Datasheet

4
LT3437
3437fc
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LT3437EDD/LT3437EFE are guaranteed to meet performance
specifications from 0°C to 125°C junction temperature. Specifications over
the –40°C to 125°C operating junction temperature range are assured by
design, characterization and correlation with statistical process controls. The
LT3437IDD/LT3437IFE are guaranteed and tested over the full –40°C to
125°C operating junction temperature range. The LT3437HFE is also tested
to the LT3437 Electrical Characteristics table at 140°C operating junction
temperature. High junction temperatures degrade operating lifetimes.
Note 3: Minimum input voltage is defined as the voltage where switching
starts. Actual minimum input voltage to maintain a regulated output will
depend upon output voltage and load current. See Applications Information.
Note 4: Supply input current is the quiescent current drawn by the input
pin. Its typical value depends on the voltage on the BIAS pin and operating
state of the LT3437. With the BIAS pin at 0V, all of the quiescent current
required to operate the LT3437 will be provided by the V
IN
pin. With the
BIAS voltage above its minimum input voltage, a portion of the total
quiescent current will be supplied by the BIAS pin. Supply sleep current is
defined as the quiescent current during the “sleep” portion of Burst Mode
operation. See Applications Information for determining application supply
currents.
Note 5: Minimum BIAS voltage is the voltage on the BIAS pin when I
BIAS
is
sourced into the pin.
Note 6: This is the minimum voltage across the boost capacitor needed to
guarantee full saturation of the internal power switch.
Note 7: Boost current is the current flowing into the BOOST pin with the pin
held 3.3V above input voltage. It flows only during switch on time.
Note 8: Gain is measured with a V
C
swing from 1.15V to 750mV.
Note 9: Switch saturation voltage guaranteed by correlation to wafer level
measurements for DD package parts.
Note 10: The C
SS
threshold is defined as the value of current sourced into the
C
SS
pin which results in an increase in sink current from the V
C
pin. See the
Soft-Start section in Applications Information.
I
VIN
Supply Quiescent Current BIAS = 0V, FB = 1.15V, V
C
= 0.8V, SYNC = 2V 1.35 2 mA
BIAS = 5V, FB = 1.15V, V
C
= 0.8V, SYNC = 2V 0.475 1 mA
Minimum BIAS Voltage (Note 5) 2.7 3.15 V
I
BIASS
BIAS Sleep Current (Note 4) ● 110 180 µA
I
BIAS
BIAS Quiescent Current SYNC = 2V 0.75 1 mA
Minimum Boost Voltage (Note 6) I
SW
= 500mA 1.8 2.5 V
Input Boost Current (Note 7) I
SW
= 0.5A 11 16 mA
I
SW
= 0.25A 8 13 mA
V
REF
Reference Voltage (V
REF
) 3.3V < V
VIN
< 60V ● 1.212 1.25 1.288 V
V
VIN
= 80V ● 1.190 1.25 1.288 V
I
FB
FB Input Bias Current 50 200 nA
EA Voltage Gain (Note 8) 900 V/V
EA Voltage g
m
dI(V
C
)= ±10µA 650 µMho
EA Source Current FB = 1.15V 15 35 55 µA
EA Sink Current FB = 1.35V 15 30 55 µA
V
C
to SW g
m
1A/V
V
C
Switching Threshold V
SYNC
= 2V 500 mV
V
C
High Clamp 1.5 1.75 2.1 V
I
PK
SW Current Limit ● 400 650 900 mA
SW V
CESAT
Switch Saturation Voltage I
SW
= 250mA ● 200 400 mV
(Note 9) I
SW
= 500mA ● 400 800 mV
Switching Frequency ● 140 200 240 kHz
Maximum Duty Cycle 95 %
Minimum SYNC Amplitude 1.5 2 V
SYNC Frequency Range 240 500 kHz
SYNC Input Impedance 50 kΩ
I
CSS
C
SS
Current Threshold (Note 10) FB = 0V 4 10 16 µA
The ● denotes the specifications which apply over the –40°C to 140°C
temperature range, otherwise specifications are at T
J
= 25°C. V
IN
= 12V, SHDN = 12V, BIAS = 5V, FB = 1.25V, C
SS
/SYNC = 0V unless
otherwise noted.
ELECTRICAL CHARACTERISTICS