Voltage Regulators
AN8014S
Step-down, step-up, or inverting DC-DC converter control IC
■ Overview
Unit: mm
The AN8014S is a single-channel PWM DC-DC
converter control IC.
This IC can provide any one output type from
among step-down, step-up and inverting output.
Allowing n-channel power MOSFET direct driving, the AN8014S is ideal for high-efficiency power
supplies.
10.1±0.3
9
(0.15)
4.2±0.3
6.5±0.3
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1
■ Features
8
1.5±0.2
0.3
0.1±0.1
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• Wide operating supply voltage range (3.6 V to 34 V)
(The voltage is limited within a range between 3.6
V and 17 V if it is connected to a step-down volt1.27
0.4
0.40±0.25
age circuit.)
Seating plane
Seating plane
• Totem pole output circuit: output peak current (±1 A)
SOP016-P-0225A
• On-chip pulse-by-pulse overcurrent detection and
protection circuit
Note) The package of this product will be changed to lead-free type
Threshold voltage VCC − 0.095 V typical
(SOP016-P-0225E). See the new package dimensions section
• On-chip bootstrap circuit (allowing n-channel
later of this datasheet.
MOSFET direct driving.)
• On-chip under-voltage lock-out circuit (U.V.L.O.)
• On-chip on/off function (active-high control input, standby current of maximum 5 µA)
• On-chip timer latch short-circuit protection circuit
• Maximum oscillator frequency (500 kHz)
■ Applications
• DC-DC switching power supply
1
VREF
■ Block Diagram
Triangular
wave OSC
VREF
2.5V
On/off
active-high
16
Pl
OFF
R
Constant
current
source
1 µA
Latch
R
Q
S
S
Boot
strap
15
14
Q
PWM
comp.
13
R
Latch Q
VCC
CB
Out
S
5
Error amp.
7
IN+
IN−
FB
8
S.C.P.
comp.
PGND
SGND
Publication date: April 2002
12
6
11
S.C.P.
CLM
10 µA
Q
U.V.L.O.
10
SDH00004CEB
1
AN8014S
■ Pin Descriptions
Pin No.
Description
Pin No.
Description
1
Internal reference output
9
Not connected
2
Oscillator timing resistor connection
10
Overcurrent protection input
3
Oscillator timing capacitor connection
11
Signal ground
4
Dead-time control
12
Output stage ground
Capacitance connection for short-circuit
13
Totem pole type output
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5
protection delay
14
Bootstrap output
6
Error amplifier noninverting input
15
Supply voltage
7
Error amplifier inverting input
16
On/off control
8
Error amplifier output
Parameter
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■ Absolute Maximum Ratings
Symbol
Rating
Unit
VCC
35
V
ICC
mA
PD
143
mW
Topr
−30 to +85
°C
Tstg
−40 to +125
°C
On/off pin allowable application voltage
VON/OFF
VCC
V
Error amplifier allowable input voltage
VI
− 0.3 to VREF
V
DTC pin allowable application voltage
VDTC
− 0.3 to VREF
V
Out pin allowable application voltage
VOUT
35
V
IO
±100
mA
IO(Peak)
±1 000
mA
CB pin allowable application voltage
VCB
35
V
CB pin constant output current
ICB
−100, 150
mA
CB pin peak output current
ICBP
−500, 1 000
mA
VCLM
VCC
V
Supply voltage
Supply current
Power dissipation
*2
Operating ambient temperature
Storage temperature
*1
*1
Out pin constant output current
Out pin peak output current
CLM pin allowable application voltage
Pl
Note) 1. *1: Except for the operating ambient temperature and storage temperature, all ratings are for Ta = 25°C.
*2: At Ta = 85°C
2. Do not apply external currents or voltages to any pins not specifically mentioned.
For circuit currents, '+' denotes current flowing into the IC, and '−' denotes current flowing out of the IC.
■ Recommended Operating Range
Parameter
Supply voltage
2
Symbol
VCC
Range
Unit
Step-up circuit system
3.6 to 34
Step-down circuit system
3.6 to 17
SDH00004CEB
V
AN8014S
■ Electrical Characteristics at VCC = 12 V, Ta = 25°C
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
2.522
2.6
2.678
V
Reference voltage block
Output voltage
VREF
IREF = −1 mA
Line regulation with input fluctuation
Line
VCC = 3.6 V to 34 V
16
25
mV
Load regulation
Load
IREF = − 0.1 mA to −1 mA
1
10
mV
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U.V.L.O. block
Circuit operation start voltage
VUON
2.8
3.1
3.4
V
Hysteresis width
VHYS
60
140
180
mV
VIO
−6
6
mV
IB
−500
−25
nA
Common-mode input voltage range
VICR
− 0.1
0.8
V
High-level output voltage
VEH
VREF
− 0.3
VREF
− 0.1
V
VEL
0.1
0.3
V
IDTC
Error amplifier block
Input offset voltage
Low-level output voltage
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Input bias current
Dead-time control circuit block
Input current
−15.8 −13.2 −10.6
µA
Low-level input threshold voltage
VDT-L
Duty 0%
0.45
0.65
V
High-level input threshold voltage
VDT-H
Duty 100%
1.2
1.4
V
fOUT
CT = 120 pF, RT = 15 kΩ
196
218
240
kHz
Du
RDTC = 75 kΩ
47
52
57
%
VOL
IO = 70 mA
1.0
1.3
V
VOH
IO = −70 mA
VCB
−2.0
VCB
−1.0
V
VINCB
ICB = −70 mA
VCC
−1.2
VCC
−1.0
VCC
− 0.8
V
Output block
Oscillator frequency
Output duty
Low-level output voltage
High-level output voltage
Bootstrap circuit block
Input standby voltage
Short-circuit protection circuit block
0.70
0.75
0.80
V
VSTBY
30
120
mV
Input latch voltage
VIN
30
120
mV
Charge current
ICHG
VTH
VCLM
Input standby voltage
Pl
VTHPC
Input threshold voltage
−2.76 −2.30 −1.84
µA
V
On/off control block
Threshold voltage
0.8
2.0
Overcurrent protection block
Threshold voltage
SDH00004CEB
VCC VCC VCC
− 0.115 − 0.095 − 0.075
V
3
AN8014S
■ Electrical Characteristics at VCC = 12 V, Ta = 25°C (continued)
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
ICC
5.0
7.0
mA
ICC(SB)
5
µA
Whole device
Total consumption current
Standby current
• Design reference data
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Note) The characteristics listed below are theoretical values based on the IC design and are not guaranteed.
Parameter
Symbol
Conditions
Limit
Unit
Reference voltage block
VTC1
Ta = −30°C to +25°C
±1
%
Output voltage temperature
characteristics 2
VTC2
Ta = 25°C to 85°C
±1
%
Output short-circuit current
Error amplifier block
Output sink current
Output source current
Open-loop gain
Output block
Frequency supply voltage
characteristics
Frequency temperature
characteristics 1
Frequency temperature
characteristics 2
Oscillator block
RT pin voltage
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Output voltage temperature
characteristics 1
IOS
ISINK
VFB = 0.9 V
ISOURCE VFB = 0.9 V
AG
−40
mA
8
mA
−110
µA
70
dB
fdV
fOUT = 200 kHz,
VCC = 3.6 V to 34 V
±3
%
fdT1
fOUT = 200 kHz,
Ta = −30°C to +25°C
±9
%
fdT2
fOUT = 200 kHz,
Ta = 25°C to 85°C
±9
%
VRT
0.4
V
VTHL
1.87
V
200
ns
Short-circuit protection circuit block
Comparator threshold voltage
Delay time
4
Pl
Overcurrent protection circuit block
tDLY
SDH00004CEB
AN8014S
■ Terminal Equivalent Circuits
I/O
1
O
Equivalent circuit
Description
VREF:
Outputs the reference voltage
2.6 V (allowance: 3%)
Incorporating short-circuit protection
against ground.
VCC
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Pin No.
VREF
1
RT:
Connection for the timing resistor which
decides the oscillator frequency. Use a resistor in the range 5.1 kΩ to 30 kΩ. The
pin voltage is approx. 0.4 V.
VREF
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2
DTC
S.C.P.
100 Ω
2 RT(≈ 0.4 V)
3
VREF
To PWM input
IO
CT
3
OSC
comp.
2IO
VREF
PWM comparator
input
Pl
4
DTC 4
CDTC
2
RT
IDTC
RDTC
SDH00004CEB
CT:
Connection for the timing capacitor which
decides the oscillator frequency. Use a capacitor in the range 100 pF to 10 000 pF.
For the oscillator frequency setting, refer
to the "Application Notes, [1] Function
descriptions" section. Use an oscillator frequency in the range 5 kHz to 500 kHz.
DTC:
Connection for a resistor and a capacitor
that set the dead-time and soft start period
of PWM output.
Input current IDTC is decided by the timing
resistor RT which controls sample to sample
variations and temperature variations.
It is approx. −13.2 µA when RT = 15 kΩ.
VRT 1
×
[A]
IDTC =
RT
2
5
AN8014S
■ Terminal Equivalent Circuits (continued)
Pin No.
I/O
5
Equivalent circuit
Description
S.C.P.:
Connection for the capacitor that sets the
soft start period and the timer latch shortcircuit protection circuit time constant.
Use a capacitor with a value of 1 000 pF
or higher.
The charge current ICHG is decided by the
timing resistor RT which controls sample
to sample variations and temperature variations.
It is approx. −2.3 µA when RT = 15 kΩ.
VRT 1
ICHG =
×
[A]
RT 11
VREF
ICHG
Latch
S
R
Q
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U.V.L.O.
output
0.75 V
6
I
7
I
IN+:
Noninverting input to the error amplifier.
Use the common-mode input in the range
− 0.1 V to +0.8 V.
VREF
7
IN−
8
O
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5 S.C.P.
VREF
6
IN+
Source current
8 FB
Sink current
10
I
VCC
0.1 V
10 CLM
CLM
comp.
50 µA
6
FB:
Output from the error amplifier.
The source current is approx. −110 µA and
sink current is approx. 8 mA.
Correct the frequency characteristics of
the gain and the phase by connecting a resistor and a capacitor between this pin
and IN− pin.
N.C.: Not connected.
Pl
9
IN−:
Inverting input to the error amplifier.
Use the common-mode input in the range
− 0.1 V to +0.8 V.
50 µA
SDH00004CEB
CLM:
Detects the overcurrent state in switching
transistor.
Insert a resistor with a low resistance between
this pin and VCC to detect overcurrent states.
When this pin falls to a level 95 mV or
more lower than VCC , the PWM output is
turned off for that period thus narrowing
the width of the on-period.
(This implements a pulse-by-pulse
overcurrent protection technique.)
AN8014S
■ Terminal Equivalent Circuits (continued)
Pin No.
I/O
11
Equivalent circuit
SGND: Signal ground.
11
12
Description
SGND
GND: Output stage ground.
GND
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12
13
O
Out:
Totem pole output.
A constant output current of ±100 mA or a
peak output current of ±1 A can be ob-
VCC
14
O
13 Out
15
I
tained.
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14 CB
CB:
Bootstrap output.
Connect a bootstrap capacitor between
this pin and the n-channel MOSFET sourceside pin of the switching element when
using a step-down voltage circuit.
Short-circuit this pin and the VCC pin when
using a step-up voltage circuit.
VCC: Power supply.
15
VCC
16
I
OFF
16
17 kΩ
Pl
13 kΩ
OFF:
Controls the on/off state.
When the input is high: normal operation
(VOFF > 2.0 V)
When the input is low: standby mode
(VOFF < 0.8 V)
In standby mode, the total current consumption is held to under 10 µA.
■ Application Notes
[1] Function descriptions
1. Reference voltage block
This block is composed of the band gap circuit and outputs the temperature compensated reference voltage (2.6
V) to the VREF pin (pin 1). The reference voltage is stabilized when the supply voltage is 3.6 V or more and used
as the operating power supply in IC. It is possible to take out a load current of up to −1 mA.
SDH00004CEB
7
AN8014S
■ Application Notes (continued)
[1] Function descriptions (continued)
2. The triangular wave generator block (OSC)
The triangular wave which swings from approximately 1.32 V (upper limit value, VOSCH) to approximately 0.44
V (lower limit value, VOSCL) will be generated by connecting a timing capacitor CT and a resistor RT to the CT pin
(pin 3) and RT pin (pin 2) respectively. Oscillator frequency can be freely decided by the value of CT and RT
connected externally. The oscillator frequency fOSC is obtained by the following formula;
VCTH = 1.32 V (typ.)
1
IO
=
t1 + t 2
2 × CT × (VCTH − VCHL)
VRT
0.4
IO = 1.7 ×
= 1.7 ×
RT
RT
Because VCTH − VCTL = 0.88 V
1
fOSC ≈
[Hz]
2.59 × CT × RT
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fOSC =
VCTL = 0.44 V (typ.)
t1
t2
Charging Discharging
Example) An fOSC of approximately 215 kHz will be
obtained if CT is 120 pF and RT is 15 kΩ.
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T
Figure 1. Triangular oscillation waveform
It is possible to use the circuit in the recommended operating range of 5 kHz to 500 kHz of the oscillator
frequency. As the AN8014S 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.
The output source currents of the AN8014S's S.C.P. and DTC pins are determined by the timing resistor RT
which is externally connected to the RT pin. Therefore, note that this IC can not be used as an IC for slave when
the several ICs are operated in parallel synchronous mode.
1
Pl
3. Error amplifier block
Detecting and amplifying DC-DC converter output voltage, the error amplifier with pnp transistor input inputs
the signal to the PWM comparator.
Figure 2 shows the way to connect the error amplifier.
The common-mode input voltage range is − 0.1 V to + 0.8 V, and a voltage obtained by dividing the reference
voltage with built-in resistors is applied to the non-inverting input. Connecting the feedback resistor and the
capacitor between the error amplifier output pin (pin 8) and the inverting input pin (pin 7) allows the arbitrary gain
setting and the phase compensation.
Startup overshooting caused by feedback delays will be suppressed by setting the output source current and
output sink current to as high as 110 µA and 8 mA respectively.
The input voltage VIN+ and VIN− to the error amplifier are obtained from the following formulas.
R4
R2
VIN+ = VREF ×
VIN− = VOUT ×
R3 + R4
R1 + R2
VREF
R3
IN+ 6
Error PWM comparator
amp.
CT
DTC
13
VOUT
IN− 7
R1
R4
8
RNF
FB
R2
CNF
Figure 2. Connection method of error amplifier
8
SDH00004CEB
AN8014S
■ Application Notes (continued)
[1] Function descriptions (continued)
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4. Timer latch short-circuit protection circuit
This circuit protects external main switching devices, flywheel diodes, choke coils and so forth from breakdown
or deterioration when overload or short-circuit of power supply lasts a certain time.
Figure 3 shows the short-circuit protection circuit. The timer latch short-circuit protection circuit detects the
output level of the error amplifier.
If the output voltage of the DC-DC converter is stable, the output of the error amplifier from the FB pin is stable
and the short-circuit protection comparator is well balanced.
In that case, the transistor Q1 is conductive and the S.C.P. pin voltage is approximately 30 mV constantly.
If the load condition changes radically and output signal voltage of the error amplifier (FB) is 1.87 V or
higher, the short-circuit protection comparator outputs low-level voltage. Then, by cutting off the transistor Q1,
the external capacitor CS of S.C.P. pin (pin 5) starts charging with the current ICHG which is obtained from the
following formulas.
tPE
VPE = VSTBY + ICHG ×
[V]
CS
tPE
0.75 V = 0.03 V + ICHG ×
CS
tPE
CS = ICHG ×
[F]
0.72
ICHG is constant current which is determined by the timing resistor RT .
If RT is 15 kΩ, ICHG will be approximately 2.3 µA.
VRT
1
ICHG =
×
[A]
RT
11
When the external capacitor CS is charged up to approximately 0.75 V, the latch circuit will be turned on. Then
the totem-pole output pin will be set to low level and the dead-time will be set to 100%.
When the latch circuit is turned on, the S.C.P. pin will discharge electricity till the voltage on the S.C.P. pin
reduces to approximately 30 mV. The latch circuit cannot be, however, reset until power supply to the AN8014S
is turned off.
VREF
ICHG
Error amp.
IN+ 6
IN− 7
FB 8
S.C.P.
comp.
S
Q
R Q
Latch
Q1
Cut output off
Q2
1.82 V
Pl
5
S.C.P.
CS
Figure 3. Short-circuit protection circuit
5. Low input voltage malfunction prevention circuit (U.V.L.O.)
This circuit protects system from breakdown or deterioration caused by malfunction in control circuit when
supply voltage is dropped during transient time at power on or off.
The low input voltage malfunction prevention circuit detects internal reference voltage which changes in
accordance with the supply voltage level. When the supply voltage is turned on, it sets the dead-time of Out pin
(pin 13) to 100% and keeps the DTC pin (pin 4) and S.C.P. pin (pin 5) low level until the supply voltage reaches
3.1 V. When the supply voltage falls, it will operate even below 2.96 V because of its hysteresis width of 140 mV.
SDH00004CEB
9
AN8014S
■ Application Notes (continued)
[1] Function descriptions (continued)
6. Remote circuit
It is possible to switch on or off the IC control by using an external control signal. When the OFF pin (pin 16)
voltage is lowered to below approximately 0.8 V, the internal reference voltage goes down thereby stopping the
IC control and reducing the circuit current to 5 µA or less. When the OFF pin voltage is increased to approximately
2.0 V or more, the internal reference voltage rises thereby starting the control operation.
CT waveform
DTC
waveform
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7. PWM comparator block
The PWM comparator controls the on-period of output pulse in accordance with the input voltage. While the
triangular wave voltage on the CT pin (pin 3) is lower than both the error amplifier's output voltage on pin 8 and
the voltage on the DTC pin (pin 4), the output on the Out pin (pin 13) will be set to high level. Then the switching
element (n-channel MOSFET) will be turned on.
The dead-time is set by adjusting the voltage VDTC on the DTC pin (pin 5) as shown in figure 4.
The DTC pin has constant current output determined by the resistor RT . Therefore VDTC is adjusted by
connecting the DTC and GND pins through the external resistor RDTC .
When the oscillator frequency fOSC is 200 kHz, the output duty cycle will be 0% at VDTC of 0.44 V typical and
100% at VDTC of 1.32 V typical.
The levels of overshooting and undershooting of the peak value VCTH and the trough value VCTL of the
triangular wave vary with the oscillator frequency.
VCTH
VREF
VDTC
IDTC
CT
FB
VCTL
tOFF
tON
PWM
DTC
Out waveform
Off
On
Off
RDTC
CDTC
Figure 4. Setting the dead-time
Output duty ratio Du and DTC pin voltage VDTC are expressed by the following formulas;
tON
VDTC − VCTL × 1.1
Du =
× 100 [%] =
× 100 [%]
tON − tOFF
(VCTH − VCTL) × 1.1
VRT
1
IDTC =
[A]
×
RT
2
RDTC
1
×
[V]
VDTC = IDTC × RDTC = VRT ×
RT
2
Pl
Example) When fOSC = 215 [kHz] (RT = 15 kΩ, CT = 120 pF) and RDTC = 75 [kΩ]
VCTH is approximately 1.32 V, VCTH is approximately 0.44 V, and VRT is approximately 0.4 V.
Therefore, the following are obtained.
IDTC ≈ 13.3 [µA]
VDTC ≈ 0.99 [V]
Du ≈ 52.3 [%]
There may be an operational delay of the PWM comparator and a difference in peak and trough values of the
triangular wave oscillation. Discrepancies between the values obtained from the above formulas and the actual
values may occur, in which case adjust the values on the mounting substrate.
In starting, if the capacitor CDTC is added in parallel to the external resistor RDTC , and the output pulse width
are gradually widened, the AN8014S will be in soft-start operation. Thus the overshoot at the output of DC-DC
converters can be prevented.
10
SDH00004CEB
AN8014S
■ Application Notes (continued)
[1] Function descriptions (continued)
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8. Overcurrent protection block
Utilizing that the overcurrent of power output is proportional to the current value which flows in the main switch
(power MOSFET), the block regulates the upper limit of the current flowing in the main switch, thus protects the
parts such as main switch device, a flywheel diode and a choke coil from the damage caused by the overcurrent.
The current detection are done by monitoring, at CLM pin (pin 10), the voltage drop in resistor which is placed
between the main switch device and VCC pin.
When the main switch device (power MOSFET) is switched on and the voltage of CLM pin reaches "VCC −
95 mV", threshold level for overcurrent detection, the output drive transistor is cut off so that no more current
flows in the main switch device. This control is repeated at each cycle. When overcurrent is detected once, the
transistor remains off during the same cycle, and is switched on in the next cycle.
Such an overcurrent detection method is called "Pulse-by-pulse overcurrent detection."
(3) Output Off
(5) Turned on in the next cycle
1.32 V
Error amplifier output (FB)
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Triangular wave (CT)
0.44 V
High
Output waveform (Out)
Low
Overcurrent protection input (CLM)
VCC
VCC − 95 mV
(1) Overcurrent detection
tDLY : Delay time
(2) Latch set
Latch circuit set signal
High
Low
High
Latch circuit reset signal
Low
(4) Latch reset
Pl
Figure 5. Waveforms of the pulse-by-pulse overcurrent protection operation
R2 and C1 shown in figure 6 constitute a low-pass
filter to eliminate noise due to parasitic capacitance when
the power MOSFET is turned on.
The cut-off frequency of the filter is obtained from
the following.
fC =
1
[Hz]
2πC1R2
C1
R2
Out
In
R1
V-Out
CLM
Figure 6. CLM noise filter circuit
SDH00004CEB
11
AN8014S
■ Application Notes (continued)
[1] Function descriptions (continued)
9. Bootstrap circuit of output block
If the n-channel MOSFET is used as a switching device for DC-DC converter control of step down method,
a bootstrap circuit is required.
Bootstrap circuit ensures that the gate-source voltage is gate threshold voltage or higher by going up the high
level of the Out pin (pin 13) than VCC voltage when n-channel MOSFET turns on. Figure 7 shows the output of
bootstrap circuit including the external circuit. Figure 8 shows the operating waveform of the bootstrap circuit.
M
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on na
tin nc
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VS
M1
VCC
15
VD1
PWM comparator
CT
DTC
FB
V-Out
VGS
SBD
D1
14 CB
I2
VCB
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Q1
CB
I1
13 Out
Q2
Figure 7. Bootstrap circuit of output block
VCBH
VOH
Turns off
VCC −VDS(ON) [V]
VCC − 0.7 [V]
VCC
CB pin waveform
Turns off
Out pin waveform
0V
M1 source side waveform
VOL
−VF
t1
t2
t3
M1 Off
M1 On
M1 Off
Pl
Figure 8. Bootstrap circuit operating waveform
The following describes the operation of the bootstrap circuit.
1) N-channel MOSFET (M1) off time: t1
While the M1 is turned off, the choke coil is provided with energy from the Schottky barrier diode (SBD)
and the source-side voltage VS of the M1 is fixed to −VF . The bootstrap capacitor CB is charged from the VCC
pin (pin 15) through the AN8014S's internal diode D1.
The voltage VCB on the CB pin (pin 14) is expressed by the following.
VS = −VF
VCB = VCC − VD1
VF : Forward voltage of SBD
VD1 : Forward voltage of D1
Therefore, the charged voltage of bootstrap capacitor CB is expressed by the following.
VCB − VS = VCC − VD1 + VF
12
SDH00004CEB
AN8014S
■ Application Notes (continued)
[1] Function descriptions (continued)
9. Bootstrap circuit of output block (continued)
2) N-channel MOSFET (M1) turn-on time: t2
When the PWM comparator output is inverted, the Out pin (pin 13) output changes into a high level. The
Out pin voltage VO rises toward the CB pin voltage.
VO = VCB − VCE(sat)
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Then the voltage between the gate and source of the M1 is obtained from the following.
VGS = VO + VF
When the Out pin voltage VO is the same as or higher than the gate threshold voltage VTH , the M1 turns
on. Then the M1 source-side voltage rises up to the voltage expressed by the following.
VS = VCC − VDS(ON)
The bootstrap capacitor CB is connected to the source side and CB pin of the M1. Therefore, the CB pin
voltage rises according to the M1 source-side voltage due to capacitor coupling. VCB is expressed by the
following formula.
VCB = VS + VCC − VD1 + VF
= 2 × VCC − VD1 + VDS(ON) + VF
3) N-channel MOSFET (M1) turn-off time: t3
The Out pin voltage turns off after rising to the saturation voltage of the AN8014S's internal transistor Q1.
The M1 source-side voltage drops to −VF . The CB pin voltage drops to VCC − VD1 or below due to capacitive
coupling. Then the M1 will be in the state described in the above 1).
Pl
[2] Bootstrap circuit usage notes
1. Operating voltage range for step-down circuit
Just like what described previously, if a step-down circuit is in DC-DC converter control, the CB pin (pin 14)
voltage will be approximately twice as high as VCC when the n-channel MOSFET as a switching element is turned
on. The allowable voltage applied to the CB pin is 35 V. Therefore the operating supply voltage must be within a
range between 3.6 V and 17 V.
VCB = 2 × VCC − VD1 − VDS (ON) + VF < 35 [V]
35 + VD1 + VDS (ON) − VF
VCC <
[V] < 17 [V]
2
2. Value setting of bootstrap capacitor
The bootstrap capacitor raises the CB pin voltage to VCC or higher due to capacitor coupling to the source side
of the n-channel MOSFET when the n-channel MOSFET is turned on. At that time bootstrap capacitor is discharged by n-channel MOSFET gate-drive-current. If the capacitance of the bootstrap capacitor is too low, an
increase in switching loss will result, which will reduce the efficiency.
Therefore, the capacitance must be large enough in comparison with the gate input capacitance of the nchannel MOSFET. Refer to the following.
CB > Ciss
Determine the best value by testing on the printed circuit board for mounting.
3. CB pin connection for step-up circuit
If a step-up circuit is in DC-DC converter control, no bootstrap circuit is required because the source side of
the n-channel MOSFET is grounded. Therefore, short-circuit the CB pin (pin 14) and the VCC pin (pin 15).
Thus, the operating supply voltage range in the step-up circuit method is between 3.6 V and 34 V.
SDH00004CEB
13
AN8014S
■ Application Notes (continued)
[3] Timing chart
High
OFF pin voltage
Low
3.6 V
Supply voltage (VCC)
Error amplifier output (FB)
M
Di ain
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tin nc
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Internal reference voltage
Power supply
turning on
1.32 V
0.44 V
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.
Out pin waveform
1.87 V
DTC pin voltage
Triangular wave (CT)
S.C.P. pin voltage
2.6 V
Software start operation
0.03 V
High
Low
The maximum duty
Figure 1. PWM comparator operation waveform
Internal reference voltage
Short-circuit protection comparator
(threshold level)
DTC pin voltage
Error amplifier output (FB)
Triangular wave (CT)
Pl
Out pin waveform
2.6 V
1.87 V
1.32 V
0.44 V
High
Low
0.75 V
S.C.P. pin voltage
0.03 V
tPE
Short-circuit protection
comparator output
High
Low
Figure 2. Short-circuit protection operation waveform
14
SDH00004CEB
AN8014S
■ Application Notes (continued)
[3] Timing chart (continued)
Output off
Turned on in the next cycle.
1.32 V
Triangular wave (CT)
0.44 V
Error amplifier output (FB)
High
Out pin waveform
M
Di ain
sc te
on na
tin nc
ue e/
d
Low
VCC
Overcurrent protection input (CLM)
VCC − 95 mV
Overcurrent
detection
tDLY: Delay time
Latch set
High
Latch circuit set signal
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.
Low
High
Latch circuit reset signal
Low
Latch reset
Figure 3. Waveforms of the pulse-by-pulse overcurrent protection operation
[4] PD Ta curves of SOP016-P-0225A
PD T a
600
Glass epoxy printed
circuit board
(50 mm × 50 mm × t0.8 mm)
Rthj−a = 263°C/W
PD = 380 mW (25°C)
400
360
Independent IC
without a heat sink
Rthj−a = 278°C/W
PD = 360 mW (25°C)
300
207
200
Pl
Power dissipation PD (mW)
518
500
143
100
0
0
25
50
75 85
100
125
150
Ambient temperature Ta (°C)
SDH00004CEB
15
AN8014S
■ Application Notes (continued)
[5] Main characteristics
Internal reference voltage temperature characteristics
Oscillator frequency temperature characteristics
225
Oscillator frequency fOUT (kHz)
2.62
220
215
M
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tin nc
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Internal reference voltage VREF (V)
2.63
2.61
−25
0
25
75
100
200
195
−50
125
−25
0
25
50
75
100
125
Ambient temperature Ta (°C)
Ambient temperature Ta (°C)
Output duty ratio DTC pin voltage
Output duty ratio temperature characteristics
100
56
55
Output duty ratio Du (%)
80
Output duty ratio Du (%)
50
205
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2.60
−50
210
60
40
20
0
0.4
54
53
52
51
0.6
0.8
1.0
1.2
50
−50
1.4
DTC pin voltage VDTC (V)
−25
0
25
50
75
100
125
Ambient temperature Ta (°C)
Oscillator frequency Timing capacitance
Output peak current COut
0.6
10 000
0.5
1 000
Output peak current IPeak (A)
Pl
Oscillator frequency fOUT (kHz)
VCC = 12 V
ROUT = 10 Ω
RT = 5.1 kΩ
100
RT = 15 kΩ
10
0.3
0.2
0.1
1
10
100
1 000
0
1 000
10 000
Timing capacitance CT (pF)
16
0.4
5 000
10 000
Value of output connection capacitor COUT (pF)
SDH00004CEB
AN8014S
■ Application Circuit Examples
1. DC-DC converter control (Example of step-down circuit)
In
12 V
3.9 kΩ
0.1 µF
75 kΩ
33 Ω
0.039 µF
47 µF
15 kΩ
120 pF
10 Ω
f = 200 kHz
M
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on na
tin nc
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d
3 CT
4 DTC
1 VREF
9.1 kΩ
100 µF
Out
5V
1 000 pF
2 RT
V1
0.1 Ω
Triangular
wave OSC
VREF
2.5V
OFF 16
Constant
current source
On/off
active-high
R
1 µA
R
10
CLM
Latch
Q S
10 µA
Boot
strap
R
Q
PWM
comp.
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DTC
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so win CT
n g
2 i
FB 8
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de for
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U.V.L.O.
In
14 CB
Q
S
15 VCC
13 Out
Latch Q
S
S.C.P. 5
6
IN+
7
IN−
62 kΩ
Error amp.
S.C.P.
comp.
PGND 12
SGND 11
0.12 µF
100 kΩ
11 kΩ
2. DC-DC converter control (Example of step-up circuit)
VREF
In
1
V1
VREF
2.5V
16
Constant
current source
On/off
active-high
R
1 µA
R
10 µA
Boot
strap
U.V.L.O.
Q
15 VCC
In
14
Q
S
10
CLM
Latch
Q S
Pl
OFF
Triangular
wave OSC
Out
CB
PWM
comp.
13 Out
R
Latch Q
S
6
IN+
7
IN−
Error amp.
FB
8
12
S.C.P.
comp.
PGND
SGND
11
S.C.P. 5
SDH00004CEB
17
AN8014S
■ Application Circuit Examples (continued)
3. DC-DC converter control (Example of polarity-inverting circuit)
Out
RT
CT
DTC
VREF
In
2
3
4
M
Di ain
sc te
on na
tin nc
ue e/
d
1
V1
Triangular
wave OSC
VREF
2.5V
16
On/off
active-high
R
1 µA
R
10
CLM
Latch
Q S
10 µA
15 VCC
Boot
strap
In
14 CB
Q
U.V.L.O.
S
R
Q
PWM
comp.
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FB
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de for
x. ma
ht t
m ion
l
.
OFF
Constant
current source
13 Out
Latch Q
IN+
7
IN−
PGND
11
SGND
6
Error amp.
S.C.P.
comp.
12
S
S.C.P. 5
1
VREF
■ New Package Dimensions (Unit: mm)
• SOP016-P-0225E (Lead-free package)
10.09±0.20
9
Pl
+0.10
0° to 10°
0.50±0.10
Seating plane
0.40+0.10
-0.05
0.10±0.10
1.27
1.50±0.20
8
1
18
0.15-0.05
6.40±0.30
(1.05)
4.30±0.20
16
(0.60)
V1
SDH00004CEB
Seating plane
Request for your special attention and precautions in using the technical information and
semiconductors described in this book
(1) If any of the products or technical information described in this book is to be exported or provided to non-residents, the laws and
regulations of the exporting country, especially, those with regard to security export control, must be observed.
(2) The technical information described in this book is intended only to show the main characteristics and application circuit examples
of the products, and no license is granted under any intellectual property right or other right owned by our company or any other
company. Therefore, no responsibility is assumed by our company as to the infringement upon any such right owned by any other
company which may arise as a result of the use of technical information described in this book.
(3) The products described in this book are intended to be used for standard applications or general electronic equipment (such as office
equipment, communications equipment, measuring instruments and household appliances).
Consult our sales staff in advance for information on the following applications:
– Special applications (such as for airplanes, aerospace, automobiles, traffic control equipment, combustion equipment, life support
systems and safety devices) in which exceptional quality and reliability are required, or if the failure or malfunction of the products may directly jeopardize life or harm the human body.
– Any applications other than the standard applications intended.
(4) The products and product specifications described in this book are subject to change without notice for modification and/or improvement. At the final stage of your design, purchasing, or use of the products, therefore, ask for the most up-to-date Product
Standards in advance to make sure that the latest specifications satisfy your requirements.
(5) When designing your equipment, comply with the range of absolute maximum rating and the guaranteed operating conditions
(operating power supply voltage and operating environment etc.). Especially, please be careful not to exceed the range of absolute
maximum rating on the transient state, such as power-on, power-off and mode-switching. Otherwise, we will not be liable for any
defect which may arise later in your equipment.
Even when the products are used within the guaranteed values, take into the consideration of incidence of break down and failure
mode, possible to occur to semiconductor products. Measures on the systems such as redundant design, arresting the spread of fire
or preventing glitch are recommended in order to prevent physical injury, fire, social damages, for example, by using the products.
(6) Comply with the instructions for use in order to prevent breakdown and characteristics change due to external factors (ESD, EOS,
thermal stress and mechanical stress) at the time of handling, mounting or at customer's process. When using products for which
damp-proof packing is required, satisfy the conditions, such as shelf life and the elapsed time since first opening the packages.
(7) This book may be not reprinted or reproduced whether wholly or partially, without the prior written permission of Matsushita
Electric Industrial Co., Ltd.
