LTC1735
ELECTRICAL CHARACTERISTICS
Note 3:
The LTC1735 is tested in a feedback loop that servos V
OSENSE
to
the balance point for the error amplifier (V
ITH
= 1.2V).
Note 4:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 5:
Oscillator frequency is tested by measuring the C
OSC
charge
current (I
OSC
) and applying the formula:
Note 6:
The minimum on-time condition corresponds to an inductor peak-
to-peak ripple current
≥40%
of I
MAX
(see Minimum On-Time
Considerations in the Applications Information section).
Note 7:
Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels.
Note 8:
The LTC1735E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. The LTC1735I specifications are
guaranteed over the full –40°C to 85°C operating temperature range.
f
OSC
–1
8.477(10
11
)
1
1
=
+
C
OSC
(pF )
+
11
I
CHG
I
DIS
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency vs Load Current
(3 Operating Modes)
100
90
80
EFFICIENCY (%)
EXTV
CC
OPEN
BURST
EFFICIENCY (%)
70
CONTINUOUS
60
50
40
30
20
0.001
V
IN
= 10V
V
OUT
= 3.3V
R
S
= 0.01Ω
f
O
= 300kHz
0.1
0.01
1
LOAD CURRENT (A)
10
1735 G01
EFFICIENCY (%)
SYNC
Efficiency vs Input Voltage
100
0
EXTV
CC
OPEN
V
OUT
= 1.6V
95 FIGURE 1
90
I
OUT
= 5A
85
I
OUT
= 0.5A
80
75
NORMALIZED V
OUT
(%)
–0.1
EFFICIENCY (%)
V
IN
– V
OUT
(mV)
70
0
5
10
15
20
INPUT VOLTAGE (V)
4
U W
25
1735 G04
Efficiency vs Load Current
100
90
80
V
IN
= 24V
70
60
50
40
0.01
EXTV
CC
= 5V
FIGURE 1
V
IN
= 5V
100
V
IN
= 15V
95
90
Efficiency vs Input Voltage
EXTV
CC
= 5V
V
OUT
= 1.6V
FIGURE 1
I
OUT
= 5A
85
I
OUT
= 0.5A
80
75
70
0.1
1
LOAD CURRENT (A)
10
1735 G02
0
5
10
15
20
INPUT VOLTAGE (V)
25
30
1735 G03
Load Regulation
500
FCB = 0V
V
IN
= 15V
FIGURE 1
V
IN
– V
OUT
Dropout Voltage
vs Load Current
R
SENSE
= 0.005Ω
V
OUT
= 5V – 5% DROP
400
300
–0.2
200
–0.3
100
–0.4
0
0
2
6
4
LOAD CURRENT (A)
8
10
1735 G05
30
0
2
4
6
LOAD CURRENT (A)
8
10
1735 G06
1735fc
LINER [ LINEAR TECHNOLOGY ]
