FEATURES
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LTC3822-1
No R
SENSE
TM
, Low Input
Voltage, Synchronous
Step-Down DC/DC Controller
DESCRIPTION
The LTC
®
3822-1 is a synchronous step-down switching
regulator controller that drives external N-channel power
MOSFETs using few external components. The constant
frequency current mode architecture with MOSFET V
DS
sensing eliminates the need for sense resistors and im-
proves efficiency.
Burst Mode operation provides high efficiency at light
loads. The 99% maximum duty cycle provides low dropout
operation, extending operating time in battery-powered
systems.
The operating frequency can be programmed up to 750kHz,
allowing the use of small surface mount inductors and ca-
pacitors. For noise sensitive applications, the LTC3822-1
can be synchronized to an external clock from 250kHz to
750kHz.
The LTC3822-1 is available in the tiny footprint thermally
enhanced 12-pin DFN package or 16-pin narrow SSOP
package.
LTC3822-1
LTC3822
Light Load
Continuous, Discontinuous Discontinuous Mode
Operation
or Burst Mode Operation
Package
DD12 (3mm
×
3mm), GN16 DD10 (3mm
×
3mm),
MS10E
Tracking/Soft-Start Yes
Internal Soft-Start Only
External Sync
Yes
No
PGOOD Pin
GN16 Only
No
Dual N-Channel MOSFET Synchronous Drive
No Current Sense Resistor Required
Optimized for 3.3V
IN
and Li-Ion Applications
Constant Frequency Current Mode Operation for
Excellent Line and Load Transient Response
±1% 0.6V Reference
Low Dropout Operation: 99% Duty Cycle
Phase-Lockable or Adjustable Frequency:
250kHz to 750kHz
Internal Soft-Start Circuitry
Tracking and Adjustable Soft-Start Input
Selectable Maximum Peak Current Sense Threshold
Selectable Burst Mode
®
/ Forced Continuous/Pulse
Skipping Mode at Light Load
Digital RUN Control Pin
Output Overvoltage Protection
Micropower Shutdown: I
Q
= 7.5µA
Tiny Thermally Enhanced 12-Pin (3mm
×
3mm) DFN
or 16-Pin Narrow SSOP Packages
APPLICATIONS
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Single Cell Li-Ion Powered Systems
3.3V
IN
Systems
, LT, LTC, LTM 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.
Protected by Patents, including 5481178, 5929620, 6580258, 6304066, 5847554,
6611131, 6498466, 5705919.
TYPICAL APPLICATION
IPRG
RUN
PLLLPF
TG
LTC3822-1
I
TH
SW
10.2k
1nF
BOOST
SYNC/MODE
TRACK/SS
GND
V
FB
BG
GND
38221 TA01
Efficiency/Power Loss vs Load Current
100
V
IN
3.3V
EFFICIENCY (%)
90
80
70
60
50
40
30
20
10
0
10
V
IN
= 3.3V
V
OUT
= 1.8V
FIGURE 10 CIRCUIT
100
1000
LOAD CURRENT (mA)
Burst Mode
POWER LOSS
0.01
0.1
Burst Mode
EFFICIENCY
10
V
IN
47µF
×2
0.47µH
1
POWER LOSS (W)
0.1µF
V
OUT
1.8V
47µF 8A
×2
0.001
10000
38221f
59k
118k
38221 TA01b
1
LTC3822-1
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Input Supply Voltage (V
IN
) ........................ –0.3V to 4.5V
BOOST Voltage .......................................... –0.3V to 10V
PLLLPF, RUN, IPRG, SYNC/MODE,
TRACK/SS Voltages .......................–0.3V to (V
IN
+ 0.3V)
V
FB
, I
TH
Voltages ....................................... –0.3V to 2.4V
SW Voltage ............................................ –2V to V
IN
+ 1V
Operating Temperature Range (Note 2) ... –40°C to 85°C
Storage Ambient Temperature Range
DD ..................................................... –65°C to 125°C
GN ..................................................... –65°C to 150°C
Junction Temperature (Note 3) ............................. 125°C
Lead Temperature (Soldering, 10 sec)
GN Only ............................................................ 300°C
PACKAGE/ORDER INFORMATION
TOP VIEW
TOP VIEW
PLLLPF
SYNC/MODE
TRACK/SS
V
FB
I
TH
RUN
1
2
3
4
5
6
13
12 SW
11 V
IN
10 BOOST
9 TG
8 BG
7 IPRG
GND
PLLLPF
SYNC/MODE
PGOOD
TRACK/SS
V
FB
I
TH
RUN
1
2
3
4
5
6
7
8
16 SW
15 SENSE
–
14 V
IN
13 BOOST
12 TG
11 BG
10 IPRG
9
GND
DD PACKAGE
12-LEAD (3mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB
GN PACKAGE
16-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 110°C/W
ORDER PART NUMBER
LTC3822EDD-1
DD PART MARKING
LCMS
ORDER PART NUMBER
LTC3822EGN-1
GN PART MARKING
38221
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
PARAMETER
Main Control Loops
V
IN
Input DC Supply Current
Normal Operation
Sleep Mode
Shutdown
UVLO
Undervoltage Lockout Threshold
Shutdown Threshold Of RUN Pin
Regulated Feedback Voltage
Output Voltage Line Regulation
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
Operating Voltage Range
(Note 4)
RUN = 0
V
IN
= UVLO Threshold – 200mV
V
IN
Falling
V
IN
Rising
(Note 5)
2.75V < V
IN
< 4.5V (Note 5)
●
●
●
MIN
2.75
TYP
3.3
360
105
7.5
10
MAX
4.5
525
150
20
20
2.55
2.75
1.4
0.606
0.1
UNITS
V
µA
µA
µA
V
V
V
V
%/V
38221f
1.95
2.15
0.7
0.594
2.25
2.45
1.1
0.6
0.025
2
LTC3822-1
ELECTRICAL CHARACTERISTICS
PARAMETER
Output Voltage Load Regulation
TRACK/SS Pull-Up Current
V
FB
Input Current
Overvoltage Protect Threshold
Overvoltage Protect Hysteresis
Top Gate (TG) Drive Rise Time
Top Gate (TG) Drive Fall Time
Bottom Gate (BG) Drive Rise Time
Bottom Gate (BG) Drive Fall Time
Maximum Duty Cycle
Maximum Current Sense Voltage (V
IN
– SW)
(ΔV
SENSE(MAX)
)
Soft-Start Time
Oscillator
Oscillator Frequency
PLLLPF = Floating
PLLLPF = 0V
PLLLPF = V
IN
SYNC/MODE Clocked
Minimum Synchronizable Frequency
Maximum Synchronizable Frequency
f
OSC
> f
SYNC/MODE
f
OSC
< f
SYNC/MODE
I
PGOOD
Sinking 1mA
V
FB
with Respect to Set Output Voltage
V
FB
< 0.6V, Ramping Postive
V
FB
< 0.6V, Ramping Negative
V
FB
> 0.6V, Ramping Negative
V
FB
> 0.6V, Ramping Positive
–13
–16
7
10
480
240
640
550
300
750
200
1000
–5
5
100
–10.0
–13.3
10.0
13.3
–7
–10
13
16
600
340
850
250
kHz
kHz
kHz
kHz
kHz
µA
µA
mV
%
%
%
%
C
L
= 3000pF
C
L
= 3000pF
C
L
= 3000pF
C
L
= 3000pF
In Dropout
IPRG = Floating
IPRG = 0V
IPRG = V
IN
Time for V
FB
to Ramp from 0.05V to 0.55V
●
●
●
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
I
TH
= 1.3V to 0.9V (Note 5)
I
TH
= 1.3V to 1.7V
TRACK/SS = 0V
(Note 5)
Measured at V
FB
0.66
0.65
MIN
TYP
0.1
–0.1
1
10
0.68
20
40
40
50
40
99
110
70
185
125
82
200
650
140
95
220
MAX
0.5
–0.5
1.35
50
0.70
UNITS
%
%
µA
nA
V
mV
ns
ns
ns
ns
%
mV
mV
mV
µs
Phase-Locked Loop Lock Range
750
Phase detector Output Current
Sinking
Sourcing
PGOOD Output (GN Package Only)
PGOOD Voltage Low
PGOOD Trip Level
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 LTC3822E-1 is guaranteed to meet specified performance
from 0°C to 85°C. Specifications over the –40°C to 85°C operating range
are assured by design characterization, and correlation with statistical
process controls.
Note 3:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
T
J
= T
A
+ (P
D
•
θ
JA
)
Note 4:
Dynamic supply current is higher due to gate charge being
delivered at the switching frequency.
Note 5:
The LTC3822-1 is tested in a feedback loop that servos I
TH
to a
specified voltage and measures the resultant V
FB
voltage.
38221f
3
LTC3822-1
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency/Power Loss
vs Load Current
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
10
POWER LOSS
0.1
V
IN
= 3.3V, V
OUT
= 1.8V
100
V
OUT
AC COUPLED
200mV/DIV
POWER LOSS (W)
V
OUT
AC COUPLED
200mV/DIV
T
A
= 25°C unless otherwise noted.
Load Step (Continuous Mode)
Load Step (Pulse Skip Mode)
10
EFFICIENCY
1
INDUCTOR
CURRENT
2A/DIV
38221 G02
INDUCTOR
CURRENT
2A/DIV
38221 G04
FIGURE 10 CIRCUIT
0.01
Burst Mode OPERATION
PULSE SKIPPING
CONTINUOUS MODE
0.001
100
1000
10000
LOAD CURRENT (mA)
38221 G01
50µs/DIV
FIGURE 10 CIRCUIT
50µs/DIV
FIGURE 10 CIRCUIT
Load Step (Burst Mode Operation)
0.604
V
OUT
AC COUPLED
200mV/DIV
0.603
FEEDBACK VOLTAGE (V)
Regulated Feedback Voltage
vs Temperature
2.55
2.50
INPUT VOLTAGE (V)
2.45
2.40
2.35
2.30
Undervoltage Lockout Threshold
vs Temperature
V
IN
RISING
0.602
0.601
0.600
0.599
0.598
0.597
0.596
–50
0
50
TEMPERATURE (°C)
100
38212 G06
INDUCTOR
CURRENT
2A/DIV
38221 G05
V
IN
FALLING
2.25
2.20
2.15
–60 –40 –20 0
20 40 60
TEMPERATURE (°C)
80
100
50µs/DIV
FIGURE 10 CIRCUIT
38221 G07
Shutdown (RUN) Threshold
vs Temperature
MAXIMUM CURRENT SENSE THRESHOLD (mV)
1.20
135
Maximum Current Sense
Threshold vs Temperature
IPRG = FLOAT
NORMALIZED FREQUENCY SHIFT (%)
10
8
6
4
2
0
–2
–4
–6
–8
Oscillator Frequency
vs Temperature
1.15
RUN VOLTAGE (V)
130
1.10
125
1.05
120
1.00
–60 –40 –20 0
20 40 60
TEMPERATURE (°C)
80
100
115
–60 –40 –20 0
20 40 60
TEMPERATURE (°C)
80
100
–10
–60 –40 –20 0
20 40 60
TEMPERATURE (°C)
80
100
38221 G08
3822 G09
38221 G10
38221f
4
LTC3822-1
TYPICAL PERFORMANCE CHARACTERISTICS
Oscillator Frequency
vs Input Voltage
5
NORMALIZED FREQUENCY SHIFT (%)
4
3
2
1
0
–1
–2
–3
–4
–5
2.5
–20
3.0
3.5
4.0
INPUT VOLTAGE (V)
4.5
38221 G11
T
A
= 25°C unless otherwise noted.
Shutdown Quiescent Current
vs Input Voltage
18
16
SHUTDOWN CURRENT (µA)
2
38221 G03
Maximum Current Sense Voltage
vs I
TH
Pin Voltage
100
80
CURRENT LIMIT (%)
60
40
20
0
Burst Mode OPERATION
(I
TH
RISING)
Burst Mode OPERATION
(I
TH
FALLING)
FORCED CONTINUOUS
MODE
PULSE SKIPPING
MODE
14
12
10
8
6
4
2
0.5
1
1.5
I
TH
VOLTAGE (V)
0
2.5
3.0
3.5
4.0
INPUT VOLTAGE (V)
4.5
38221 G12
Quiescent Current in Normal
Operation vs Input Voltage
390
380
QUIESCENT CURRENT (µA)
Start-Up with Internal Soft-Start
V
RUN
1V/DIV
V
TRACK/SS
1V/DIV
Start-Up with External Soft-Start
Capacitor
V
RUN
1V/DIV
370
360
350
340
330
2.5
200µs/DIV
FIGURE 10 CIRCUIT
V
IN
= 3.3V
V
OUT
= 1.8V
R
LOAD
= 1.5Ω
38221 G14
V
OUT
1V/DIV
V
OUT
1V/DIV
3.0
3.5
4.0
INPUT VOLTAGE (V)
4.5
3822 G13
4ms/DIV
FIGURE 10 CIRCUIT
V
IN
= 3.3V
V
OUT
= 1.8V
R
LOAD
= 1.5Ω
C
SS
= 0.01µF
38221 G15
Soft-Start with Tracking
Continuous Mode Operation
V
TRACK/SS
500mV/DIV
V
SW
2V/DIV
V
OUT
20mV/DIV
AC COUPLED
I
L
2A/DIV
4ms/DIV
FIGURE 10 CIRCUIT
V
IN
= 3.3V
V
OUT
= 1.8V
R
LOAD
= 1.5Ω
38221 G16
V
OUT
1V/DIV
2µs/DIV
FIGURE 10 CIRCUIT
V
IN
= 3.3V
V
OUT
= 1.8V, 100mA
38221 G17
38221f
5
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