1-1-2 Switching Mode Regulator ICs
STA820M Series
Separate Excitation Switching Mode Regulator ICs with Flywheel Diode
sFeatures
• Output current: 3A
• High efficiency: TYP 83% (STA821M)
• Built-in flywheel diode (Schottky-barrier diode)
• Requires only 3 discrete components: output
coil, input and output capacitors
• Phase correction and output voltage
adjustment performed internally
• Built-in reference oscillator (110kHz)
• Built-in foldback-overcurrent and thermal
protection circuits
• Built-in ON/OFF circuit (soft start available)
sLineup
Part Number
STA821M
Output Voltage (V)
5
Output voltage: 3.3V, 9V, 12V; adjustable types currently being planned
sAbsolute
Maximum Ratings
*1
Parameter
DC Input Voltage
Output Current
Power Dissipation
*2
Junction Temperature
Storage Temperature
Thermal Resistance (Junction to Case)
Thermal Resistance (Junction to Ambient Air)
Symbol
V
IN
I
O
P
D1
P
D2
T
j
T
stg
Ratings
31
3
18.2 (With infinite heatsink)
2.7 (Without heatsink, stand-alone operation)
+125
–40 to +125
5.5
37
Unit
V
A
W
W
°C
°C
°C/W
°C/W
sApplications
• Power supplies for telecommunication
equipment
• On-board local power supplies
• OA equipment
• For stabilization of the secondary-side output
voltage of switching power supplies
θ
j-c
θ
j-a
*1: The absolute maximum ratings show the destructive limit. No parameter should exceed the ratings in transient or
normal operations.
*2: Limited by thermal protection.
sRecommended
Operating Conditions
*1
Ratings
Parameter
DC Input Voltage Range
Output Current Range
*2
Operating Junction Temperature Range
Ambient Temperature Range
*2
Symbol
min.
V
IN
I
O
T
jop
T
op
7
0
–30
–30
STA821M
max.
30
3
+125
+80
V
A
°C
°C
Unit
*1: The recommended operating conditions show the operating conditions required for the normal circuit function described in the electrical characteristics. These conditions must be
followed in actual use.
*2: Limited by T
a
-P
D
characteristics.
sElectrical
Characteristics
Ratings
Parameter
Symbol
min.
Output Voltage
Efficiency
*1
Oscillation Frequency
Line Regulation
Load Regulation
Temperature Coefficient of Output Voltage
Overcurrent Protection Starting
Current
ON/OFF
Terminal
*2
Low Level Voltage
Outflow Current
at Low Voltage
V
O
Conditions
4.8
STA821M
typ.
5.0
V
IN
=20V, I
O
=1A
83
V
IN
=20V, I
O
=1A
110
V
IN
=20V, I
O
=1A
40
V
IN
=10 to 30V, I
O
=1A
10
V
IN
=20V, I
O
=0.5 to 1.5A
±0.5
3.1
V
IN
=20V
0.2
15
25
V
SSL
=0.2V
4
V
IN
=20V, I
O
=0A
35
40
100
max.
5.2
(T
a
=25°C)
Unit
V
%
kHz
mV
mV
mV/
°C
A
V
η
Conditions
f
O
Conditions
V
Line
Conditions
V
Load
Conditions
∆V
O
/∆T
I
S
Conditions
V
SSL
I
SSL
Conditions
I
q
Conditions
µ
A
µ
A
Quiescent Circuit Current
*1: Efficiency is calculated from the following formula.
η
(%) =
V
O
·I
O
V
IN
·I
IN
×
100
*2: Pin 7 is the ON/OFF pin. Soft start at power on can be performed by connecting a
capacitor to this pin. The output can also be turned ON/OFF with this pin. The output is
stopped by setting the voltage of this pin to V
SSL
or lower. ON/OFF-pin voltage can be
changed with an open-collector drive circuit of a transistor. When using both the soft-start
and ON/OFF functions together, the discharge current from C
3
flows into the ON/OFF
control transistor. Therefore, limit the current securely to protect the transistor if C
3
capacitance is large. The ON/OFF pin is pulled up to the power supply in the IC, so
applying the external voltage is prohibited. If this pin is not used, leave it open.
STA821M
STA821M
STA821M
7 ON/OFF
7 ON/OFF
C
3
7 ON/OFF
C
3
V
O.
ON/OFF
Soft start
Soft start
+V
O.
ON/OFF
78
ICs
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