LTC3421_15 Datasheet, PDF (1/16 Pages) Linear Technology – 3A, 3MHz Micropower Synchronous Boost Converter with Output Disconnect

LTC3421
3A, 3MHz Micropower
Synchronous Boost Converter
with Output Disconnect
FEATURES
s _{Synchronous Rectification: Up to 96% Efficiency}
s _{True Output Disconnect}
s _{Inrush Current Limiting}
s _{Very Low Quiescent Current: 12µA}
s _{Up to 1.5A Continuous Output Current}
s _{Fixed Frequency Operation Up to 3MHz}
s _{0.5V to 4.5V Input Range}
s _{2.4V to 5.25V Adjustable Output Voltage}
s _{Guaranteed 1V Start-Up}
s _{Programmable Current Limit}
s _{Programmable Soft-Start}
s _{Synchronizable Oscillator}
s _{Manual or Automatic Burst Mode}^® _Operation
s _{Low-Battery Comparator}
s _{< 1µA Shutdown Current}
s _{1.22V Reference Output Voltage}
s _{Small (4mm × 4mm) Thermally Enhanced QFN}
Package
U
APPLICATIO S
s _{Handheld Computers}
s _{Cordless Phones}
s _{GPS Receivers}
s _{Battery Backup Supplies}
DESCRIPTIO
The LTC^®3421 is a high efficiency, current mode, fixed
frequency, step-up DC/DC converter with true output dis-
connect and inrush current limiting. The device includes a
0.10Ω N-channel MOSFET switch and a 0.14Ω P-channel
synchronous rectifier. This product has the ability to sim-
ply program the output voltage, switching frequency, cur-
rent limit, soft-start, Burst Mode threshold and loop
compensation with external passive components.
Quiescent current is only 12µA during Burst Mode opera-
tion, maximizing battery life in portable applications. The
oscillator frequency can be programmed up to 3MHz and
can be synchronized to an external clock applied to the
SYNC pin. An open-drain uncommitted low-battery com-
parator is included. The part maintains operation in
applications with a secondary cell powering the output
voltage during shutdown.
Other features include: 1µA shutdown, antiringing control,
thermal limit and reference output.
The LTC3421 is available in a small 4mm × 4mm QFN
package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
V_IN
1.8V TO 3V
L1
4.7µH
2
CELLS
C1*
4.7µF
2
SHDN
4
ENB
3 _VREF
23
LBI
22
LBO
7
SYNC
8
I_LIM
45.3k
SS R_T
21 14 15 16
V_IN SW SW SW
18
V_OUTS
17
V_OUT
V_OUT ¹⁹
LTC3421
20
V_OUT
1
FB
V_C ²⁴
BURST ⁹
GND PGND PGND PGND
65
10 11 12 13
0.1µF
28k
0.1µF
340k
V_OUT
3.3V
1.2A
470pF
C5*
22µF
200k
20k
100k
*LOCATE COMPONENTS CLOSE TO PINS
C1: TAIYO YUDEN JMK212BJ106MM
C5: TAIYO YUDEN JMK325BJ226MM
L1: TDK RLF7030T-4R7M3R4
3421 TA01
2-Cell to 3.3V Efficiency
100
Burst Mode OPERATION
90
V_IN = 3V
80
70
60
50
V_IN = 2.4V
V_IN = 2V
40
30
20
10 ^VOUT ^{= 3.3V}
f_OSC = 1MHz
0
0.1
1
10
100
OUTPUT CURRENT (mA)
1000
3421 G02
3421f
1