AN8013SH [PANASONIC]
Single-channel step-up or step-down DC-DC converter control IC; 单通道升压或降压型DC -DC转换器控制IC
| 型号： | AN8013SH |
| 厂家： | 
PANASONIC |
| 描述： | Single-channel step-up or step-down DC-DC converter control IC |
| 文件： | 总15页 (文件大小：126K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Voltage Regulators
AN8013SH
Single-channel step-up or step-down
DC-DC converter control IC
Unit: mm
■ Overview
The AN8013SH is a single-channel PWM DC-DC
converter control IC. This IC implements DC-DC con-
verters that provide a single arbitrary output voltage that
is either a stepped-up or stepped-down level. It features a
wide operating supply voltage range, low power, and a
built-in overcurrent protection circuit to protect the
switching transistor from damage or destruction. The
AN8013SH is provided in a 0.5 mm pitch 10-pin surface
mounting package and is optimal for use in miniature
high-efficiency portable power supplies.
1
5
10
6
0.5±0.2
4.3±0.30
6.3±0.30
■ Features
SSOP010-P-0225
• Wide operating supply voltage range (3.6 V to 34 V)
• Small consumption current (2.4 mA typical)
• Supports control over a wide output frequency range:
20 kHz to 500 kHz.
• Built-in pulse-by-pulse overcurrent protection circuit
(Detection voltage: VCC − 100 mV)
■ Pin Descriptions
CLM
RT
1
2
3
10 VCC
9
8
7
6
Out
GND
IN−
FB
CT
S.C.P. 4
DTC
• Built-in timer latch short-circuit protection circuit
(charge current 1.3 µA typical)
5
• Incorporating the under-voltage lock-out (U.V.L.O.) circuit
• Built-in reference voltage circuit (Error amplifier reference input: 0.75 V (allowance: ±4%))
• Output block is open-collector (darlington) type.
• High absolute maximum rating of output current (100 mA)
• Duty ratio with small sample-to-sample variations (55% ± 5%).
• Adopts a 0.5-mm lead pitch 10-pin small outline package
■ Applications
• Switching mode power supply units (in portable equipment and other applications)
1
AN8013SH
Voltage Regulators
■ Block Diagram
OSC
VREF
RT
PWM
9
Out
0.1 V
VREF
S
R
Latch
VREF
RT
6
7
FB
VREF
8
GND
Error amp.
0.75 V
S.C.P. comp.
1.90 V
R
0.75 V
S
R
IN−
S
Q
Latch
U.V.L.O.
■ Absolute Maximum Ratings at Ta = 25°C
Parameter
Supply voltage
Symbol
Rating
35
Unit
V
VCC
CLM pin allowable application voltage VCLM
Error amplifier allowable input voltage VIN−
35
V
−0.3 to +2.5
2.5
V
DTC pin allowable input voltage
Out pin allowable application voltage
Collector output current
VDTC
VOUT
IOUT
PD
V
35
V
100
mA
mW
°C
°C
Power dissipation (Ta = 85°C)
Operating ambient temperature
Storage temperature
154
Topr
Tstg
−30 to +85
−55 to +150
■ Recommended Operating Range at Ta = 25°C
Parameter
Supply voltage rise time (0 to 3.6 V)
Collector output voltage
Collector output current
Timing capacitance
Symbol
Min
Max
Unit
µs
tr (VCC
VOUT
IOUT
CT
)
10
34
50
V
mA
pF
100
5.1
1 800
15
Timing resistance
RT
kΩ
kHz
pF
Oscillator frequency
fOUT
CSCP
20
500
Short-circuit protection time constant setting
capacitor
1 000
2
Voltage Regulators
AN8013SH
■ Electrical Characteristics at Ta = 25°C
Parameter
U.V.L.O. block
Symbol
Conditions
Min
Typ Max Unit
Circuit operation start voltage
Hysteresis width
VUON
VHYS
2.8
3.1
3.4
V
100
200
300
mV
Error amplifier block
Input threshold voltage
VTH
Voltage follower
0.72 0.75 0.78
mV
mV
Line regulation with input fluctuation Vdv
Voltage follower,
2
8
VCC = 3.6 V to 34 V
Input bias current
IB
−500 −25
nA
V
High-level output voltage
VEH
VEL
Vdt1
2.0
Low-level output voltage
Input threshold voltage temperature
characteristics 1
0.3
V
Voltage follower,
±1
±1
%
Ta = −30°C to +25°C
Voltage follower,
Input threshold voltage temperature
characteristics 2
Vdt2
%
Ta = −25°C to +85°C
Output sink current
Output source current
Open-loop gain
ISINK
VFB = 0.9 V
8
mA
µA
dB
ISOURCE VFB = 0.9 V
−120
70
AV
PWM Comparator Block
Input threshold voltage: high
Input threshold voltage: low
Input current
VDT-H Duty: 100%
VDT-L Duty: 0%
IDTC
1.2
V
V
A
0.6
−12
−11
−10
Output block
Oscillation frequency
Output duty
fOUT
Du
RT = 15 kΩ, CT = 150 pF
185
50
205
55
225
60
kHz
%
RDTC = 91 kΩ
Output saturation voltage
Output leak current
RT pin voltage
VOL
IO = 50 mA, RT = 15 kΩ
0.9
1.2
10
V
ILEAK VCC = 34 V, when output Tr is off
VRT
µA
V
0.59
500
±1
Maximum oscillation frequency
fOUT(max) RT = 5.1 kΩ, CT = 120 pF
kHz
%
Frequency supply voltage
characteristics
fdV
fdT1
fdT2
fOUT = 200 kHz,
VCC = 3.6 V to 34 V
Frequency temperature
characteristics 1
fOUT = 200 kHz,
Ta = −30°C to +25°C
±3
±3
%
%
Frequency temperature
characteristics 2
fOUT = 200 kHz,
Ta = 25°C to 85°C
Note)
At VCC = 12 V, RT = 15 kΩ, CT = 15 pF, unless otherwise specified.
3
AN8013SH
Voltage Regulators
■ Electrical Characteristics at Ta = 25°C (continued)
Parameter
Short-circuit protection circuit block
Input threshold voltage
Input standby voltage
Input latch voltage
Symbol
Conditions
Min
Typ Max Unit
VTHPC
VSTBY
VIN
0.70 0.75 0.80
V
V
120
120
−1.6 −1.3 − 1.0
1.90
mV
µA
V
Charge current
ICHG
VSCP = 0 V
Comparator threshold voltage
Overcurrent Protection Block
Input threshold voltage
Delay time
VTHL
VCLM
tDLY
VCC −120 VCC −100 VCC −80 mV
200
ns
Whole device
Total consumption current 1
Total consumption current 2
ICC
RT = 15 kΩ
2.4
3.5
mA
mA
ICC2
RT = 5.1 kΩ, CT = 150 pF
3.4
Note)
At VCC = 12 V, RT = 15 kΩ, CT = 15 pF, unless otherwise specified.
■ Terminal Equivalent Circuits
Pin No.
Pin
I/O
Function
Internal equivalent circuit
1
CLM
I
Detects the overcurrent state in switching
transistor.
1
VCC
0.1 V
Insert a resistor with a low resistance between
this pin and VCC to detect overcurrent states.
When this pin falls to a level 100 mV or more
lower than VCC, the PWM output is turned off
for that period thus narrowing the width of
the on period.
CLM
comp.
50 µA
50 µA
(This implements a pulse-by-pulse
overcurrent protection technique.)
VREF
2
RT
I
Connection for the timing resistor that deter-
mines the oscillator frequency.
Use a resistor in the range 5.1 kΩ to 15 kΩ.
Thus the pin voltage will be about 0.59 V.
OSC PWM
100 Ω
S.C.P. DTC
RT (V ≈ 0.59 V)
2
3
CT
O
Connection for the timing capacitor that
determines the oscillator frequency.
VREF
To PWM input
IO
Use a capacitor in the range 100 to 1 800 pF.
See the "Application Notes, [2] and [3]"
sections later in this document for details on
setting the frequency. Use an oscillator
frequency in the range 20 kHz to 500 kHz.
OSC
comp.
3
2IO
4
Voltage Regulators
AN8013SH
■ Terminal Equivalent Circuits (continued)
Pin No.
Pin
I/O
Function
Internal equivalent circuit
4
S.C.P.
O
Connection for the capacitor that determines
the time constant for soft start and the timer
latch short-circuit protection circuit.
Use a capacitor with a value of 1 000 pF or
higher.
VREF
ICHG
Latch
S
The charge current ICHG is determined by the
timing resistor RT, and sample-to-sample and
temperature variations can be suppressed.
When RT is 15 kΩ, the current will be about
−1.3 µA.
Q
U.V.L.O.
0.75 V
R
4
VRT
RT
1
ICHG
=
×
[A]
30
5
DTC
I
Connection for the resistor and capacitor that
determine the PWM output dead-time and the
soft start period.
VREF
PWM
The input current IDTC is determined by the
timing resistor RT, and sample-to-sample and
temperature variations can be suppressed.
When RT is 15 kΩ, the current will be about
−11 µA.
IDTC
U.V.L.O.
CT
5
VRT
RT
1
ICHG
=
×
[A]
3.6
6
7
8
FB
O
Error amplifier output
VREF
120 µA
CT
A source current is about −120 mA and a sink
current is about 8 mA.
PWM
Correct the gain and the phase frequency
characteristics by inserting a resistor and a
capacitor between this pin and IN−pin.
8 mA
6
VREF
IN−
I
Error amplifier inverting input
For common-mode input, use in the range
− 0.1 V to +0.8 V.
0.75 V
7
GND
Ground
8
5
AN8013SH
Voltage Regulators
■ Terminal Equivalent Circuits (continued)
Pin No.
Pin
I/O
Function
Internal equivalent circuit
9
Out
O
Open-collector (darlington) output
The absolute maximum rating for the output
current is 100 mA.
VREF
9
Use with a constant output current under 50
mA.
10
VCC
Power supply connection
10
Provide the operating supply voltage in
the range 3.6 V to 34 V.
■ Application Notes
[1] Main characteristics
Error amplifier input threshold voltage temperature
characteristics
Maximum duty ratio temperature characteristics
0.760
60
VCC = 12 V
VCC = 12 V
CT = 200 pF
RT = 15 kΩ
Voltage follower
0.758
58
56
54
52
0.756
0.754
0.752
0.750
−40 −20
0
20
40
60
80
100
−40 −20
0
20
40
60
80
100
Ambient temperature Ta (°C)
Ambient temperature Ta (°C)
Oscillator frequency temperature characteristics
Timing capacitance Oscillator frequency
215
1M
VCC = 12 V
CT = 200 pF
RT = 15 kΩ
VCC = 12 V
Ta = 25°C
210
205
200
195
RT = 5.1 kΩ
100k
RT = 15 kΩ
10k
−40 −20
0
20
40
60
80
100
100
1 000
10 000
Ambient temperature Ta (°C)
Timing capacitance CT (pF)
6
Voltage Regulators
AN8013SH
■ Application Notes (continued)
[1] Main characteristics (continued)
Input threshold voltage line regulation
Total consumption current line regulation
0.765
4.0
3.5
3.0
2.5
2.0
Ta = 25°C
Ta = 25°C
0.760
0.755
0.750
0.745
RT = 5.1 kΩ
RT = 15 kΩ
0
5
10
15
20
25
30
35
0
5
10
15
20
25
30
35
Supply voltage VCC (V)
Supply voltage VCC (V)
Timing resistance
Total consumption current
Timing resistance
Output saturation voltage
3.5
0.85
VCC = 12 V
VCC = 12 V
IO = 50 mA
Ta = 25°C
T
a = 25°C
0.84
0.83
0.82
0.81
0.80
3.0
2.5
2.0
4
8
12
16
20
4
8
12
16
20
Timing resistance RT (kΩ)
Timing resistance RT (kΩ)
7
AN8013SH
Voltage Regulators
■ Application Notes
[2] Function descriptions
1. Reference voltage block
The reference voltage block is based on a band gap circuit, and outputs a temperature corrected reference
voltage of 2.5 V. This reference voltage is stabilized once the supply voltage exceeds 3.6 V, and is used as the
power supply for the IC itself.
2. Triangular wave generator
This circuit generates a triangular wave with a peak of about 1.45 V and a trough of about 0.35 V using a timing
capacitor connected to the CT pin (pin 3) and a timing resistor connected to the RT pin (pin 2) respectively. The
oscillator frequency can be set to arbitrary value by selecting appropriate values for the external capacitor and
resistor, CT and RT. The triangular wave signal is provided to the inverting input the PWM comparator internally
to the IC.
3. Error amplifier
FB
This circuit is an PNP-transistor input error ampli-
fier that detects and amplifies the DC-DC converter
Internal 2.5 V
output voltage, and inputs that signal to a PWM com-
reference voltage
6
VOUT
parator.
PWM
comparator
input
R3
R1
A 0.75 V level is created by resistors dividing the
internal reference voltage. This level is applied to the
noninverting input.
Arbitrary gain and phase compensation can be set
up by inserting a resistor and capacitor in series
between the error amplifier output pin (pin 6) and the
inverting input pin (pin 7).
Error amp.
0.75 V
IN−
7
R4
R2
Figure 1. Connection method of error amplifier
The output voltage VOUT is given by the following
formula by connecting a resistor divider to the output
as shown in figure 1.
R1 + R2
V
OUT = 0.75 ×
R2
4. Timer latch short-circuit protection circuit
This circuit protects the external main switching element, flywheel diode, choke coil, and other components
against degradation or destruction if an excessive load or a short circuit of the power supply output continues for
longer than a certain fixed period.
The timer latch short-circuit protection circuit detects the output of the error amplifier. If the DC-DC converter
output voltage drops and an error amplifier output level exceeds 1.90 V, this circuit outputs a low level and the
timer circuit starts. This starts charging the external protection circuit delay time capacitor.
If the error amplifier output does not return to the normal voltage range before that capacitor reaches 0.75 V,
the latch circuit latches, the output drive transistors are turned off, and the dead-time is set to 100%.
5. Low input voltage malfunction prevention circuit (U.V.L.O.)
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, this circuit cuts off the output drive transistor until the
reference voltage reaches 3.1 V. It also sets the dead-time to 100%, and at the same time holds the S.C.P. pin (pin
4) at the low level. During the fall time of the power supply voltage, it has hysteresis width of 200 mV and operates
2.9 V or less.
8
Voltage Regulators
AN8013SH
■ Application Notes (continued)
[2] Function descriptions (continued)
6. PWM comparator
The PWM comparator controls the output pulse on-period according to the input voltage. The output transistor
is turned on during periods when the level of the CT pin (pin 3) triangular wave is lower than both of the error
amplifier output (pin 6) and the DTC pin (pin 5) voltage.
The dead-time is set by adding a resistor between the DTC pin and ground.
Additionally, the AN8013SH can provide soft start operation in which the output pulse on-period is gradually
lengthened according to an RC time constant when power is first applied by adding a capacitor in parallel with the
resistor RDTC
.
7. Overcurrent protection block
Destruction of the main switching device, the flywheel diode, and the choke coil, which are easily damaged
by overcurrents, is prevented by limiting the maximum current that flows in the switching device. This is imple-
mented using the fact that power supply output overcurrents are proportional to the current flowing in the main
switching device (a bipolar transistor).
The AN8013SH detects the current by connecting a resistor with a low resistance between the main switching
device and the VCC pin and monitoring the voltage drop across this resistor at the CLM pin (pin 1). When the main
switching device (a bipolar transistor) is on and the CLM pin voltage reaches VCC minus 100 mV, which is the
overcurrent detection threshold voltage, the AN8013SH shuts off the output transistor, thus controlling the main
switching device so that currents in excess of the limit cannot occur. While this control operation is repeated at
each period, once an overcurrent is detected the output transistor is turned off for the remainder of that period and
is not turned on again until the next period. This type of overcurrent protection is called pulse-by-pulse overcurrent
protection.
8. Output block
The output drive transistor is of open-collector type output in which transistors are darlington-connected with
a grounded common emitter. The breakdown voltage of collector output terminal (pin 5) is 34 V and it is possible
to obtain up to 100 mA output current.
5
On at the next period
3
Output off
1.4 V
0.4 V
Triangle wave (CT)
Error amplifier output (FB)
High
Low
Output transistor collector
waveform (Out)
VCC
Overcurrent protection input
(CLM)
VCC − 100 mV
1
2
Overcurrent detection
Latch set
TDLY : Delay time
High
Low
Latch circuit set signal
High
Low
Latch circuit reset signal
4
Latch reset
Figure 2. Pulse-by-pulse overcurrent protection operating waveforms
9
AN8013SH
Voltage Regulators
■ Application Notes (continued)
[3] Triangular wave oscillation circuit
1. Setting the oscillator frequency
The waveform of triangular wave oscillation is obtained by charging and discharging of the constant current
IO from the external timing capacitor CT which is connected to CT pin (pin 3). The constant current is set by the
externally attached timing resistor RT.
The peak value of the wave VCTH and the trough value of the wave VCTL are fixed at about 1.45 V typical and
0.35 V typical respectively.
The oscillator frequency fOSC is obtained by the following formula:
1
IO
VCTH = 1.4 V typ.
VCTL = 0.37 V typ.
fOSC
=
=
t1 + t2
2 × CT × (VCTH − VCHL)
VRT
RT
0.59
RT
whereas IO = 1.8 ×
= 1.8 ×
t1
t2
because VCTH − VCTL = 1.1 V
Charging Discharging
1
fOSC
=
[Hz]
2.07 × CT × RT
T
Figure 3. Triangular wave oscillation waveform
The output frequency fOUT is equal to fOSC since it is PWM-controlled.
2. Usage notes
This IC uses the constant current given by the timing resistor RT as the bias current of the triangular wave
generator and the PWM comparator for consumption current reduction. The total consumption current is about 2.4
mA typical when RT is 15 kΩ, and it increases to about 3.4 mA typical when RT is 5.1 kΩ. In order to obtain the
constant output current of 100 mA at the open-collector output, it is necessary to set RT value to 15 kΩ or smaller.
It is possible to use the circuit in the recommended operating range of 20 kHz to 500 kHz of the oscillator
frequency. As the AN8013SH is used at increasingly higher frequencies, the amount of overshoot and undershoot
due to the operation delay in the triangular wave oscillator comparator increases, and discrepancies between the
values calculated as described previously and the actual values may occur. See the timing capacitance - oscillator
frequency relationship in the "Application Notes, [1] Main characteristics" section of this document.
Note that this IC can not be used as an IC for slave when the several ICs are operated in parallel synchronous
mode.
[4] Setting the dead-time (maximum duty)
The dead-time is set, as shown in figure 4, by setting the DTC pin (pin 5) voltage, VDTC. Since the DTC pin
has a constant current output set with the resistor RT, VDTC is adjusted by adding the external resistor RDTC. The
output duty, Du, and the DTC pin voltage, VDTC, are expressed by the following formulas. For an oscillator
frequency of 200 kHz, the output duty will be 0% at VDTC = 0.45 V, and 100% at VDTC = 1.45 V. However, care
is required here, since the amount of overshoot and undershoot in the triangular wave peak (VCTH) and minimum
(VCTL) values depends on the oscillator frequency.
10
Voltage Regulators
AN8013SH
■ Application Notes (continued)
[4] Setting the dead-time (maximum duty) (continued)
CT waveform
VCTH
VREF
IDTC
DTC
waveform
VDTC
VCTL
VRT
RT
1
3.6
IDTC
=
×
[A]
PWM
CT
FB
tOFF
Off
tON
On
DTC
RDTC
OUT
waveform
Off
CDTC
tON
Du
=
=
× 100 [%]
× 100 [%]
tON + tOFF
VCTH −VDTC
VCTH −VCTL
Example: When fOSC = 200 kHz (R = 15 kΩ, C = 150 pF)
T
T
VCTH ≈ 1.45 V (typ.)
VRT ≈ 0.59 V (typ.)
VDTC = IDTC × RDTC
VCTL ≈ 0.35 V (typ.)
IDTC ≈ 11 µA (typ.)
RDTC
1
×
= VRT
×
[V]
RT
3.6
Figure 4. Setting the dead-time
Adding the external resistor RDTC and the capacitor CDTC in parallel implements a soft start function that causes
the output pulse on width to increase gradually when the power supply is started. Use of this function can prevent
DC-DC converter output overshoot.
[5] Setting the time constant of the timer latch short-circuit protection circuit
The structural block diagram of protection latch circuit is shown in figure 5. The comparator for short-circuit
protection compares the output of error amplifier VFB with the reference voltage of 1.90 V all the time.
When the load conditions of DC-DC converter output are stabilized, there is no fluctuation of error amplifier output,
and the short-circuit protection comparator also keeps the balance. At this moment, the output transistor Q1 is in the
conductive state and the S.C.P. pin is hold to about 30 mV through the clamp circuit.
When the load conditions suddenly change, and high-level signal (1.90 V or higher) is input from the error amplifier
to the non-inverted input of the short-circuit protection comparator, the short-circuit protection comparator outputs
the low-level signal. Since this signal cuts off the output transistor Q1, the S.C.P. pin voltage VPE is released, and the
externally connected capacitor CS starts charging according to the following equation :
When the external capacitor CS has been charged up to about 0.75 V, it sets the latch circuit, cuts off the output drive
transistor by enabling the low input voltage malfunction prevention circuit, and sets the dead-time at 100%.
tPE
VPE = VSTBY + ICHG
×
[V]
CS
tPE
0.75 V = 0.03 V + ICHG
×
CS
tPE
CS = ICHG
×
[F]
0.72
11
AN8013SH
Voltage Regulators
■ Application Notes (continued)
[5] Setting the time constant of the timer latch short-circuit protection circuit (continued)
ICHG is the constant current determined by the oscillation timing resistor RT, and its dispersion and fluctuation with
temperature are small. ICHO is expressed in the following equation :
VRT
RT
1
ICHG
=
×
[A]
30
VRT is about 0.5 V and ICHO becomes about 1.1 µA at RT = 15 kΩ.
Once the low input voltage malfunction prevention circuit is enabled, the S.C.P. pin voltage is discharged to about
30 mV but the latch circuit is not reset unless the power is turned off.
VREF
ICHG
PWM comparator input
FB 6
0.75 V
Error amp.
0.75 V
Output cut-off
S.C.P. comp.
1.90 V
R
S
R
IN−
7
U.V.L.O.
Latch
Q1
Q2
4
S.C.P.
CS
Figure 5. Short-circuit protection circuit
When the power supply is started, the output appears to be shorted. The error amplifier output goes to the high
state, the S.C.P. pin voltage, VPE, is released, and charging starts. The external capacitor value must be set so that DC-
DC converter voltage output starts before the latch circuit in the later stage is set. If the soft start function is used,
special care is required to assure that the start time does not become excessive.
12
Voltage Regulators
AN8013SH
■ Application Notes (continued)
[6] Timing chart
VCC (0 V→3.6 V)
rise time
tr (VCC) ≥ 10 [µs]
Supply voltage (VCC
)
3.6 V
2.5 V
3.1 V typ.
Lock-out
release
Internal reference voltage
Error amplifier output (FB)
1.90 V
1.40 V
DTC pin voltage
Triangular wave (CT)
Power supply on
0.40 V
0.03 V
High
S.C.P. pin voltage
Output transistor
collector waveform
(Out)
Low
Soft start operation
Maximum duty
Figure 6. PWM comparator operation waveform
2.5 V
Internal reference voltage
Short-circuit protection input threshold level
Comparator threshold level
1.90 V
1.40 V
0.40 V
Dead-time voltage (VDT
)
Error amplifier output (FB)
Triangular wave(CT)
High
Output transistor collector waveform
(Out)
Low
0.75 V
S.C.P. pin voltage
0.03 V
High
Short-circuit protection comparator
output
tPE
Low
Figure 7. Short-circuit protection operation waveform
13
AN8013SH
Voltage Regulators
■ Application Circuit Examples
1. Step-down circuit
In
Out
+5 V
62 kΩ
11 kΩ
SBD
100 kΩ
0.001µF
f = 200 kHz
Dumax = 80%
R
DTC = 110 kΩ
15 kΩ
150 pF
0.01 µF
0.033 µF
110 kΩ
2. Step-up circuit
SBD
In
Out
+12 V
150 kΩ
10 kΩ
100 kΩ
0.001 µF
f = 200 kHz
Dumax = 80%
RDTC = 110 kΩ
15 kΩ
150 pF
0.01 µF
0.033 µF
110 kΩ
14
Voltage Regulators
AN8013SH
■ Application Circuit Examples (continued)
3. On/off circuit example
1) Cutting the power supply line
Q3
Q1
In
VO
SBD
ICC
C10
Q2
On/off
Standby current ≈ 0 µA
2) Cutting the IC VCC line
Q3
SBD
In
VO
Q1
ICC
C10
Q2
On/off
Standby current ≈ 0 µA
4. Usage
Since this IC does not include an on/off circuit, an external circuit must be added to implement a standby function.
If a switch (Q1) is inserted in the power supply line as shown in on/off circuit example 1, the standby current can
be held to 0. In this circuit, a transistor essentially equivalent to the one used for the main switching device (Q3) is
required.
If a switch (Q1) is inserted between the power supply line and the IC VCC pin (pin 10) as shown in on/off circuit
example 2, the size of the switching device (Q1) can be reduced. However, the sample-to-sample variations in the Q1
saturation voltage will result in sample-to-sample variations in the overcurrent protection threshold level.
5. Usage Notes
If an external on/off circuit is added, the VCC rise time may become excessively steep and the IC internal latch circuit
may be set at that time, causing problems at power supply startup. To avoid such problems, set the value of C10 so that
the VCC (pin 10) rise time is at least 10 µs.
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