LTC3416
4A, 4MHz, Monolithic
Synchronous Step-Down
Regulator with Tracking
FEATURES
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DESCRIPTIO
High Efficiency: Up to 95%
4A Output Current
Low R
DS(ON)
Internal Switch: 67mΩ
Tracking Input to Provide Easy Supply Sequencing
Programmable Frequency: 300kHz to 4MHz
2.25V to 5.5V Input Voltage Range
±2%
Output Voltage Accuracy
0.8V Reference Allows Low Output Voltage
Low Dropout Operation: 100% Duty Cycle
Power Good Output Voltage Monitor
Overtemperature Protected
Available in a 20-Lead Thermally Enhanced
TSSOP Package
The LTC
®
3416 is a high efficiency monolithic synchro-
nous, step-down DC/DC converter utilizing a constant
frequency, current mode architecture. It operates from an
input voltage range of 2.25V to 5.5V and provides a
regulated output voltage from 0.8V to 5V while delivering
up to 4A of output current. The internal synchronous
power switch with 67mΩ of on-resistance increases effi-
ciency and eliminates the need for an external Schottky
diode. Switching frequency is set by an external resistor.
100% duty cycle provides low dropout operation extend-
ing battery life in portable systems. OPTI-LOOP
®
compen-
sation allows the transient response to be optimized over
a wide range of loads and output capacitors.
The LTC3416 operates in forced continuous operation and
provides tracking of another power supply rail. Forced
continuous operation reduces noise and RF interference and
provides excellent transient response. Fault protection is
provided by an overcurrent comparator, and adjustable
compensation allows the transient response to be optimized
over a wide range of loads and output capacitors.
, LTC and LT are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. OPTI-LOOP is a registered trade-
mark of Linear Technology Corporation. Protected by U.S. Patents including 5481178,
6580258, 6304066, 6127815, 6498466, 6611131, 6724174.
APPLICATIO S
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Portable Instruments
Notebook Computers
Distributed Power Systems
Battery-Powered Equipment
POL Board Power
TYPICAL APPLICATIO
I/O VOLTAGE
V
IN
2.5V TO 5.5V
SVIN
R
T
127k
V
OUT2
2.5V
100
90
22µF
PVIN
PGOOD
SW
LTC3416
RUN/SS PGND
I
TH
SGND
7.5k
820pF
255k
200k
255k
3416 F01a
80
EFFICIENCY (%)
0.2µH
100µF
×2
V
OUT1
1.8V
4A
70
60
50
40
30
20
10
0
0.01
TRACK
V
FB
200k
Figure 1a. 2.5V/4A Step-Down Regulator with Tracking
Figure 1b. Efficiency vs Load Current
3416fa
U
V
IN
= 2.5V
V
IN
= 3.3V
V
OUT
= 1.8V
f = 2MHz
0.10
1
LOAD CURRENT (A)
10
3416 G09
U
U
1
LTC3416
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
PGND
R
T
TRACK
RUN/SS
SGND
NC
PV
IN
SW
SW
1
2
3
4
5
6
7
8
9
21
20 PGND
19 V
FB
18 I
TH
17 PGOOD
16 SV
IN
15 NC
14 PV
IN
13 SW
12 SW
11 PGND
Input Supply Voltage .................................. – 0.3V to 6V
I
TH
, RUN, V
FB
Voltages .............................. – 0.3V to V
IN
TRACK Voltage .......................................... – 0.3V to V
IN
SW Voltage .................................. – 0.3V to (V
IN
+ 0.3V)
Operating Ambient Temperature Range
(Note 2) .................................................. – 40°C to 85°C
Junction Temperature (Notes 5, 6) ...................... 125°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER PART
NUMBER
LTC3416EFE
PGND 10
FE PACKAGE
20-LEAD PLASTIC TSSOP
T
JMAX
= 125°C,
θ
JA
= 38°C/W,
θ
JC
= 10°C/W
EXPOSED PAD IS GND (PIN 21)
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
SYMBOL
V
IN
V
FB
I
FB
I
TRACK
∆V
FB
V
TRACK
V
LOADREG
∆V
PGOOD
R
PGOOD
I
Q
PARAMETER
Input Voltage Range
Regulated Feedback Voltage
Feedback Input Current
TRACK Input Current
Reference Voltage Line Regulation
Tracking Voltage Offset
Tracking Voltage Range
Output Voltage Load Regulation
Power Good Range
Power Good Resistance
Input DC Bias Current
Active Current
Shutdown
Switching Frequency
Switching Frequency Range
R
DS(ON)
of P-Channel FET
R
DS(ON)
of N-Channel FET
Peak Current Limit
Undervoltage Lockout Threshold
SW Leakage Current
RUN Threshold
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.3V, unless otherwise noted.
CONDITIONS
(Note 3)
●
MIN
2.25
0.784
TYP
0.800
MAX
5.5
0.816
0.2
0.2
UNITS
V
V
µA
µA
%/V
mV
V
%
%
%
Ω
µA
µA
MHz
MHz
mΩ
mΩ
A
V
µA
V
3416fa
V
IN
= 2.5V to 5.5V (Note 3)
V
TRACK
= 0.4V
0
Measured in Servo Loop, V
ITH
= 0.36V
Measured in Servo Loop, V
ITH
= 0.84V
0.04
0.2
30
0.8
0.02
–0.02
±7.5
120
0.2
–0.2
±9
200
350
1
1.12
4.00
100
100
2.25
1
0.8
(Note 4)
V
FB
= 0.7V, V
ITH
= 1.2V
V
RUN
= 0V
R
OSC
= 294kΩ
(Note 4)
I
SW
= 300mA
I
SW
= –300mA
6
1.75
V
RUN
= 0V, V
IN
= 5.5V
0.5
0.88
0.30
300
0.02
1
67
50
8
2
0.1
0.65
f
OSC
R
PFET
R
NFET
I
LIMIT
V
UVLO
I
LSW
V
RUN
2
U
W
U
U
W W
W
LTC3416
ELECTRICAL CHARACTERISTICS
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired. The voltage should never exceed 6.0V for any
pin.
Note 2:
The LTC3416E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 3:
The LTC3416 is tested in a feedback loop that adjusts V
FB
to
achieve a specified error amplifier output voltage (I
TH
).
Note 4:
This parameter is guaranteed by design and characterization.
Note 5:
Dynamic supply current is higher due to the internal gate charge
being delivered at the switching frequency.
Note 6:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
as follows:
LTC3416E: T
J
= T
A
+ (P
D
)(38°C/W)
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.
TYPICAL PERFOR A CE CHARACTERISTICS
V
REF
vs Temperature, V
IN
= 3.3V
0.800
90
80
PFET
0.799
ON-RESISTANCE (mΩ)
ON-RESISTANCE (mΩ)
V
REF
(V)
0.798
0.797
0.796
0.795
–40 –20
0
20 40 60 80 100 120 140
TEMPERATURE (°C)
3416 G01
Switch Leakage vs Input Voltage
20
18
SWITCH LEAKAGE CURRENT (nA)
T
A
= 25°C
16
PFET
12
10
8
6
4
2
0
2.25
NFET
FREQUENCY (kHz)
FREQUENCY (kHz)
14
2.75 3.25 3.75 4.25 4.75
INPUT VOLTAGE (V)
U W
5.25
3416 G04
Switch On-Resistance
vs Input Voltage
T
A
= 25°C
120
100
80
Switch On-Resistance
vs Temperature, V
IN
= 3.3V
70
60
50
40
30
20
NFET
PFET
60
40
20
NFET
10
0
2.25 2.75 3.25 3.75 4.25 4.75 5.25
INPUT VOLTAGE (V)
5.75
0
–40 –25 –10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
3416 G03
3416 G02
Frequency vs R
OSC
7000
6000
5000
4000
3000
2000
1000
0
25 125 225 325 425 525 625 725 825 925
R
OSC
(k)
3416 G05
Frequency vs Input Voltage
1040
V
IN
= 3.3V
T
A
= 25°C
1020
1000
980
960
940
920
900
2.25
R
OSC
= 294k
T
A
= 25°C
2.75 3.25 3.75 4.25 4.75
INPUT VOLTAGE (V)
5.25
3416 G06
3416fa
3
LTC3416
TYPICAL PERFOR A CE CHARACTERISTICS
Frequency vs Temperature
1090
1070
1050
FREQUENCY (kHz)
V
IN
= 3.3V
R
OSC
= 294k
QUIESCENT CURRENT (µA)
250
200
150
100
50
0
2.25
2.75
3.25 3.75 4.25 4.75
INPUT VOLTAGE (V)
5.25
3416 G08
EFFICIENCY (%)
1030
1010
990
970
950
930
910
–40 –20
0
20 40 60 80
TEMPERATURE (°C)
100 120
3416 G07
Efficiency vs Input Voltage
98
96
94
92
EFFICIENCY (%)
90
88
86
84
82
80
78
2.5
3.0
4.0
4.5
3.5
INPUT VOLTAGE (V)
5.0
5.5
3416 G10
∆V
OUT
/V
OUT
(%)
Load Step Transient
V
OUT
INDUCTOR
CURRENT
2A/DIV
V
IN
= 3.3V, V
OUT
= 1.8V
f = 2MHz
LOAD STEP = 0A TO 4A
4
U W
DC Supply Current
vs Input Voltage
400
350
300
100
90
80
70
60
50
40
30
20
10
Efficiency vs Load Current,
Forced Continuous
V
IN
= 2.5V
V
IN
= 3.3V
0
0.01
V
OUT
= 1.8V
f = 2MHz
0.10
1
LOAD CURRENT (A)
10
3416 G09
Load Regulation
0
–0.20
–0.40
–0.60
–0.80
–1.00
–1.20
–1.40
0
0.5
1.0
1.5 2.0 2.5 3.0
LOAD CURRENT (A)
3.5
4.0
V
IN
= 3.3V
V
OUT
= 1.8V
I
OUT
= 1A
V
OUT
= 2.5V
T
A
= 25°C
I
OUT
= 4A
3416 G11
Tracking: Start-Up and Shutdown
20µs/DIV
3416 G12
5ms/DIV
V
IN
= 3.3V, V
OUT
= 1.8V
TRACKING 2.5V
3416 G13
3416fa
LTC3416
PI FU CTIO S
PGND (Pins 1, 10, 11, 20):
Power Ground. Connect this
pin closely to the (–) terminal of C
IN
and C
OUT
.
R
T
(Pin 2):
Oscillator Resistor Input. Connecting a resistor
to ground from this pin sets the switching frequency.
TRACK (Pin 3):
Tracking Voltage Input. Applying a voltage
that is less than 0.8V to this pin enables tracking. During
tracking, the V
FB
pin will regulate to the voltage on this pin.
Do not float this pin.
RUN/SS (Pin 4):
Run Control and Soft-Start Input. Forcing
this pin below 0.5V shuts down the LTC3416. In shutdown
all functions are disabled, drawing <1µA of supply current.
A capacitor to ground from this pin sets the ramp time to
full output current.
SGND (Pin 5):
Signal Ground. All small-signal compo-
nents and compensation components should connect to
this ground, which in turn connects to PGND at one point.
NC (Pins 6, 15):
No Connect.
PV
IN
(Pins 7, 14):
Power Input Supply. Decouple this pin
to PGND with a capacitor.
SW (Pins 8, 9, 12, 13):
Switch Node Connection to
Inductor. This pin connects to the drains of the internal
main and synchronous power MOSFET switches.
SV
IN
(Pin 16):
Signal Input Supply. Decouple this pin to
the SGND capacitor.
PGOOD (Pin 17):
Power Good Output. Open-drain logic
output that is pulled to ground when the output voltage is
not within
±7.5%
of the regulation point.
I
TH
(Pin 18):
Error Amplifier Compensation Point. The
current comparator threshold increases with this control
voltage. Nominal voltage range for this pin is from 0.2V to
1.4V with 0.4V corresponding to the zero-sense voltage
(zero current).
V
FB
(Pin 19):
Feedback Pin. Receives the feedback voltage
from a resistive divider connected across the output.
Exposed Pad (Pin 21):
Ground. Connect to SGND.
U
U
U
3416fa
5
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