LT1611 Linear Technology, LT1611 Datasheet - Page 6

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

OPERATIO
LT1611
Transient Response
The inverting architecture of the LT1611 can generate a
very low ripple output voltage. Recently available high
value ceramic capacitors can be used successfully in
LT1611 designs with the addition of a phase lead capaci-
tor, C
resistor R1, this capacitor reduces both output perturba-
6
PL
(see Figure 7). Connected in parallel with feedback
V
V
IN
IN
+
+
U
Figure 6. Switch-Off Phase of Inverting Converter. L1 and L2 Current Have Negative dI/dt
C1
Figure 5. Switch-On Phase of Inverting Converter. L1 and L2 Current Have Positive dI/dt
C1
L1
L1
V
IN
+ V
V
CESAT
OUT
Q1
Q1
+ V
SW
SW
D
–(V
C2
C2
IN
+ V
V
D
SWX
OUT
SWX
)
D1
D1
tions due to load steps and output ripple voltage to very
low levels. To illustrate, Figure 7 shows an LT1611 invert-
ing converter with resistor loads R
connected across the output, while R
externally via a pulse generator. Output voltage wave-
forms are pictured in subsequent figures, illustrating the
performance of output capacitor type and the effect of C
connected across R1.
L2
L2
+
+
C3
C3
1611 F06
1611 F05
L1
R
R
LOAD
L2
LOAD
–V
and R
–V
OUT
OUT
is switched in
L2
. R
L1
PL
is