QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 433
ADJUSTABLE OUTPUT BOOST REGULATOR
LT1961
DESCRIPTION
Demonstration circuit 433 features a high frequency
1.25MHz 12Vout DC/DC monolithic boost converter fea-
turing the LT1961. This current-mode control monolithic
(switch included) converter has a wide operating supply
voltage, a minimum peak switch current rating of 1.5A,
and a low resistance 0.2Ω power switch. The switch cur-
rent limit is constant at all duty cycles. The tiny MSOP 8-
Pin exposed leadframe package is optimal for high
power in a tiny space with excellent heat dissipation ca-
pabilities.
The small size and wide input voltage of the LT1961 are
demonstrated by the 2.8V–12V input to 12V output
boost converter. The maximum output current varies
with respect to the input voltage. The board is optimized
for 5V input to 12V output at up to 450mA load current.
Table 1. Typical Performance Summary
PARAMETER
Input Voltage Range (V
IN
)
Output Voltage (V
OUT
)
Maximum Output Current
Maximum Output Current
Maximum Output Current
Maximum Output Current
Typical Switching Frequency
Typical Efficiency
V
IN
= 5V, V
OUT
= 12V, I
OUT
= 450mA
CONDITION
V
OUT
= 12V
2.8V
≤
V
IN
≤
12V
V
IN
= 3V, V
OUT
= 12V, ISW
PK
= 1.5A
V
IN
= 5V, V
OUT
= 12V, ISW
PK
= 1.5A
V
IN
= 8V, V
OUT
= 12V, ISW
PK
= 1.5A
V
IN
= 10V, V
OUT
= 12V, ISW
PK
= 1.5A
VALUE
2.8V–12V
12V ±3%
220mA
450mA
750mA
1A
1.25MHz
85%
Compensation components are designed for stable op-
eration over the entire input voltage range 2.8V–12V in-
put for this 12V output application. Adjustable feedback
resistors allow simple customization of the output volt-
age. For this particular output, stability and transient
response can be more optimally chosen for specific in-
put voltages such as 5V
IN
±10% or 3.3V
IN
±10%. The
high 1.25MHz switching frequency allows for the use of
tiny ceramic input and output capacitors as well as a
very small inductor, making possible tiny and low cost
boost converter solutions. High switching frequency re-
sults in lower output voltage ripple than lower frequency
converters.
Design files for this circuit board are available. Call
the LTC factory.
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 433
ADJUSTABLE OUTPUT BOOST REGULATOR
QUICK START PROCEDURE
Demonstration circuit 433 is easy to set up to evaluate
the performance of the LT1961. Refer to Figure 1 for
proper measurement equipment setup and follow the
procedure below:
Make sure that the input voltage does not exceed 12V.
The synchronization and shutdown functions are op-
tional and their pins can be left floating (disconnected) if
not being used.
–
+ +
+
–
–
1.
Connect the 2.8V–12V input power supply to the Vin
and Gnd terminals on the board.
2.
Since this demo circuit operates with low input volt-
ages and up to 1.1A output current, it is essential that
the input voltage source be well regulated. If the input
power supply is equipped with sense lines, connect
SENSE
+
to the Vin terminal and SENSE
–
to the Gnd
terminal on the board.
3.
Verify that the output voltage is 12V.
–
+
OPTIONAL
100
90
OPTIONAL
5V
IN
EFFICIENCY (%)
80
70
60
50
40
30
20
10
+
+
–
+
–
–
LOAD
0
0
100
200
300
400
500
600
LOAD CURRENT (mA)
Figure 1. Proper Measurement Equipment Setup
Figure 2. Efficiency vs. Load Current
2
京公网安备 11010802033920号
EEWORLD
