LT1611 Linear Technology, LT1611 Datasheet - Page 11

• Manufacturer Part Number: LT1611
• Description: Constant-Current/ Constant-Voltage 1.4MHz Step-Up DC/DC Converter
• Manufacturer: Linear Technology

OPERATIO
Capacitors
As described previously, ceramic capacitors can be used
with the LT1611 provided loop stability is considered. For
lower cost applications, small tantalum units can be used.
A value of 22 F is acceptable, although larger capacitance
values can be used. ESR is the most important parameter
in selecting an output capacitor. The “flying” capacitor (C2
in the schematic figures) should be a 1 F ceramic type. An
X5R or X7R dielectric should be used to avoid capacitance
decreasing severely with applied voltage. The input by-
pass capacitor is less critical, and either tantalum or
TYPICAL APPLICATIO S
Table 1. Inductor Vendors
VENDOR
Sumida
Murata
Coiltronics
Table 2. Capacitor Vendors
VENDOR
Taiyo Yuden
AVX
Murata
U
PHONE
[phone]
[phone]
[phone]
PHONE
[phone]
[phone]
[phone]
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
U
3.3V
“Charge Pump” Inverting DC/DC Converter
C1, C2: TAIYO YUDEN LMK212BJ105MG
C3: TAIYO YUDEN JMK325BJ226MM
D1, D2: MBR0520
L1: MURATA LQH3C-100
C1
1 F
URL
www.sumida.com
www.murata.com
www.coiltronics.com
URL
www.t-yuden.com
www.avxcorp.com
www.murata.com
V
SHDN
IN
LT1611
10 H
GND
L1
NFB
SW
ceramic can be used with little trade-off in circuit perfor-
mance. Some capacitor types appropriate for use with the
LT1611 are listed in Table 2.
Diodes
A Schottky diode is recommended for use with the LT1611.
The Motorola MBR0520 is a very good choice. Where the
input to output voltage differential exceeds 20V, use the
MBR0530 ( a 30V diode). If cost is more important than
efficiency, a 1N4148 can be used, but only at low current
loads.
1 F
C2
29.4k
10k
PART
CLS62-22022
CD43-470
LQH3C-220
CTX20-1
PART
Ceramic Caps
Ceramic Caps
Tantalum Caps
Ceramic Caps
D1
C3
22 F
1611 TA02
–5V
70mA
D2
COMMENT
22 H Coupled
47 H
22 H, 2mm Height
20 H Coupled, Low DCR
COMMENT
X5R Dielectric
LT1611
11