Datasheet AN8014S Datasheet (Panasonic)

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Page 1

Voltage regulators

0.3

(0° to 10°)

(0.15)

10.1±0.3

4.2±0.3

6.5±0.3

16 9

1.27

(0.605)

Seating plane Seating plane

0.40±0.25

0.1±0.1 1.5±0.2

AN8014S

Step-down, step-up, or inverting DC-DC converter control IC

■ Overview

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.

■ Features

• 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 voltage circuit.)

•

Totem pole output circuit: output peak current (±1 A)

• On-chip pulse-by-pulse overcurrent detection and

protection circuit

Threshold voltage V

− 0.095 V typical

• On-chip bootstrap circuit (allowing n-channel 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)

SOP016-P-0225A

Unit: mm

■ Applications

• DC-DC switching power supply

■ Block Diagram

OFF

S.C.P.

2.5V

On/off

active-high

U.V.L.O.

Latch

SGND

REF

Q Q

PGND

DTC

Constant

current

source

1 µA 10 µA

S.C.P. comp.

Latch

RQS

PWM comp.

Triangular wave OSC

Error amp.

Boot strap

CLM

Out

IN+

IN−

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AN8014S Voltage regulators

■ Pin Descriptions

Pin No. Description

1 Internal reference output 2 Oscillator timing resistor connection 3 Oscillator timing capacitor connection 4 Dead-time control 5 Capacitance connection for short-circuit

protection delay 6 Error amplifier noninverting input 7 Error amplifier inverting input 8 Error amplifier output

■ Absolute Maximum Ratings

Parameter Symbol Rating Unit

Supply voltage V Supply current I

Power dissipation Operating ambient temperature Storage temperature

On/off pin allowable application voltage V Error amplifier allowable input voltage V DTC pin allowable application voltage V Out pin allowable application voltage V Out pin constant output current I Out pin peak output current I CB pin allowable application voltage V CB pin constant output current I CB pin peak output current I CLM pin allowable application voltage V

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.

opr

stg

ON/OFF

DTC

OUT

O(Peak)

CBP

CLM

Pin No. Description

9 Not connected 10 Overcurrent protection input 11 Signal ground 12 Output stage ground 13 Totem pole type output 14 Bootstrap output 15 Supply voltage 16 On/off control

35 V  mA

143 mW

−30 to +85 °C

−40 to +125 °C

− 0.3 to V

REF

35 V

±100 mA

±1 000 mA

35 V

−100, 150 mA

−500, 1 000 mA

V V V

■ Recommended Operating Range

Parameter Symbol Range Unit

Supply voltage V

Step-up circuit system 3.6 to 34 V Step-down circuit system 3.6 to 17

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Voltage regulators AN8014S

■ Electrical Characteristics at V

= 12 V, Ta = 25°C

Parameter Symbol Conditions Min Typ Max Unit

Reference voltage block

Output voltage V Line regulation with input fluctuation

REFIREF

Line VCC = 3.6 V to 34 V  16 25 mV

Load regulation Load I

U.V.L.O. block

Circuit operation start voltage V Hysteresis width V

UON

HYS

Error amplifier block

Input offset voltage V Input bias current I Common-mode input voltage range V High-level output voltage V

Low-level output voltage V

ICR

Dead-time control circuit block

Input current I Low-level input threshold voltage V High-level input threshold voltage V

DTC

DT-L

DT-H

Output block

Oscillator frequency f

OUT

Output duty Du R Low-level output voltage V High-level output voltage V

OLIO

OHIO

Bootstrap circuit block

Input standby voltage V

INCBICB

Short-circuit protection circuit block

Input threshold voltage V Input standby voltage V Input latch voltage V Charge current I

THPC

STBY

CHG

On/off control block

Threshold voltage V

Overcurrent protection block

Threshold voltage V

CLM

= −1 mA 2.522 2.6 2.678 V

= − 0.1 mA to −1 mA  110mV

REF

 2.8 3.1 3.4 V  60 140 180 mV

−6  6mV −500 −25  nA − 0.1  0.8 V  V

REFVREF

 V

− 0.3 − 0.1

0.1 0.3 V

−15.8 −13.2 −10.6 µA

Duty 0%  0.45 0.65 V Duty 100% 1.2 1.4  V

CT = 120 pF, RT = 15 kΩ 196 218 240 kHz

= 75 kΩ 47 52 57 %

DTC

= 70 mA  1.0 1.3 V = −70 mA V

 V

−2.0 −1.0

= −70 mA V

CCVCC

−1.2 −1.0 − 0.8

 0.70 0.75 0.80 V 30 120 mV 30 120 mV −2.76 −2.30 −1.84 µA

 0.8  2.0 V

 V

CCVCC

− 0.115− 0.095− 0.075

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AN8014S Voltage regulators

■ Electrical Characteristics at V

= 12 V, Ta = 25°C (continued)

Parameter Symbol Conditions Min Typ Max Unit

Whole device

Total consumption current I Standby current I

CC(SB)

5.0 7.0 mA 5 µA

• Design reference data

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

Output voltage temperature V

Ta = −30°C to +25°C ±1%

TC1

characteristics 1 Output voltage temperature V

Ta = 25°C to 85°C ±1%

TC2

characteristics 2 Output short-circuit current I

−40 mA

Error amplifier block

Output sink current I Output source current I

SOURCEVFB

Open-loop gain A

SINKVFB

= 0.9 V 8 mA = 0.9 V −110 µA

 70 dB

Output block

Frequency supply voltage f

= 200 kHz, ±3%

OUT

characteristics VCC = 3.6 V to 34 V Frequency temperature f

dT1

= 200 kHz, ±9%

OUT

characteristics 1 Ta = −30°C to +25°C

Frequency temperature f

dT2

= 200 kHz, ±9%

OUT

characteristics 2 Ta = 25°C to 85°C

Oscillator block

RT pin voltage V

 0.4 V

Short-circuit protection circuit block

Comparator threshold voltage V

THL

 1.87 V

Overcurrent protection circuit block

Delay time t

DLY

 200 ns

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Voltage regulators AN8014S

■ Terminal Equivalent Circuits

Pin No. I / O Equivalent circuit Description

1O V

REF

Outputs the reference voltage

Incorporating short-circuit protection against ground.

REF

2  RT:

REF

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.

DTC S.C.P.

100 Ω

RT(≈ 0.4 V)

3  CT:

REF

To PWM input

Connection for the timing capacitor which decides the oscillator frequency. Use a ca-

pacitor in the range 100 pF to 10 000 pF.

OSC comp.

For the oscillator frequency setting, refer

to the "Application Notes, [1] Function descriptions" section. Use an oscillator fre-

quency in the range 5 kHz to 500 kHz.

2.6 V (allowance: 3%)

4  DTC:

REF

PWM comparator

input

Connection for a resistor and a capacitor that set the dead-time and soft start period of PWM output. Input current I

DTC

resistor R variations and temperature variations. It is approx. −13.2 µA when RT = 15 kΩ.

DTC

is decided by the timing

DTC

which controls sample to sample

× 1

RT2

[A]

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AN8014S Voltage regulators

■ Terminal Equivalent Circuits (continued)

Pin No. I / O Equivalent circuit Description

5  S.C.P.:

REF

CHG

Latch

U.V.L.O.

output

6I IN+:

REF

0.75 V

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 I timing resistor R

is decided by the

CHG

which controls sample

to sample variations and temperature variations. It is approx. −2.3 µA when R

VRT × 1

CHG

RT11

[A]

= 15 kΩ.

Noninverting input to the error amplifier. Use the common-mode input in the range

− 0.1 V to +0.8 V.

7I IN−:

Inverting input to the error amplifier. Use the common-mode input in the range

− 0.1 V to +0.8 V.

7 6

IN− IN+

8 O FB:

REF

Source current

Output from the error amplifier. The source current is approx. −110 µA and sink current is approx. 8 mA. Correct the frequency characteristics of

Sink current

the gain and the phase by connecting a resistor and a capacitor between this pin and IN− pin.

9 N.C.: Not connected.

10 I CLM:

0.1 V

CLM

Detects the overcurrent state in switching transistor. Insert a resistor with a low resistance between this pin and VCC to detect overcurrent states.

CLM comp.

When this pin falls to a level 95 mV or more lower than V turned off for that period thus narrowing

50 µA 50 µA

the width of the on-period. (This implements a pulse-by-pulse overcurrent protection technique.)

, the PWM output is

Page 7

Voltage regulators AN8014S

■ Terminal Equivalent Circuits (continued)

Pin No. I / O Equivalent circuit Description

11  SGND: Signal ground.

SGND

12  GND: Output stage ground.

GND

13 O Out:

Totem pole output.

14 O CB:

Out

15 I V

A constant output current of ±100 mA or a peak output current of ±1 A can be ob-

tained.

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 V

pin when

using a step-up voltage circuit.

: Power supply.

16 I

OFF

Controls the on/off state.

OFF

17 kΩ

13 kΩ

When the input is high: normal operation (V

> 2.0 V)

OFF

When the input is low: standby mode (V

< 0.8 V)

OFF

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 V as the operating power supply in IC. It is possible to take out a load current of up to −1 mA.

pin (pin 1). The reference voltage is stabilized when the supply voltage is 3.6 V or more and used

REF

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AN8014S Voltage regulators

■ 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, V

V (lower limit value, V (pin 3) and R

pin (pin 2) respectively. Oscillator frequency can be freely decided by the value of CT and R

connected externally. The oscillator frequency f

≈

t1 + t

CTH

2.59 × C

of approximately 215 kHz will be

OSC

= 1.7 ×

Because V f

OSC

Example) An f

obtained if C

) will be generated by connecting a timing capacitor CT and a resistor RT to the CT pin

OSCL

is obtained by the following formula;

OSC

0.4 R

[Hz]

O CTH

− V

CHL

)

Charging Discharging

Figure 1. Triangular oscillation waveform

2 × CT × (V

= 1.7 ×

− V

= 0.88 V

CTL

× R

is 120 pF and RT is 15 kΩ.

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 R 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.

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 V

= V

REF

IN+

R3 + R

and V

to the error amplifier are obtained from the following formulas.

IN−

= V

IN−

OUT

R1 + R

) to approximately 0.44

OSCH

= 1.32 V (typ.)

CTH

= 0.44 V (typ.)

CTL

REF

IN+ IN−

6 7

PWM comparator

Error

amp.

DTC

OUT

Figure 2. Connection method of error amplifier

Page 9

Voltage regulators AN8014S

■ Application Notes (continued)

[1] Function descriptions (continued)

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 C following formulas.

= V

STBY

0.75 V = 0.03 V + I

CS = I

CHG

If R

CHG

is constant current which is determined by the timing resistor RT .

is 15 kΩ, I

When the external capacitor C

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.

of S.C.P. pin (pin 5) starts charging with the current I

+ I

0.72

CHG

[V]

[F]

will be approximately 2.3 µA.

[A]

is charged up to approximately 0.75 V, the latch circuit will be turned on. Then

which is obtained from the

CHG

REF

Cut output off

IN+ IN−

6 7

Error amp.

S.C.P. comp.

1.82 V

CHG

S.C.P.

Q Q

Latch

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.

Page 10

AN8014S Voltage regulators

■ 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.

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 V The DTC pin has constant current output determined by the resistor R

connecting the DTC and GND pins through the external resistor R

When the oscillator frequency f

100% at V

of 1.32 V typical.

DTC

is 200 kHz, the output duty cycle will be 0% at V

OSC

The levels of overshooting and undershooting of the peak value V

triangular wave vary with the oscillator frequency.

on the DTC pin (pin 5) as shown in figure 4.

DTC

. Therefore V

DTC

of 0.44 V typical and

DTC

and the trough value V

CTH

is adjusted by

DTC

CTL

of the

CT waveform DTC

waveform

Out waveform

OFF

Off OffOn

CTH

DTC

CTL

REF

DTC

CT FB

PWM

DTC

Figure 4. Setting the dead-time

Output duty ratio Du and DTC pin voltage V

DTC

= I

− t

DTC

Du =

DTC

Example) When f

CTH

× 100 [%] =

OFF

×1[A]

× R

= VRT ×

DTC

= 215 [kHz] (RT = 15 kΩ, CT = 120 pF) and R

OSC

is approximately 1.32 V, V

DTC

DTC CTH

− V

× 1

CTH

are expressed by the following formulas;

DTC

× 1.1

CTL CTL

) × 1.1

× 100 [%]

[V]

= 75 [kΩ]

DTC

is approximately 0.44 V, and VRT is approximately 0.4 V.

Therefore, the following are obtained. I

≈ 13.3 [µA]

DTC

≈ 0.99 [V]

DTC

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 C

is added in parallel to the external resistor R

DTC

, and the output pulse width

DTC

are gradually widened, the AN8014S will be in soft-start operation. Thus the overshoot at the output of DC-DC converters can be prevented.

Page 11

Voltage regulators AN8014S

■ Application Notes (continued)

[1] Function descriptions (continued)

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 V

When the main switch device (power MOSFET) is switched on and the voltage of CLM pin reaches "V

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."

pin.

−

(3) Output Off

Triangular wave (CT)

Error amplifier output (FB)

Output waveform (Out)

Overcurrent protection input (CLM)

(1) Overcurrent detection

(2) Latch set

Latch circuit set signal

Latch circuit reset signal

Figure 5. Waveforms of the pulse-by-pulse overcurrent protection operation

(4) Latch reset

(5) Turned on in the next cycle

: Delay time

DLY

1.32 V

0.44 V

High

Low

High

Low

High

Low

− 95 mV

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.

2πC

1R2

[Hz]

V-Out CLM

Figure 6. CLM noise filter circuit

Out

Page 12

AN8014S Voltage regulators

■ 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 V bootstrap circuit including the external circuit. Figure 8 shows the operating waveform of the bootstrap circuit.

voltage when n-channel MOSFET turns on. Figure 7 shows the output of

PWM comparator

DTC

CB pin waveform

Out pin waveform

0 V

M1 source side waveform

Out

Figure 7. Bootstrap circuit of output block

Turns off

M1 Off

M1 On

SBD

Turns off

M1 Off

V-Out

CBH

CC −VDS(ON)

− 0.7 [V]

−V

[V]

The following describes the operation of the bootstrap circuit.

1) N-channel MOSFET (M1) off time: t While the M1 is turned off, the choke coil is provided with energy from the schottky barrier diode (SBD)

and the source-side voltage V pin (pin 15) through the AN8014S's internal diode D1.

The voltage V

= −V

VCB = VCC − V

on the CB pin (pin 14) is expressed by the following.

VF: Forward voltage of SBD V

: Forward voltage of D1

Therefore, the charged voltage of bootstrap capacitor CB is expressed by the following.

− VS = VCC − VD1 + V

Figure 8. Bootstrap circuit operating waveform

of the M1 is fixed to −VF. The bootstrap capacitor CB is charged from the V

Page 13

Voltage regulators AN8014S

■ Application Notes (continued)

[1] Function descriptions (continued)

9. Bootstrap circuit of output block (continued)

2) N-channel MOSFET (M1) turn-on time: t When the PWM comparator output is inverted, the Out pin (pin 13) output changes into a high level. The

Out pin voltage V

rises toward the CB pin voltage.

VO = VCB − VCE(sat)

Then the voltage between the gate and source of the M1 is obtained from the following.

= VO+V

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.

= VCC − V

DS(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. V following formula.

= VS + VCC − VD1 + V

= 2 × VCC − VD1 + V

DS(ON)

3) N-channel MOSFET (M1) turn-off time: t 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 −V

coupling. Then the M1 will be in the state described in the above 1).

is expressed by the

+ V

. The CB pin voltage drops to VCC − VD1 or below due to capacitive

[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 V

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.

= 2 × VCC − VD1 − V

35 + VD1 + V

DS (ON)

− V

+ VF < 35 [V]

[V] < 17 [V]

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 n-

channel MOSFET. Refer to the following.

> C

iss

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 (pin15).

Thus, the operating supply voltage range in the step-up circuit method is between 3.6 V and 34 V.

Page 14

AN8014S Voltage regulators

■ Application Notes (continued)

[3] Timing chart

High

OFF pin voltage

Supply voltage (VCC)

Internal reference voltage

Error amplifier output (FB)

Low

3.6 V

2.6 V

Power supply

turning on

S.C.P. pin voltage Out pin waveform

Internal reference voltage

Short-circuit protection comparator

(threshold level)

DTC pin voltage

Error amplifier output (FB)

Triangular wave (CT)

Software start operation

DTC pin voltage

Figure 1. PWM comparator operation waveform

1.87 V

1.32 V

0.44 V

0.03 V High

Low

The maximum duty

2.6 V

1.87 V

1.32 V

0.44 V

Out pin waveform

S.C.P. pin voltage

Short-circuit protection

comparator output

Figure 2. Short-circuit protection operation waveform

High

Low

0.75 V

0.03 V

High

Low

Page 15

Voltage regulators AN8014S

■ Application Notes (continued)

[3] Timing chart (continued)

Triangular wave (CT)

Error amplifier output (FB)

Out pin waveform

Overcurrent protection input (CLM)

Overcurrent

detection

Latch circuit set signal

Latch circuit reset signal

Figure 3. Waveforms of the pulse-by-pulse overcurrent protection operation

[4] P

 Ta curves of SOP016-P-0225A

Latch set

Output off

600

Turned on in the next cycle.

Latch reset

 T

DLY

: Delay time

1.32 V

0.44 V

High

Low V

− 95 mV

High

Low

High

Low

518 500

400

(mW)

360

300

207 200

Power dissipation P

143

100

0 25 85 150

Ambient temperature Ta (°C)

Glass epoxy printed circuit board

(50 mm × 50 mm × t0.8 mm) R

= 263°C/W

thj−a

PD = 380 mW (25°C)

Independent IC without a heat sink

= 278°C/W

thj−a

PD = 360 mW (25°C)

50 75 100 125

Page 16

AN8014S Voltage regulators

■ Application Notes (continued)

[5] Main characteristics

Internal reference voltage temperature characteristics Oscillator frequency temperature characteristics

2.63

225

(V)

REF

2.62

2.61

Internal reference voltage V

2.60

−50 100 12550 75025−25

Ambient temperature Ta (°C)

220

(kHz)

215

OUT

210

205

Oscillator frequency f

200

195

−50 100 12550 75025−25

Ambient temperature Ta (°C)

Output duty ratio  DTC pin voltage Output duty ratio temperature characteristics

100

Output duty ratio Du (%)

0.4 1.41.21.00.80.6

DTC pin voltage V

DTC

(V)

−50 100 12550 75025−25

Ambient temperature Ta (°C)

Oscillator frequency  Timing capacitance Output peak current  C

10 000

1 000

(kHz)

OUT

100

RT = 5.1 kΩ

RT = 15 kΩ

Oscillator frequency f

10 100 1 000 10 000

Timing capacitance CT (pF)

0.6

= 12 V

= 10 Ω

OUT

0.5

(A)

0.4

Peak

0.3

0.2

Output peak current I

0.1

1 000 10 000

Value of output connection capacitor C

5 000

Out

OUT

(pF)

Page 17

Voltage regulators AN8014S

■ Application Circuit Examples

1. DC-DC converter control (Example of step-down circuit)

0.12 µF

OFF

S.C.P.

3.9 kΩ

9.1 kΩ

SGND

REF

2.5V

On/off

active-high

U.V.L.O.

Latch

0.1 µF 75 kΩ

Q Q

PGND

1 000 pF

DTC

Constant

current source

1 µA 10 µA

S.C.P. comp.

120 pF

12 V

CT 3

PWM comp.

100 µF

15 kΩ

f = 200 kHz

Triangular wave OSC

Latch

RQS

Error amp.

0.1 Ω

0.039 µF

Boot strap

33 Ω

47 µF

10 Ω

CLM V

Out

IN+

IN−

100 kΩ

62 kΩ

11 kΩ

Out 5 V

2. DC-DC converter control (Example of step-up circuit)

REF

OFF

S.C.P.

REF

2.5V

On/off

active-high

R S

U.V.L.O.

Latch

Q Q

DTC

Constant

current source

1 µA 10 µA

S.C.P. comp.

PWM comp.

In Out

Triangular

wave OSC

Latch

RQS

Boot strap

CLM V

Out

IN+

IN−

Error amp.

SGND

PGND

Page 18

AN8014S Voltage regulators

■ Application Circuit Examples (continued)

3. DC-DC converter control (Example of polarity-inverting circuit)

In Out

REF

DTC

OFF

S.C.P.

Q Q

PGND

Constant

current source

1 µA 10 µA

S.C.P. comp.

PWM comp.

Triangular

wave OSC

Latch

RQS

Error amp.

Boot strap

CLM V

Out

IN+

IN−

REF

2.5V

On/off

active-high

U.V.L.O.

Latch

SGND

Datasheet AN8014S Datasheet (Panasonic)

Specifications and Main Features

Frequently Asked Questions

User Manual