
N-CHANNEL SWITCH
2 2.5
3
100µs/DIV
4
3.5
VIN (V)
4.5
T
A =
3417A-1 G12
27°C
5
3417A-1 G15
5.5
3417a1fa
5
LTC3417A-1
TYPICAL PERFORMANCE CHARACTERISTICS
R
0.20
0.19
0.18
(Ω)
0.17
DS(ON)
R
0.16
0.15
0.14
2
PIN FUNCTIONS
vs VIN OUT2 Frequency vs V
DS(ON)
P-CHANNEL SWITCH
N-CHANNEL SWITCH
2.5 3
4 5 5.5
3.5 4.5
VIN (V)
TA = 27°C
3417A-1 G16
6
4
2
FREQ = 143k TO GROUND
0
–2
–4
–6
FREQUENCY VARIATION (%)
–8
–10
2
(DFN/TSSOP)
FREQ = V
2.5 3
RUN1 (Pin 1/Pin 2): Enable for 1.5A Regulator. When
at Logic 1, 1.5A regulator is running. When at 0V, 1.5A
regulator is off. When both RUN1 and RUN2 are at 0V, the
part is in shutdown.
(Pin 2/Pin 3): Supply Pin for P-Channel Switch of
V
IN1
1.5A Regulator.
(Pin 3/Pin 4): Error Amplifi er Compensation Point
I
TH1
for 1.5A Regulator. The current comparator threshold
increases with this control voltage. Nominal voltage range
for this pin is 0V to 1.5V.
(Pin 4/Pin 5): Receives the feedback voltage from
V
FB1
external resistive divider across the 1.5A regulator output.
Nominal voltage for this pin is 0.8V.
(Pin 5/Pin 6): Receives the feedback voltage from
V
FB2
external resistive divider across the 1A regulator output.
Nominal voltage for this pin is 0.8V.
(Pin 6/Pin 7): Error Amplifi er Compensation Point for
I
TH2
1A regulator. The current comparator threshold increases
with this control voltage. Nominal voltage range for this
pin is 0V to 1.5V.
RUN2 (Pin 7/Pin 8): Enable for 1A Regulator. When at
Logic 1, 1A regulator is running. When at 0V, 1A regulator is off. When both RUN1 and RUN2 are at 0V, the part
is in shutdown.
(Pin 8/Pin 9): Supply Pin for P-Channel Switch of 1A
V
IN2
Regulator and Supply for Analog Circuitry.
Frequency vs Temperature
15
10
5
0
–5
FREQUENCY VARIATION (%)
–10
–15
–50
–25 0
25 75
TEMPERATURE (°C)
FREQ = V
IN
FREQ = 143k TO GROUND
50 100 125
3417A-1 G18
3.5
IN
IN
4 4.5
(V)
V
IN
5 5.5
3417A-1 G17
SYNC/MODE (Pin 9/Pin 12): Combination Mode Selection
and Oscillator Synchronization Pin. This pin controls the operation of the device. When the voltage on the SYNC/MODE
pin is >(V
– 0.5V), Burst Mode operation is selected.
IN
When the voltage on the SYNC/MODE pin is <0.5V, pulse
skipping mode is selected. When the SYNC/MODE pin is
held at V
/2, forced continuous mode is selected. The
IN
oscillation frequency can be synchronized to an external
oscillator applied to this pin. When synchronized to an
external clock, pulse skip mode is selected.
SW2 (Pin 10/Pin 13): Switch Node Connection to the
Inductor for the 1A Regulator. This pin swings from V
IN2
to PGND2.
POR (Pin 11/Pin 14): The Power-On-Reset Pin. This
open drain-logic output is pulled to GND when the output
voltage of either regulator falls 8% below regulation and
goes high approximately 150ms after both regulators are
above –6% of regulation. If either RUN1 or RUN2 is low
(the respective regulator is in sleep mode and therefore
the output voltage is low), then POR refl ects the regulation
of the running regulator.
FREQ (Pin 12/Pin 15): Frequency Set Pin. When FREQ is
, internal oscillator runs at 1.5MHz. When a resistor
at V
IN
is connected from this pin to ground, the internal oscillator
frequency can be varied from 0.6MHz to 4MHz.
GNDA (Pin 13/Pin 16): Analog Ground Pin for Internal
Analog Circuitry.
3417a1fa
6
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