SM72485 Datasheet, PDF (2/16 Pages) National Semiconductor (TI) – SolarMagic 100V, 150 mA Constant On-Time Buck Switching Regulator

Connection Diagrams
Top View
8-Lead MSOP
30142303
Top View
8-Lead LLP
30142302
Ordering Information
Order Number
SM72485SDE
SM72485SD
SM72485SDX
SM72485MME
SM72485MM
SM72485MMX
Package Type
LLP-8
MSOP-8
NSC Package Drawing
SDC08A
MUA08A
Package Marking
S2485
2485
Supplied As
250 Units on Tape and Reel
1000 Units on Tape and Reel
4500 Units on Tape and Reel
250 Units on Tape and Reel
1000 Units on Tape and Reel
3500 Units on Tape and Reel
Pin Descriptions
Pin Name
Description
Application Information
1
SW Switching Node
Power switching node. Connect to the output inductor, re-circulating diode,
and bootstrap capacitor.
2
BST Boost Pin (Boot–strap capacitor An external capacitor is required between the BST and the SW pins. A 0.01
input)
µF ceramic capacitor is recommended. An internal diode charges the
capacitor from V_CC during each off-time.
3
RCL Current Limit OFF time set pin A resistor between this pin and RTN sets the off-time when current limit is
detected. The off-time is preset to 35 µs if FB = 0V.
4
RTN Ground pin
Ground for the entire circuit.
5
FB Feedback input from Regulated This pin is connected to the inverting input of the internal regulation
Output
comparator. The regulation threshold is 2.5V.
6 RT/SD On time set pin
A resistor between this pin and VIN sets the switch on time as a function of
V_IN. The minimum recommended on time is 400 ns at the maximum input
voltage. This pin can be used for remote shutdown.
7
VCC Output from the internal high This regulated voltage provides gate drive power for the internal Buck
voltage series pass regulator. switch. An internal diode is provided between this pin and the BST pin. A
local 0.47 µF decoupling capacitor is required. The series pass regulator is
current limited to 9 mA.
8
VIN Input voltage
Input operating range: 6V to 95V.
EP Exposed Pad
The exposed pad has no electrical contact. Connect to system ground plane
for reduced thermal resistance.
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