SC4503TSKTRT Semtech, SC4503TSKTRT Datasheet - Page 12

• Manufacturer Part Number: SC4503TSKTRT
• Description: IC SW REG STEP-UP 1.4A TSOT23-5
• Manufacturer: Semtech
• Type: Step-Up (Boost), Sepicr

Specifications of SC4503TSKTRT

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: Adj to 27V
• Current - Output: 1.4A
• Frequency - Switching: 1.3MHz
• Voltage - Input: 2.5 ~ 20 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: TSOT-23-5, TSOT-5, TSOP-5
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Other names: SC4503TSKTR

The minimum
graph “Switch Current Limit vs. Shutdown Pin Voltage” in
the “Typical Characteristics” shows that the
voltage needs to be at least 2V for the SC4503 to deliver
its rated power. The effect of the
SC4503 is analog between 1.4V and 2V. Within this range
the switch current limit is determined not by ILIM but in-
stead by the PWM signal path (see Figure 2). Moreover it
varies with duty cycle and the shutdown pin voltage.
 2007 Semtech Corp.
POWER MANAGEMENT
Applications Information (Cont.)
Figure 5.
SHDN SS
SHDN
End of Soft-start
V
Methods of Driving the Shutdown Pin and Soft-starting the SC4503
(a) Directly Driven from a Logic Gate. R
(b) Soft-start Only,
(c) Driven from a Logic Gate with Soft-start,
(d) Driven from a Logic Gate with Soft-start (1.7V < V
(e) Driven from an Open-collector NPN Transistor with Soft-start and
(f) Driven from a Logic Gate (whose V
SS
SHDN/SS
V
OL
voltage for switching is 1.4V. The
< 0.4V
> 2V
V IN
V
V
OH
OL
< 0.4V
> 2V
R
C
SS
SS
End of Soft-start
V
R
SHDN/SS
SS
SHDN SS
SHDN
R
> 2V
I
LIM
SHDN/SS
C
SS
SS
(a)
(c)
(e)
voltage on the
IN
SHDN/SS
IN
SHDN/SS
IN
SHDN/SS
SHDN SS
SHDN
SC4503
SC4503
SC4503
SS
pin
12
OH
LIM
Pulling the
drawing less than 1µA from the input power supply. For
voltages above 2V and below 0.4V, the
regarded as a digital on/off input. Figure 5 shows several
ways of interfacing the control logic to the shutdown pin. In
Figure 5(a) soft-start is not used and the logic gate drives
the shutdown pin through a small ( ≈ 1kΩ ) optional resistor
R
> V
SS
Limits the Gate Output Current during Fault,
. R
IN
) with Soft-start.
1.7V < V
SS
limits the current drawn by the SC4503 internal
V
End of Soft-start
V
V
OL
SHDN/SS
OH
SHDN SS
SHDN
OH
≈ 0
< 2V
> V
OH
CMDSH-3
IN
> 2V
V IN
< 2V),
D
V IN
V IN
SS
SS
1N4148
R
SS
pin below 0.4V shuts down the SC4503,
R
C
C
SS
I
SHDN/SS
SS
SS
R
SS
C
SS
(b)
(d)
(f)
IN
IN
SHDN/SS
IN
SHDN/SS
SHDN/SS
SC4503
SC4503
SC4502
SHDN SS
SHDN
www.semtech.com
SC4503
SS
pin can be