Datasheet
LTC3421
5
3421f
Burst Mode Threshold vs R
BURST
FB Voltage Frequency Accuracy
Burst Mode Quiescent Current Current Limit Accuracy R
DS(ON)
R
BURST
(kΩ)
20
0
OUTPUT CURRENT (mA)
20
60
80
100
INTO BURST
OUT OF BURST
120
180
3421 G10
40
70
120
140
160
TEMPERATURE (°C)
–45
1.20
VOLTAGE (V)
1.21
1.22
1.23
1.24
–30 –15 0 15
3421 G11
30 45 60 75 90
TEMPERATURE (°C)
–45
0.95
FREQUENCY (MHz)
0.97
0.99
1.01
1.03
–30 –15 0 15
3421 G12
30 45 60 75 90
TEMPERATURE (°C)
–45
0
CURRENT (µA)
5
10
15
20
–30 –15 0 15
3421 G13
30 45 60 75 90
FB (Pin 1): Feedback Pin. Connect resistor divider tap
here. The output voltage can be adjusted from 2.4V to
5.25V. The feedback reference voltage is typically 1.220V.
SHDN (Pin 2): Shutdown Pin. Less than 0.25V on this pin
shuts down the IC. The IC is enabled when the SHDN
voltage is greater than 1V. Once V
OUT
is above 2.2V,
hysteresis is applied to the pin (–500nA out of the pin)
allowing it to operate at a logic high while the battery can
drop to 0.5V.
V
REF
(Pin 3): Buffered 1.22V Reference Output. This pin
can source up to 100µA and sink up to 8µA. This pin must
be decoupled with a 0.1µF capacitor for stability.
PI FU CTIO S
UUU
ENB (Pin 4): Reference Output (V
REF
) and Low-Battery
Comparator Enable. When ENB = Low, the V
REF
output and
low-battery comparator are disabled, which lowers the
quiescent current by 5µA. When ENB = High, the V
REF
output and the low-battery comparator are enabled. Dur-
ing shutdown, if the ENB = High and the output voltage is
pulled up to greater than 2.5V from a secondary source
such as a coin cell through a Schottky diode, the V
REF
output and low-battery comparator becomes powered
from the output voltage and enabled.
TEMPERATURE (°C)
–45
1.20
CURRENT (A)
1.25
1.35
1.40
1.45
1.70
1.55
–15
15
30 90
3421 G14
1.30
1.60
1.65
1.50
–30 0
45
60
75
R
LIM
= 105k
TEMPERATURE (°C)
–45
0
RESISTANCE (Ω)
0.02
0.06
0.08
0.10
0.20
0.14
–15
15
30 90
3421 G15
0.04
0.16
0.18
0.12
–30 0
45
60
75
PMOS
NMOS
TYPICAL PERFOR A CE CHARACTERISTICS
UW
(T
A
= 25°C, unless otherwise specified)