LT3574IMS#PBF Linear Technology, LT3574IMS#PBF Datasheet - Page 5

• Manufacturer Part Number: LT3574IMS#PBF
• Description: IC PWM FLYBCK ISO CM 16MSOP
• Manufacturer: Linear Technology
• Type: Flyback, Isolated, PWM - Current Moder

Specifications of LT3574IMS#PBF

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: Adj to 60V
• Current - Output: 650mA
• Frequency - Switching: 40kHz ~ 1MHz
• Voltage - Input: 3 ~ 40 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: *
• Package / Case: 16-MSOP
• Voltage - Supply: 3 V ~ 40 V
• Frequency-max: 1MHz
• Duty Cycle: 52%
• Pwm Type: Current Mode
• Buck: No
• Boost: No
• Flyback: Yes
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

pin Functions
BIAS: Bias Voltage. This pin supplies current to the switch
driver and internal circuitry of the LT3574. This pin must
be locally bypassed with a capacitor. This pin may also be
connected to V
≤ 15V. If a third winding is used, the BIAS voltage should
be lower than the input voltage for proper operation.
GND: Ground.
R
connected to the transformer primary (V
of this resistor to the R
bandgap reference, determines the output voltage (plus
the effect of any non-unity transformer turns ratio). The
average current through this resistor during the flyback
period should be approximately 200µA. For nonisolated
applications, this pin should be connected to V
R
should be tied to this pin to ground to set the current
limit. Use a 10k resistor for the full current capabilities
of the switch.
R
Resistor. This resistor should be in the range of 6k, but
for convenience, need not be precisely this value. For
nonisolated applications, a traditional resistor voltage
divider may be connected to this pin.
SHDN/UVLO: Shutdown/Undervoltage Lockout. A resistor
divider connected to V
minimum input voltage at which the LT3574 will operate.
At a voltage below ~0.7V, the part draws no quiescent
current. When below 1.22V and above ~0.7V, the part will
draw 10µA of current, but internal circuitry will remain
off. Above 1.22V, the internal circuitry will start and a 7µA
current will be fed into the SS pin. When this pin falls
below 1.22V, 2.5µA will be pulled from the pin to provide
programmable hysteresis for UVLO.
FB
ILIM
REF
: Input Pin for External Feedback Resistor. This pin is
: Input Pin for External Ground-Referred Reference
: Maximum Current Limit Adjust Pin. A resistor
IN
if a third winding is not used and if V
IN
is tied to this pin to program the
REF
resistor, times the internal
SW
). The ratio
IN
.
IN
SS: Soft-Start Pin. Place a soft-start capacitor here to
limit start-up inrush current and output voltage ramp
rate. Switching starts when the voltage at this pin reaches
~0.7V.
SW: Collector Node of the Output Switch. This pin has
large currents flowing through it. Keep the traces to the
switching components as short as possible to minimize
electromagnetic radiation and voltage spikes.
T
a resistor to ground to produce a current proportional to
absolute temperature to be sourced into the R
I
TEST: This pin is used for testing purposes only and must
be connected to ground for the part to operate properly.
VC: Compensation Pin for Internal Error Amplifier. Connect
a series RC from this pin to ground to compensate the
switching regulator. A 100pF capacitor in parallel helps
eliminate noise.
V
start-up circuitry and as a reference voltage for the DCM
comparator and feedback circuitry. This pin must be locally
bypassed with a capacitor.
TC
C
IN
: Output Voltage Temperature Compensation. Connect
: Input Voltage. This pin supplies current to the internal
= 0.55V/R
TC
.
LT3574
REF
node.

3574f