LT1930ES5 Linear Technology, LT1930ES5 Datasheet - Page 4

• Manufacturer Part Number: LT1930ES5
• Manufacturer: Linear Technology

Specifications of LT1930ES5

• Dc To Dc Converter Type: Step Up
• Number Of Outputs: 1
• Pin Count: 5
• Input Voltage: 16V
• Output Voltage: 1.255 to 34V
• Switching Freq: 1400KHz
• Output Current: 2A
• Package Type: TSOT-23
• Output Type: Adjustable
• Switching Regulator: Yes
• Line Regulation: 0.05%/V
• Mounting: Surface Mount
• Input Voltage (min): 2.45V
• Operating Temperature Classification: Industrial
• Lead Free Status / Rohs Status: Not Compliant

BLOCK DIAGRA
LT1930/LT1930A
OPERATIO
The LT1930 uses a constant frequency, current-mode
control scheme to provide excellent line and load regula-
tion. Operation can be best understood by referring to the
block diagram in Figure 2. At the start of each oscillator
cycle, the SR latch is set, which turns on the power switch
Q1. A voltage proportional to the switch current is added
to a stabilizing ramp and the resulting sum is fed into the
positive terminal of the PWM comparator A2. When this
voltage exceeds the level at the negative input of A2, the SR
latch is reset turning off the power switch. The level at the
negative input of A2 is set by the error amplifier A1, and is
simply an amplified version of the difference between the
feedback voltage and the reference voltage of 1.255V. In
4
SHUTDOWN
V
U
IN
V
4
5
OUT
R1 (EXTERNAL)
R2 (EXTERNAL)
SHDN
W
FB
REFERENCE
1.255V
3
FB
–
+
A1
Figure 2. Block Diagram
R
C
C
C
this manner, the error amplifier sets the correct peak
current level to keep the output in regulation. If the error
amplifier’s output increases, more current is delivered to
the output; if it decreases, less current is delivered. The
LT1930 has a current limit circuit not shown in Figure 2.
The switch current is constantly monitored and not al-
lowed to exceed the maximum switch current (typically
1.2A). If the switch current reaches this value, the SR latch
is reset regardless of the state of comparator A2. This
current limit helps protect the power switch as well as the
external components connected to the LT1930.
The block diagram for the LT1930A (not shown) is iden-
tical except that the oscillator frequency is 2.2MHz.
OSCILLATOR*
GENERATOR
1.2MHz
RAMP
–
+
*2.2MHz FOR LT1930A
COMPARATOR
A2
R
S
Q
DRIVER
+
–
1
2
Q1
0.01
1930/A BD
SW
GND