LTC3537
1
3537fd
TYPICAL APPLICATION
FEATURES
APPLICATIONS
DESCRIPTION
2.2 MHz, 600mA
Synchronous Step-Up DC/DC
Converter and 100mA LDO
The LTC
?/DIV>
3537 combines a high ef ciency, 2.2MHz step-up
DC/DC converter with an independent 100mA low dropout
regulator (LDO). The step-up converter starts from an input
voltage as low as 0.68V and contains an internal 0.4?
switch and a 0.6?synchronous recti er that disconnects
from the output when disabled in shutdown.
A switching frequency of 2.2MHz minimizes solution
footprint by allowing the use of tiny, low pro le inductors
and ceramic capacitors. The current mode PWM design
is internally compensated, reducing external parts count.
Fixed frequency switching is maintained until a light load
current is sensed, at which point Burst Mode
?/DIV>
operation is
engaged to maximize ef ciency. For low noise operation,
Burst Mode Operation can be disabled. Anti-ring circuitry
reduces EMI by damping the inductor in discontinuous
mode. Additional features include a low shutdown current
of under 1糀 and thermal overload protection.
The integrated LDO regulator provides a very low noise,
programmable low dropout supply.
n
High Ef ciency Step-Up DC/DC Converter and LDO
Step-Up
n
V
IN
: 0.68V to 5V, V
OUT
: 1.5V to 5.25V
I
OUT
: 100mA at 3.3V, V
IN
>0.8V
n
2.2MHz Fixed Frequency Operation
n
Synchronous Recti er with Output Disconnect
n
Burst Mode Operation (Pin Selectable)
Linear LDO Regulator
n
V
IN
: 1.8V to 5.5V, V
OUT
: 0.6V to 5V
I
OUT
: 100mA
n
100mV Dropout Voltage at 50mA
n
24dB Ripple Rejection at f
SW
Combined
n
Power Good Indicators
n
Low-Battery Comparator
n
30?/SPAN>A I
Q
n
Low Pro le 3mm ?/SPAN> 3mm ?/SPAN> 0.75mm Package
n
Wireless Microphones
n
Portable Medical instruments
n
Noise Cancelling/Portable Headsets
n
RF and Audio Power
L, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Ef ciency and Power Loss
vs Load Current
LOAD CURRENT (mA)
0.01
100
80
90
60
20
30
40
70
50
10
0
1000
10
0.1
1
100
0.01
10
0.1
3537 TA01b
1000
1
100
EFFICIENCY
POWER LOSS
V
INB
, MODE = 1.8V
3537 TA01a
LTC3537
V
INB
1糉
ALKALINE
0.8V
TO
1.6V
V
OUTB
3.3V
V
OLDO
3V
2.2糎
R6
665k
ENLDO
V
OUTB
FBB
V
INL
V
OLDO
FBL
ENBST
MODE
PGND
SGND
SW
R2
1.74M
R1
1M
R3
511k
R4
2.05M
R5
1.0M
10糉
1糉
ON
OFF
BURST
PWM
PGDL
PGDB
LBO
LBI
+
33pF