Agamem AA18380SP Switching regulator controller Datasheet

Agamem Microelectronics Inc.
PRELIMINARY
AA18380
Switching Regulator Controller
■OVERVIEW
The AA18380 is a single-channel PWM DC-DC regulator control IC that supports low-voltage operation. This
IC features a low minimum operating voltage of 1.8 V and low current consumption, is optimal for use in
high-efficiency power supplies for portable electronic equipment.
■FEATURES
• Wide operating supply voltage range: 1.8 V to 15 V
• Stable reference voltage circuit: 1.25V.
• Low current consumption: Typically 5.5 mA in operation, 1 µA or less in stand-by
• Wide PWM output frequency range: 10 kHz to 1 MHz
• Incorporates a soft start circuit and adjustable soft start time.
• Timer latch short-circuit protection circuit (SCP).
• Low input voltage malfunction prevention circuit (U.V.L.O.)
• On/off control function
• Totem-pole type output by using an external resistor to set the output current (for NPN transistors)
■PIN Configuration
(TOP VIEW)
○
IN-
1
SCP
2
7 OSC
VCC
3
6 GND
BR/CTL
4
5 OUT
8 FB
■APPLICATIONS
• LCD Displays
• PDAs
• Digital Still Cameras
• Hand-held and portable instruments
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AA18380
Agamem Microelectronics Inc.
PRELIMINARY
Switching Regulator Controller
■PIN DESCRIPTIONS
Pin No.
Symbol
I/O
Description
1
IN-
I
2
SCP
—
Soft start and short circuit protection setting capacitor connection pin
3
VCC
—
IC power supply pin
4
BR/CTL
I
Output current setting and control pin
5
OUT
O
Output voltage monitoring pin
6
GND
—
7
OSC
—
8
FB
O
Ground pin
Timing capacitor & resistor connection pin for setting the internal PWM
frequency
Error amplifier output pin
Internal error amplifier inverting input pin
■BLOCK DIAGRAM
Vcc
OSC
3
7
Reference
Voltage Supply
1.25V
0.8V
Sawtooth wave
Oscillator
0.1V
0.1V
IN-
Error
Amp.
+
1
0.5V
FB
5 OUT
+ PWM
COMP.
+
+
36KΩ
500Ω
Output drive
Control circuit
30KΩ
0.3V
DTC 0.6V
8
Soft start SCP
6
2
4
GND
SCP
BR/CTL
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Agamem Microelectronics Inc.
PRELIMINARY
AA18380
Switching Regulator Controller
■ABSOLUTE MAXIMUM RATINGS
(Ta = +25°C)
Parameter
Symbol
Rating
Condition
Unit
Min
Max
—
16
V
—
–50
mA
—
50
mA
Power supply voltage
VCC
Output source current
IO+
Output sink current
IO –
Allowable dissipation
PD
Ta ≤ +25° C
—
430*
mW
Operating temperature
Top
—
–30
+85
Storage temperature
Tstg
–55
+125
°C
°C
—
WARNING: Semiconductor devices can be permanently damaged by application of stress (voltage, current,
temperature, etc.) in excess of absolute maximum ratings. Do not exceed these ratings.
■RECOMMENDED OPERATING RANGE
(Ta = +25°C)
Parameter
Value
Symbol
Unit
Min
Typ
Max
VCC
1.8
—
15
V
VI
–0.2
—
1.0
V
BR/CTL pin input voltage
VBR
–0.2
—
VCC
V
Output source current
IO+
–40
—
—
mA
Output sink current
IO –
—
—
40
mA
SCP pin capacitance
CPE
—
0.1
—
µ F
Phase compensation capacitance
CP
—
0.1
—
µ F
Output current setting resistance
RB
150
390
5000
Ω
Timing resistance
RT
1.0
3.0
10.0
kΩ
Timing capacitance
CT
100
270
10000
pF
Oscillation frequency
fOSC
10
500
1000
kHz
Operating temperature
TOP
–30
+25
+85
°C
Power supply voltage
Error amplifier input voltage
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AA18380
Agamem Microelectronics Inc.
PRELIMINARY
Switching Regulator Controller
■ELECTRICAL CHARACTERISTICS
(VCC = +2 V, Ta = +25° C)
Parameter
Circuit to prevent
malfunction at low
input voltage
(U.V.L.O.)
Symbol
Value
Condition
Unit
Min
Typ
Max
—
—
0.9
V
1.1
1.3
1.5
V
–1.5
–1.0
–0.7
µ A
0.7
0.8
0.9
V
–1.5
–1.0
–0.7
µ A
Reset voltage
VR
Threshold voltage
VTH
Charging current
ICS
Soft start
Voltage at soft start
completion
VtS
Short circuit
detection (S.C.P.)
Charging current
ICPC
Threshold voltage
Oscillation
frequency
Frequency input
stability
VtPC
—
0.7
0.8
0.9
V
fOCS
RT = 3.0 kΩ , CT = 270 pF
400
500
600
kHz
fdV
VCC = 2 V to 15 V
—
2
10
%
Frequency variation
with temperature
fdT
Ta = –30°C to +85°C
—
5
—
%
Input threshold
voltage
VT
VFB = 450 mV
480
500
520
mV
VT input stability
VTdV
VCC = 2 V to 15 V
—
5
20
mV
VT variation with
temperature
VTdT
Ta = –30°C to +85°C
—
1
—
%
Input bias current
IB
–1.0
–0.2
1.0
µ A
Voltage gain
Frequency
bandwidth
AV
70
100
145
V/V
—
6
—
MHz
0.78
0.87
—
V
—
0.05
0.2
V
—
–40
–24
µ A
24
40
—
µ A
65
75
85
%
Sawtooth wave
oscillator (OSC)
Error amplifier
Idle period
adjustment
section
Maximum output
voltage range
BW
VSCP = 0 V
—
VSCP = 0 V
VIN = 0 V
—
AV = 0 dB
VOM+
—
VOM –
Output source
current
Output sink current
IOM –
Maximum duty cycle
tDUTY
©Copyright Agamem Microelectronics Inc.
—
IOM+
VFB = 0.45 V
RT = 3.0 kΩ , CT = 270 pF
VFB = 0.8 V
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AA18380
Agamem Microelectronics Inc.
PRELIMINARY
Switching Regulator Controller
(Continued)
Parameter
Symbol
Output voltage
Output section
Output current
setting section/
Control section
Entire device
Value
Condition
Unit
Min
Typ
Max
VOH1
RB = 390 Ω , IO = –15 mA
1.0
1.2
—
V
VOH2
RB = 750 Ω , VCC = 1.8 V
IO = –10 mA
0.8
1.0
—
V
VOL1
RB = 390 Ω , IO = 15 mA
—
0.1
0.2
V
VOL2
RB = 750 Ω , VCC = 1.8 V
IO = 10 mA
—
0.1
0.2
V
Output source
current
Output sink current
IO+
RB = 390 Ω , VO = 0.9 V
—
–30
–20
mA
IO –
RB = 390 Ω , VO = 0.3 V
30
60
—
mA
Pull down resistance
RO
20
30
40
kΩ
Pin voltage
VBR
0.2
0.3
0.4
V
Input off condition
IOFF
–20
—
0
µ A
Input on condition
ION
—
—
–45
µ A
Pin current range
IBR
–1.8
—
–0.1
mA
Stand-by current
ICCS
BR/CTL pin open or VCC
—
—
1
µ A
Average supply
current
ICC
RB = 390 Ω
—
5.5
9.3
mA
—
RB = 390 Ω
—
■ TIMING DIAGRAM
FB Pin voltage
Reference input for short
circuit detectioin compartor
Idle Period setting voltage
Sawtooth wave output
Soft start setting voltage
Out put waveform
Stable State
SCP pin waveform
Soft start
tS
Output
Short
circuit
ON-Power supply control SW
OFF
©Copyright Agamem Microelectronics Inc.
tPE
Output short circuit
Short circuit
detection
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Agamem Microelectronics Inc.
PRELIMINARY
AA18380
Switching Regulator Controller
■TYPICAL CHARACTERISTICS
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Agamem Microelectronics Inc.
PRELIMINARY
©Copyright Agamem Microelectronics Inc.
AA18380
Switching Regulator Controller
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Agamem Microelectronics Inc.
PRELIMINARY
©Copyright Agamem Microelectronics Inc.
AA18380
Switching Regulator Controller
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Agamem Microelectronics Inc.
PRELIMINARY
AA18380
Switching Regulator Controller
■HOW TO SET THE TIME CONSTANT FOR SOFT START AND SHORT CIRCUIT DETECTION
1. Soft Start
A soft start function, which gradually increases the width of the output pulses at power on, will be applied if a
capacitor is connected to the SCP pin. This can prevent rush currents and overshoot when the power supply is
turned on.
At power on, the capacitor CPE connected to the SCP pin starts charging. The PWM comparator compares the
soft start setting voltage as a proportion of the voltage at the SCP pin with the sawtooth waveform. The
comparison controls the ON duty of the OUT pin, causing the soft start operation. On completion of soft start
operation, the voltage at the SCP pin stays low, the soft start setting voltage stays high, and the circuit enters the
output short circuit detection wait state.
Soft start time (The time until the output ON duty reaches approximately 50%)
tS [s] = 0.35 × CPE [µF]
2. Timer Latch Short Circuit Protection
When the load conditions suddenly change due to load effect, the short-circuit protection comparator outputs the
+
high-level signal (VOM ) and the capacitor CPE connected to the SCP terminal starts charging. When the external
capacitor CPE has been charged to approximately 0.8V, the latch circuit is set, the output terminal is fixed to low
level, and the dead-time is set to 100%. However, the latch circuit is not reset unless the power for the latch
circuit is turned off or restarted by the on/off control.
• Short circuit detection time
tPE [s] = 0.8 × CPE [µF]
■FUNCTIONAL DESCRIPTION
1. Switching Regulator Function
(1) Reference voltage circuit
This circuit is composed of a band gap circuit, and outputs a 1.25-volt temperature compensated reference
voltage. This reference voltage is stabilized when the supply voltage is 1.8 V or higher. In addition to providing
the reference voltage for the switching regulator, the circuit also sets the idle period.
(2) Sawtooth wave oscillator
This circuit generates a triangular wave like sawtooth with a peak of 0.8V (VOSCH) and a trough of 0.1V (VOSCL)
using a capacitor (for the time constant) and resistor connected to the OSC pin (pin 7). The oscillator frequency
can be set to any value by selecting appropriate values for the external capacitor and resistor, CT and RT. This
oscillator can provide a frequency in the range 10 kHz to 1 MHz.
fOSC =
-1
VOSCL
CT × RT × ln
VOSCH
1
CT × RT
= 0.48×
[HZ]
(3) Error amplifier
This error amplifier detects and amplifies the DC-DC converter output voltage, and inputs that signal to a PWM
comparator. The 0.5 V internal reference voltage is applied to the non-inverting input. Arbitrary gain and phase
compensation can be connected by inserting a resistor and capacitor in series between the error amplifier output
pin (pin 8) and the inverting input pin (pin 1).
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AA18380
Agamem Microelectronics Inc.
PRELIMINARY
Switching Regulator Controller
(4) PWM comparator
The voltage comparator has one inverting and three non-inverting inputs. The comparator is a voltage/pulse
width converter that controls the on-period of the output pulse according to its input voltage. The output
transistors are turned on during periods when the OSC pin (pin 7) triangular waveform is lower than the error
amplifier output voltage, soft start setting voltage, and idle period setting voltage.
(5) Output driver
The output circuit has a totem pole structure. A constant-current source output with line regulation can be set up
at an arbitrary voltage by connecting a current setting resistor to the BR/CTL pin (pin 4).
2. Power Supply On/Off Function
Stand-by mode (supply current 1 µA or less) can be set by connecting the BR/CTL pin (pin 4) to VCC or by
making the pin open circuit.
SW
Mode
AA18380
OFF
Stand-by mode
4
RB
ON
SW
Operating mode
3. Other Functions
(1) Soft start and short circuit detection
Soft start operation can be set by connecting capacitor CPE to the SCP pin (pin 2). Soft start prevents current
spike and overshoot.
When the soft start operation completes, the AA18380 enters the normal mode and enable short circuit detection
function. When the output voltage drops, the error amplifier output is fixed at VOM+ and capacitor CPE starts
charging. When it charges to above 0.8V, the output pin (pin 5) is set low and the SCP pin (pin 2) stays low.
Once the protection circuit operates, the output latch circuit will not reset until power is restarted. (See “■ HOW
TO SET THE TIME CONSTANT FOR SOFT START AND SHORT CIRCUIT DETECTION”.)
(2) Circuit to prevent malfunction at low input voltage
This circuit protects the system against degradation or destruction due to incorrect control operation when the
power supply voltage falls during power on or power off.
The low input voltage malfunction prevention circuit detects the internal reference voltage that changes with the
supply voltage level. While the supply voltage is rising, On detection, the circuit fixes the output pin to low. The
system recovers when the supply voltage rises back above the threshold voltage of the malfunction prevention
circuit.
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AA18380
Agamem Microelectronics Inc.
PRELIMINARY
Switching Regulator Controller
■TYPICAL APPLICATION EXAMPLE
Boost Type - Step Up
SCP
Vcc
BR/CTL
8
2
3
4
7
6
5
C1
0.1uF R6
390Ω
Q2
2N7002
CTL-IN
Vin
(3V)
C3
33uF
1
AA18380
IN-
L1
22uH
FB
Vout
(5V)
1N5821
OSC
D1
GND
R1 18KΩ
OUT
C6
10uF
Q1
FZT489
C5
270pF
C4
0.1uF
R5
3KΩ
R2
2KΩ
Vout = 0.5 X (1 + R1/R2)
Vout
(5V)
Buck Type - Step Down
2SA1585S 22uH
470Ω
1
SCP 2
Vcc 3
BR/CTL
Vin
(12V)
4
8
AA18380
33uF
IN-
7
6
FB
2N3904
20KΩ
OSC
2KΩ
47uF
GND
FR154
R2
5 OUT
2N3904
0.1uF
4.7KΩ
R1
9KΩ
68pF
104pF
1KΩ
0.1uF
270pF
3KΩ
1.bootstrap, single end push pull style.
2.Vout = 0.5 X (1 + R1/R2)
3.For example, R1=5.6KΩ, R2=1KΩ, Vout=3.3V
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Agamem Microelectronics Inc.
PRELIMINARY
AA18380
Switching Regulator Controller
■PC Board Layout Guideline
PCB layout is very important for DC-DC operation. Please follow the notes and sample layout below.
• Create a power ground island consisting of the input and output capacitor grounds and GND pins.
Connect all of these together with short, wide traces or a small ground plane and isolate the IC
ground from the power system.
• Make the lines in the high-current loop as wide as possible and placing the inductor, rectifier diode,
and output capacitors near the input capacitors and near the OUT and GND pins.
• Position the input filter capacitor C3 as close as possible to the VCC and ground pins, and assure
that there are no other paths for switching noise to enter the IC.
• Keep the length of the line between the OUT pin and the switching device (MOSFET or other
transistor) as short as possible to provide a clean switching pulse to the switching device.
• The inductor and rectifier diode need to be close with OUT pin.
• Place the feedback resistor – R2 as close to the IN1- pin as possible. The divider’s center trace
should be kept short. Placing the resistors far away causes picking up switching noise. Avoid running
the feedback trace near OUT pin.
• Minimize the length and maximize the width of the traces between the output capacitors and the load
for best transient responses. (Please refer to boost type application circuit for this PCB layout sample.)
■NOTES ON USE
• The information described herein is subject to change without notice.
• The specifications for the product described in this document are for reference only. Upon actual use,
therefore, please request that specifications to be separately delivered.
•The application circuit examples explain typical applications of the products, and do not guarantee the success
of any specific mass-production design.
• Application circuit diagrams and circuit constants contained herein are shown as examples of standard use
and operation. Please pay careful attention to the peripheral conditions when designing circuits and deciding
upon circuit constants in the set.
• Take account of common impedance when designing the earth line on a printed wiring board.
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AA18380
Agamem Microelectronics Inc.
PRELIMINARY
Switching Regulator Controller
■ORDERING INFORMATION
Part number
AA18380AP
AA18380SP
Package
8-pin Plastic TSSOP
8-pin Plastic SOP
Remarks
■PACKAGE DIMENSIONS
AA18380AP - 8-pin Plastic TSSOP
E1
E
L
C
AA18380AP
theta
D
SYMBOLS
A
A1
A2
b
C
D
E
E1
e
L
y
theta
DIMENSIONS IN MILLIMETERS
MIN
NOM
MAX
----1.20
0.05
--0.15
1.05
1.00
0.80
0.30
--0.19
0.20
--0.09
3.00
3.10
2.90
6.40
6.60
6.20
4.40
4.50
4.30
0.65
----0.60
0.75
0.45
--0.10
----8°
0°
A2
A1
A
12°(4X)
e
b
DIMENSIONS IN INCHES
MIN
NOM
MAX
----0.048
0.002
--0.006
0.041
0.039
0.031
0.012
--0.007
0.008
--0.004
0.118
0.122
0.114
0.252
0.260
0.244
0.173
0.177
0.169
0.026
----0.024
0.030
0.018
--0.004
----8°
0°
NOTE
1. PACKAGE BODY SIZES EXCLUDE MOLD FLASH PROTRUSIONS OR GATE
BURRS
2. TOLERANCE +/-0.1 mm UNLESS OTHERWISE SPECIFIED
3. COPLANARITY : 0.1 mm
4. CONTROLLING DIMENSION IS MILLIMETER. CONVERTED INCH DIMENSIONS
ARE NOT NECESSARILY EXACT.
5. FOLLOWED FROM JEDEC MO-153
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Agamem Microelectronics Inc.
PRELIMINARY
©Copyright Agamem Microelectronics Inc.
AA18380
Switching Regulator Controller
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