LT1610 Linear Technology, LT1610 Datasheet - Page 10

• Manufacturer Part Number: LT1610
• Description: Constant-Current/ Constant-Voltage 1.4MHz Step-Up DC/DC Converter
• Manufacturer: Linear Technology

APPLICATIONS
LT1610
output capacitor because it introduces a zero in the
regulator’s loop gain. This zero may not be effective
because the ceramic capacitor’s ESR is very low. Most
current mode switching regulators (including the LT1610)
can easily be compensated without this zero. Any design
should be tested for stability at the extremes of operating
temperatures; this is particularly so of circuits that use
ceramic output capacitors.
Figure 9 details a 2.5V to 5V boost converter. Transient
response to a 5mA to 105mA load step is pictured in Figure
10. The “double trace” of V
ESR of C2. This ESR aids stability. In Figure 11, C2 is
replaced by a 10 F ceramic capacitor. Note the low phase
margin; at higher input voltage, the converter may oscil-
late. After replacing the internal compensation network
with an external 220pF/220k series RC, the transient
response is shown in Figure 12. This is acceptable tran-
sient response.
Table 1
10
2.5V
FIGURE
V
IN
Figure 9. 2.5V to 5V Boost Converter Can Operate with a
Ceramic Output Capacitor as Long as Proper R
are Used. Disconnect COMP Pin if External Compensation
Components Are Used
10
11
12
C1: AVX TAJA226M006
C2: SEE TABLE
D1: MOTOROLA MBR0520
L1: MURATA LQH30100
+
C1
22 F
AVX TAJA226M006 Tantalum
Taiyo Yuden JMK316BJ106
Taiyo Yuden JMK316BJ106
C2
R
C
C
C
3
1
U
SHDN
V
COMP
C
V
IN
8
6
LT1610
10 H
INFORMATION
L1
U
OUT
PGND
SW
at 105mA load is due to the
GND
4
5
FB
2
D1
7
W
1M
R2
324k
COMPENSATION
220pF/220k
C
Internal
Internal
+
and C
U
C2
22 F
C
1610 F09
V
5V
100mA
OUT
100mV/DIV
100mV/DIV
100mV/DIV
CURRENT
CURRENT
CURRENT
Figure 12. Ceramic Output Capacitor with 220pF/220k
External Compensation has Adequate Phase Margin
Figure 11. 10 F X5R-Type Ceramic Output Capacitor
and Internal RC Compensation has Low Phase Margin
105mA
105mA
105mA
LOAD
LOAD
LOAD
V
5mA
V
V
5mA
5mA
OUT
OUT
OUT
Figure 10. Tantalum Output Capacitor
and Internal RC Compensation
500 s/DIV
500 s/DIV
500 s/DIV
1610 F10
1610 F11
1610 F12