LTC3822-1 Datasheet, PDF (1/24 Pages) Linear Technology – No RSENSE, Low Input Voltage, Synchronous Step-Down DC/DC Controller

LTC3822-1
FEATURES
No R_SENSE^TM, Low Input
Voltage, Synchronous
Step-Down DC/DC Controller
DESCRIPTION
■ _{Dual N-Channel MOSFET Synchronous Drive}
■ _{No Current Sense Resistor Required}
■ _{Optimized for 3.3VIN 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: IQ = 7.5µA}
■ _{Tiny Thermally Enhanced 12-Pin (3mm × 3mm) DFN}
or 16-Pin Narrow SSOP Packages
APPLICATIONS
■ _{Single Cell Li-Ion Powered Systems}
■ _{3.3VIN 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.
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
Operation
Continuous, Discontinuous Discontinuous Mode
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
TYPICAL APPLICATION
10.2k
1nF
IPRG
V_IN
RUN
PLLLPF TG
LTC3822-1
I_TH
SW
BOOST
SYNC/MODE
TRACK/SS
GND
BG
V_FB
GND
59k 118k
0.47µH
0.1µF
V_IN
47µF
3.3V
×2
47µF
×2
V_OUT
1.8V
8A
38221 TA01
Efficiency/Power Loss vs Load Current
100
10
90
Burst Mode
80
EFFICIENCY
1
70
60
50
40
30
20
10
0
10
0.1
Burst Mode
POWER LOSS
0.01
V_IN = 3.3V
V_OUT = 1.8V
FIGURE 10 CIRCUIT _0.001
100
1000
10000
LOAD CURRENT (mA) 38221 TA01b
38221f
1