LT1611 Datasheet, PDF (1/12 Pages) Linear Technology – Inverting 1.4MHz Switching Regulator in SOT-23

LT1611
Inverting 1.4MHz Switching
Regulator in SOT-23
FEATURES
s _{Very Low Noise: 1mVP–P Output Ripple}
s _{– 5V at 150mA from a 5V Input}
s _{Better Regulation Than a Charge Pump}
s _{Effective Output Impedance: 0.14Ω}
s _{Uses Tiny Capacitors and Inductors}
s _{Internally Compensated}
s _{Fixed Frequency 1.4MHz Operation}
s _{Low Shutdown Current: <1µA}
s _{Low VCESAT Switch: 300mV at 300mA}
s _{Tiny 5-Lead SOT-23 Package}
U
APPLICATIO S
s _{MR Head Bias}
s _{Digital Camera CCD Bias}
s _{LCD Bias}
s _{GaAs FET Bias}
s _{Positive-to-Negative Conversion}
DESCRIPTIO
The LT^®1611 is the industry’s first inverting 5-lead SOT-23
current mode DC/DC converter. Intended for use in small,
low power applications, it operates from an input voltage
as low as 1.1V and switches at 1.4MHz, allowing the use
of tiny, low cost capacitors and inductors 2mm or less in
height. Its small size and high switching frequency enable
the complete DC/DC converter function to consume less
than 0.25 square inches of PC board area. Capable of
generating – 5V at 150mA from a 5V supply or – 5V at
100mA from a 3V supply, the LT1611 replaces nonregulated
“charge pump” solutions in many applications.
The LT1611 operates in a dual inductor inverting topology
which filters the input side as well as the output side of the
DC/DC converter. Fixed frequency switching ensures a
clean output free from low frequency noise typically present
with charge pump solutions. No load quiescent current of
the LT1611 is 3mA, while in shutdown quiescent current
drops to 0.5µA. The 36V switch allows V_IN to V_OUT
differential of up to 33V.
The LT1611 is available in the 5-lead SOT-23 package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
L1A
V_IN
22µH
5V
V_IN
SW
+
C1
SHDN
LT1611
22µF
NFB
GND
C2
1µF
L1B
22µH
R1
29.4k
R2
10k
D1
1200pF
C1: AVX TAJB226M010
C2: TAIYO YUDEN LMK212BJ105MG
C3: TAIYO YUDEN JMK325BJ226MM (1210 SIZE)
D1: MBR0520
L1: SUMIDA CLS62-220 OR 2× MURATA LQH3C220 (UNCOUPLED)
V_OUT
–5V
150mA
C3
22µF
V_OUT
20mV/DIV
AC COUPLED
150mA
LOAD CURRENT
50mA
1611 TA01
Figure 1. 5V to – 5V, 150mA Low Noise Inverting DC/DC Converter
Transient Response
100µs/DIV
1611 F10
1