1-1-2 Switching Mode Regulator ICs
STA820M Series Separate Excitation Switching Mode Regulator ICs with Flywheel Diode
■Features
■Lineup
• Output current: 3A
Part Number
STA821M
Output Voltage (V)
5
• High efficiency: TYP 83% (STA821M)
• Built-in flywheel diode (Schottky-barrier diode)
Output voltage: 3.3V, 9V, 12V; adjustable types currently being planned
• Requires only 3 discrete components: output
coil, input and output capacitors
■Absolute Maximum Ratings*1
• Phase correction and output voltage
adjustment performed internally
Parameter
Symbol
Ratings
Unit
V
DC Input Voltage
VIN
31
• Built-in reference oscillator (110kHz)
Output Current
IO
3
A
PD1
PD2
Tj
18.2 (With infinite heatsink)
W
• Built-in foldback-overcurrent and thermal
protection circuits
Power Dissipation*2
2.7 (Without heatsink, stand-alone operation)
W
Junction Temperature
+125
–40 to +125
5.5
°C
• Built-in ON/OFF circuit (soft start available)
Storage Temperature
Tstg
θj-c
°C
Thermal Resistance (Junction to Case)
Thermal Resistance (Junction to Ambient Air)
°C/W
°C/W
■Applications
θj-a
37
• Power supplies for telecommunication
equipment
*1: The absolute maximum ratings show the destructive limit. No parameter should exceed the ratings in transient or
normal operations.
• On-board local power supplies
• OA equipment
*2: Limited by thermal protection.
• For stabilization of the secondary-side output
voltage of switching power supplies
■Recommended Operating Conditions*1
Ratings
Parameter
Symbol
STA821M
Unit
min.
7
max.
30
DC Input Voltage Range
Output Current Range*2
VIN
IO
V
A
0
3
Operating Junction Temperature Range
Ambient Temperature Range*2
Tjop
Top
–30
–30
+125
+80
°C
°C
*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 Ta-PD characteristics.
■Electrical Characteristics
(Ta=25°C)
Ratings
Parameter
Symbol
STA821M
Unit
min.
4.8
typ.
max.
5.2
VO
5.0
V
Output Voltage
Conditions
η
VIN=20V, IO=1A
83
Efficiency*1
%
Conditions
fO
VIN=20V, IO=1A
110
kHz
mV
mV
Oscillation Frequency
Line Regulation
Conditions
VLine
VIN=20V, IO=1A
40
100
40
Conditions
VLoad
VIN=10 to 30V, IO=1A
10
VIN=20V, IO=0.5 to 1.5A
0.5
Load Regulation
Conditions
∆VO/∆T
IS
Temperature Coefficient of Output Voltage
mV/°C
3.1
15
Overcurrent Protection Starting
Current
A
Conditions
VSSL
VIN=20V
Low Level Voltage
ON/OFF
Terminal*2
0.2
V
ISSL
25
VSSL=0.2V
4
35
Outflow Current
at Low Voltage
µA
Conditions
Iq
mA
Quiescent Circuit Current
Conditions
VIN=20V, IO=0A
*1: Efficiency is calculated from the following formula.
VO·IO
η(%) =
× 100
VIN·IIN
STA821M
STA821M
STA821M
*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 VSSL 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 C3 flows into the ON/OFF
control transistor. Therefore, limit the current securely to protect the transistor if C3
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.
7
ON/OFF
7
ON/OFF
7
ON/OFF
C3
C3
V
O. ON/OFF
Soft start
Soft start
+VO. ON/OFF
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