LT1307CS8 Linear Technology, LT1307CS8 Datasheet - Page 15

• Manufacturer Part Number: LT1307CS8
• Description: IC DC/DC CONV SINGLE CELL 8-SOIC
• Manufacturer: Linear Technology
• Type: Step-Up (Boost)r

Specifications of LT1307CS8

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 3.3V, 5V
• Current - Output: 100mA
• Frequency - Switching: 600kHz
• Voltage - Input: 1 ~ 5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

This circuit overcomes the limitation of load-based
transitioning between Burst Mode operation and constant
switching mode by adding external control. If M1’s gate is
grounded by an external open-drain signal, the converter
functions normally in constant switching mode, delivering
3.3V. Output noise is low, however efficiency at loads less
than 1mA is poor due to the 1mA supply current of the
LT1307B. If M1’s gate is allowed to float, the low-battery
TYPICAL APPLICATIO S
This photo details output voltage as the circuit is switched
between the two modes. Load current is 100 A in Burst
Mode operation; 10mA in constant switching mode.
500mV/DIV
I
L
100 A
10mA
V
OUT
GROUND = HIGH POWER/LOW NOISE
FLOAT = Burst Mode OPERATION
2
CELLS
1 F
CERAMIC
100k
2N7002
1nF
0.2s/DIV
M1
U
V
OUT
Externally Controlled Burst Mode Operation
300k
SHDN
V
LBO
V
1307 F20
C
IN
LT1307B
SHUTDOWN
10 H
10M
R1
L1
GND
SW
LBI
FB
detector now drives the V
to 3V by allowing M1’s gate to go to V
voltage drops below 3V. R1 adds hysteresis, resulting in
low-frequency Burst Mode operation ripple voltage at the
output. By pulling the V
current of the LT1307B drops to 60 A, resulting in accept-
able efficiency at loads in the 100 A range.
This photo shows transient response in constant switch-
ing mode with a 10mA to 100mA stepped load. Output
ripple at the switching frequency can be reduced consid-
erably by adding a 10 F ceramic capacitor in parallel with
the 100 F tantalum.
MBR0520
100mV/DIV
R5
590k
I
L
100mA
10mA
V
OUT
R2
49.9k
698k
R3
1M
R4
C2*
10 F
CERAMIC
+
C
C
2ms/DIV
1307 F19
pin. R3 and R2 set the output
V
3.3V
200mA
C1
100 F
pin below a V
LT1307/LT1307B
OUT
*
3.0V IN LOW-POWER
Burst Mode OPERATION
C1 = AVX TPSC107K006R0150
L1 = COILCRAFT DO1608-103
C2 OPTIONAL: REDUCES OUTPUT
RIPPLE CAUSED BY C1'S ESR
OUT
SUMIDA CD43-100
until the output
BE
1307 F21
, quiescent
15
1307fa