The SM8172A is a 2-output power supply IC that incorporates a step-down DC/DC converter and series regu-
lator with built-in reset circuit. The DC/DC converter is a PWM-type synchronous rectifier. The SM8172A has
soft start, overcurrent detection, supply undervoltage lockout, and thermal shutdown circuits built-in, making it
ideal as a supply voltage source IC for large-scale LSIs that operate from a 5V supply.
2. FEATURES
I
I
I
I
Input voltage range: 4.5 to 5.5V
Standby current: 0.01
µ
A (typ)
Series regulator
• Feedback-type current limiter to reduce output
current when outputs are short-circuit
• Output voltage: 3.3V
(available for optional setting from 2.1 to 3.6V
by 0.1V-step)
• Maximum output current: 450mA
• Voltage accuracy:
±
2% (VIN = 5.0V, Ta = 25
°
C)
DC/DC converter
• Current-mode operation for excellent transient
response
• Output voltage: 0.8 to 1.8V
(typ, selectable by external resistor)
• Maximum output current: 900mA
• Operating frequency: 2MHz (typ)
• Voltage accuracy:
±
2%
(FB pin, VIN = 5.0V, Ta = 25
°
C, DCOUT = 1.0V)
I
I
I
Reset circuit built-in
• Reset detection voltage: 3.7V (typ)
(available for optional setting from 3.2 to 4.2V
by 0.1V-step)
• Reset return delay time: 65ms (typ)
(50ms, 32ms, 16ms, and 8ms selectable with
option)
Various protection circuit built-in
• Startup soft start circuit built-in
• Overtemperature thermal shutdown (TSD) circuit
built-in
• Supply undervoltage lockout (UVLO) circuit
built-in
Package: 10-pin SON
3. APPLICATIONS
I
I
I
I
ODD
DVD player/recorder
Next-generation DVD player/recorder
Electronic equipment
4. TYPICAL APPLICATION CIRCUIT
5.0V
VIN1
C1
10µF
PGND
RESETN
R3
10kΩ
RESETN output
VIN2
C2
10µF
GND
LDOUT
C5
3.3µF
R2
330kΩ
ENDCO
Regulator control
ENLDO
LX
FB
C3
8pF
L
2.2µH
R1
220kΩ
DCOUT
(1.0V)
Regulator output
DC/DC control
C4
4.7µF
Note. RESETN is open-drain, therefore, please take care so that the High level signal does not exceed the absolute maximum rating of IC which receives
the reset signal. Besides, if the rest signal is not used, RESETN should be connected to GND.
5. ORDERING INFORMATION
Device
SM8172AD
Package
10-pin SON
SEIKO NPC CORPORATION —1
SM8172A
6. PINOUT
(Top view)
VIN2
1
LDOUT
2
GND
3
ENDCO
4
ENLDO
5
10
RESETN
9
8
7
6
FB
VIN1
LX
PGND
7. PIN DESCRIPTION
Number
1
2
3
4
5
6
7
8
9
10
Name
VIN2
LDOUT
GND
ENDCO
ENLDO
PGND
LX
VIN1
FB
RESETN
I/O
–
O
–
Ip
*3
Ip
*3
–
O
–
I
O
Series regulator output
*2
Ground (internal circuits)
Output enable (DC/DC converter)
Output enable (series regulator)
Ground (DC/DC converter output circuit)
DC/DC converter coil drive
*4
Supply voltage (DC/DC converter output circuit)
*1
DC/DC converter feedback connection
*5
Reset signal output (active-LOW, open-drain output)
*6
Function
Supply voltage (series regulator, internal circuits)
*1
*1. VIN1 and VIN2 should have the same voltage potential.
*2. When the series regulator is not used, LDOUT pin should be open and not be connected to GND.
*3. Ip = Input with pull-down resistor built-in
*4. When the DC/DC converter is not used, LX pin should be open and not be connected to GND or the supply.
*5. When the DC/DC converter is not used, FB pin should be connected to GND.
*6. When the reset signal is not used, RESETN pin should be connected to GND.
8. BLOCK DIAGRAM
10kΩ
5.0V
VIN2
detector
VIN2
GND
Current
protection
Soft
start
Vref
ENDCO
ENLDO
OSC
Soft
start
Current
protection
Current mode
PWM control
VIN1
5.0V
8pF
LX
10µF
2.2µH
4.7µF
PGND
DCOUT
(1.0V)
220kΩ
Thermal
protection
+
−
Delay
circuits
RESETN output
RESETN
10µF
ERR
+
LDOUT
3.3µF
LDOUT output
(3.3V)
ERR
−
FB
330kΩ
Output
control
SEIKO NPC CORPORATION —2
SM8172A
9. ABSOLUTE MAXIMUM RATINGS
Parameter
Supply voltage range
Input pin voltage range
Output pin voltage range 1
Output pin voltage range 2
LX output current
LDOUT output current
Power dissipation
Junction temperature
Storage temperature range
Symbol
V
IN
V
ENDCO
, V
ENLDO
, V
FB
V
LX
, V
LDOUT
V
RESETN
I
LX
I
LDOUT
P
D
T
JMAX
T
stg
Rating
−
0.3 to 6.0
−
0.3 to V
IN
+ 0.3
−
0.3 to V
IN
+ 0.3
−
0.3 to 6.0
1.5
700
2000 (Ta = 25
°
C)
*1
+125
−
55 to +125
Unit
V
V
V
V
A
mA
mW
°
C
°
C
*1. 101.5
×
105.0
×
1.6mm, wiring ratio 250%, FR-4, 4-layer board (thermal vias, die pad connections)
Note that the ratings will vary depending on the board specifications, footprint pattern, and other factors.
Note. The device may be damaged or deteriorated if any of the above parameter ratings is exceeded.
2500
Power dissipation P
D
[mW]
2000
1500
1000
500
0
0
25
50
75
Ambient temperature Ta [°C]
10. RECOMMENDED OPERATING CONDITIONS
Rating
Parameter
Supply voltage
Operating ambient temperature
Pin
VIN1, 2
−
Symbol
V
IN
Ta
Conditions
min
VIN1 = VIN2
4.5
−
20
typ
5.0
+25
max
5.5
+85
V
°
C
Unit
SEIKO NPC CORPORATION —3
SM8172A
11. ELECTRICAL CHARACTERISTICS
Note. The specifications of “ELECTRICAL CHARACTERISTICS” are shown by using “TYPICAL APPLI-
CATION CIRCUIT” on page 13.
11-1. Common Blocks
VIN1 = VIN2 = 5.0V, GND = PGND = 0V, Ta = 25
°
C unless otherwise noted.
Rating
Parameter
Standby current
HIGH-level input voltage
LOW-level input voltage
HIGH-level input current
RESETN output current
Reset circuit operating
voltage
Reset circuit return delay
time
Under voltage lockout
TSD operating temperature
TSD hysteresis
RESETN
VIN2
RESETN
VIN2
–
–
ENDCO,
ENLDO
Pin
VIN1, 2
Symbol
I
STB
V
IH
V
IL
I
IH
I
RESETN
V
RESETNL
V
RESETNH
t
RESETN
V
UVLOL
V
UVLOH
T
SD
T
SDHYS
V
RESETN
= 1.0V
When VIN falls
When VIN rises
When VIN rises
When VIN falls
When VIN rises
Condition
min
Standby mode (ENDCO = ENLDO = L),
No load on inputs/outputs
–
1.8
–
–
20
3.5
3.7
–
2.7
2.9
–
–
typ
0.01
–
–
5.0
–
3.7
3.9
65
3.0
3.2
170
20
max
1
–
0.6
10
–
3.9
4.1
–
3.3
3.5
–
–
µ
A
V
V
µ
A
mA
V
V
ms
V
V
°
C
°
C
Unit
11-2. Series Regulator
VIN1 = VIN2 = 5.0V, GND = PGND = 0V, Ta = 25
°
C unless otherwise noted.
Rating
Parameter
Current consumption
Soft start time
Output voltage
Maximum output current
*1
Input stability
Load stability
Overcurrent protection
circuit operating current
Pin
VIN1, 2
LDOUT
LDOUT
LDOUT
LDOUT
LDOUT
LDOUT
Symbol
I
DD_LDO
t
SS_LDO
V
LDO
I
LDO
∆
V
OUT1
∆
V
OUT2
I
OS
I
LDO
= 10mA
VIN2 = 4.5V, LDOUT = 3.3V
4.5V
≤
VIN2
≤
5.5V, I
LDO
= 30mA
VIN2 = 5.0V, 1mA
≤
I
LDO
≤
300mA
No load
Condition
min
–
0.5
3.23
450
–
–
–
typ
0.1
1
3.3
–
0.1
40
700
max
0.25
2
3.37
–
0.35
–
–
mA
ms
V
mA
%/V
mV
mA
Unit
*1. The output voltage difference at I
LDO
= 1mA and I
LDO
= 450mA is within
±
3%.
SEIKO NPC CORPORATION —4
SM8172A
11-3. DC/DC Converter
VIN1 = VIN2 = 5.0V, GND = PGND = 0V, Ta = 25
°
C unless otherwise noted.
Rating
Parameter
Current consumption 1
Current consumption 2
Soft start time
*1*2
Output voltage range
*2
FB voltage
Maximum output current
*2*3
Switching frequency
Supply-side switch ON resistance
GND-side switch ON resistance
LX leakage current
Overcurrent protection circuit
operating current
Pin
VIN1, 2
VIN1, 2
–
–
FB
–
LX
LX
LX
LX
LX
Symbol
I
DD1
I
DD2
t
SS
V
DCO
V
FB
I
DCO
f
OSC
R
ONP
R
ONN
I
LEAKLX
I
LIMITLX
I
DCO
= 50mA
I
DCO
= –50mA
Standby mode, LX = 1/2VIN
Supply-side switch
Condition
min
No load, switching stopped
FB = VIN1, LX = Open
–
–
0.2
0.8
0.588
900
1.7
–
–
–1.0
–
typ
0.35
2.5
0.6
–
0.6
–
2.0
0.3
0.3
–
1.5
max
0.75
5.5
1.0
1.8
0.612
–
2.3
–
–
1.0
–
mA
mA
ms
V
V
mA
MHz
Ω
Ω
µ
A
A
Unit
*1. The soft start time is the interval during which the output current is limited internally in the IC, and is different from the DC/DC converter output raise
time. If the maximum load current is output after soft start time startup, the output voltage does not fall. But, if the maximum load current is output
before soft start time startup, it should be careful that the output voltage may fall.
LX switching start
High
ENDCO
Low
1.5A (typ)
Current limit
Soft start time
DCOUT
1.8V
1.0V
42µsec (typ)
28µsec (typ)
The LX starts the switching operation after 42µs from ENDCO rising. After switching operation startup, the output current limit operates like linear
increase (load current = 0A). The DC/DC converter output voltage rise time varies with the load current, output capacitance, and other conditions.
模拟与混合信号
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