U6084B-MFPG3Y [ATMEL]

PWM Power Control with Automatic Duty-cycle Reduction; PWM功率控制，具有自动占空比降低


型号：	U6084B-MFPG3Y
厂家：	ATMEL
描述：	PWM Power Control with Automatic Duty-cycle Reduction PWM功率控制，具有自动占空比降低驱动器 MOSFET驱动器驱动程序和接口接口集成电路功率控制光电二极管
文件：	总11页 (文件大小：234K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

Features

•

Pulse-width Modulation up to 2-kHz Clock Frequency

Protection Against Short-circuit, Load-dump Overvoltage and Reverse V_S

Duty Cycle 0% to 100% Continuously

Output Stage for Power MOSFET

Interference and Damage Protection According to VDE 0839 and

ISO/TR 7637/1

PWM Power

Control with

Automatic

Duty-cycle

Reduction

•

Charge-pump Noise Suppressed

Ground-wire Breakage Protection

1. Description

The U6084B is a PWM-IC with bipolar technology designed for the control of an

N-channel power MOSFET used as a high-side switch. The IC is ideal for use in the

brightness control (dimming) of lamps such as in dashboard applications. For constant

brightness, the preselected duty cycle can be reduced automatically as a function of

the supply voltage.

U6084B

Figure 1-1. Block Diagram with External Circuit

V_Batt

C₅

V_S

R_sh

Short circuit

latch monitoring

Current monitoring

+ short circuit detection

Charge

pump

RC oscillator

C₃

47 nF

PWM

Logic

C₁

47 kΩ

Control input

Output

Duty cycle

range

0-100%

C₂

Duty cycle

reduction

Voltage

monitoring

Enable/

disable

R₃

150 Ω

Ground

Rev. 4677C–AUTO–09/05

2. Pin Configuration

Figure 2-1. Pinning SO16

GND

16 VS

EN/DIS

OUTPUT

REDUCT

2 VS

SENSE

OSC

11 DELAY

10 NC

LATCH

Table 2-1.

Pin Description

Symbol

GND

EN/DIS

Function

IC ground

Enable/disable

Control input (duty cycle)

Duty cycle reduction

Attenuation

REDUCT

OSC

Oscillator

Not connected

LATCH

Status short-circuit latch

Not connected

DELAY

SENSE

2VS

Short-circuit protection delay

Current sensing

Voltage doubler

Output

OUTPUT

Not connected

Supply voltage V_S

U6084B

4677C–AUTO–09/05

U6084B

3. Functional Description

3.1

Pin1 – GND

3.1.1

Ground-wire Breakage

To protect the FET in case of ground-wire breakage, a 820-kΩresistor between gate and source

is recommended to provide proper switch-off conditions.

3.2

3.3

Pin 2 – Enable/Disable

The dimmer can be switched on or off with pin 2, independently of the set duty cycle.

Table 3-1.

V₂

Pin 2 Function

Function

Disable

Enable

> approximately 0.7V or open

< 0.7V or connected to pin 1

Pin 3 – Control Input

The pulse width is controlled by means of an external potentiometer (47 kΩ). The characteristic

(angle of rotation/duty cycle) is linear. The duty cycle be varied from 0% to 100%. It is possible to

further restrict the duty cycle with resistors R₁and R₂(Figure 7-1 on page 9).

Pin 3 is protected against short-circuit to V_Battand ground GND (V_Batt≤16.5V).

3.4

Pin 4 – Duty Cycle Reduction

With pin 4 connected according to Figure 7-1 on page 9, the set duty cycle is reduced to

_Batt≈ 12.5V. This causes a power reduction in the FET and in the lamps. In addition, the

brightness of the lamps is largely independent of the supply voltage range, V_Batt= 12.5V to 16V.

3.4.1

Output Slope Control

The rise and fall time (t_r, t_f) of the lamp voltage can be limited to reduce radio interference. This

is done with an integrator which controls a power MOSFET as source follower. The slope time is

controlled by an external capacitor C₄and the oscillator current (Figure 7-1 on page 9).

Calculation:

C₄

--------

t_f= t_r= V_Batt

I_osc

With V_Batt= 12V, C₄= 470 pF and I_osc= 40 µA, the controlled slope is

470 pF

------------------

t_f= t_r= 12V ×

× 141 µs

40 µA

3.5

Pin 5 – Attenuation

Capacitor C₄connected to pin 5 damps oscillation tendencies.

4677C–AUTO–09/05

3.6

Pin 6 – Oscillator

The oscillator determines the frequency of the output voltage. This is defined by an external

capacitor, C₂. It is charged with a constant current, I, until the upper switching threshold is

reached. A second current source is then activated which taps a double current, 2 × I, from the

charging current. The capacitor, C₂, is thus discharged by the current, I, until the lower switching

threshold is reached. The second source is then switched off again and the procedure starts

once more.

3.6.1

Example for Oscillator Frequency Calculation

V_T100= V_S× α₁= (V_Batt– I_S× R₃) × α₁

V_T<100= V_S× α₂= (V_Batt– I_S× R₃) × α₂

V_TL= V_S× α₃= (V_Batt– I_S× R₃) × α₃

where

_T100= High switching threshold 100% duty cycle

_T<100= High switching threshold < 100% duty cycle

_TL= Low switching threshold

α₁, α₂and α₃are fixed values

The above mentioned threshold voltages are calculated for the following values given in the

datasheet.

_Batt= 12V, I_S= 4 mA, R₃= 150Ω

α₁= 0.7, α₂= 0.67 and α₃= 0.28

_T100= (12V – 4 mA × 150Ω) × 0.7 ≈ 8V

_T<100= 11.4V × 0.67 = 7.6V

_TL= 11.4V × 0.28 = 3.2V

For a duty cycle of 100%, the oscillator frequency, f, is as follows:

I_osc

f = ----------------------------------------------------------- where C₂= 22 nF and I_osc= 40 µA

2 × (V_T100– V_TL) × C₂

Therefore:

40 µA

f = --------------------------------------------------------------- = 18 9Hz

2 × (8V – 3.2V) × 22 nF

For a duty cycle of less than 100%, the oscillator frequency, f, is as follows:

I_osc

f = ----------------------------------------------------------------------------------------------------------

2 × (V_T<100– V_TL) × C₂+ 4 × V_Batt× C₄

where C₄= 470 pF

40 µA

f = -------------------------------------------------------------------------------------------------------------------------- = 185Hz

2 × (7.6V – 3.2V) × 22 nF + 4 × 12V × 470 pF

A selection of different values of C₂and C₄provides a range of oscillator frequencies from 10Hz

to 2000Hz.

U6084B

4677C–AUTO–09/05

U6084B

3.7

3.8

Pins 7, 8, 10 and 15

Not connected.

Pin 9 – Status Short Circuit Latch

The status of the short-circuit latch can be monitored via pin 9 (open collector output).

Table 3-2.

Pin 9 Function

Pin 9

Function

Short-circuit detected

No short-circuit detected

3.9

Pins 11 and 12 – Short-circuit Protection and Current Sensing

3.9.1

Short-circuit Detection and Time Delay t_d

The lamp current is monitored by means of an external shunt resistor. If the lamp current

exceeds the threshold for the short-circuit detection circuit (V_T2≈ 90 mV), the duty cycle is

switched over to 100% and capacitor C₅is charged by a current source of 20 µA (I_ch– I_dis). The

external FET is switched off after the cut-off threshold (V_T11) is reached. Renewed switching on

of the FET is possible only after a power-on reset. The current source, I_dis, ensures that capaci-

tor C₅is not charged by parasitic currents. Capacitor C₅is discharged by I_disto typically 0.7V.

Time delay, t_d, is as follows:

(V₁₁– 0.7V)

--------------------------------

t_d= C₅×

(I_ch– I_dis

)

With C₅= 330 nF and V_Batt= 12V, we have

(9.8V – 0.7V)

----------------------------------

t_d= 330 nF ×

= 150 ms

20 µA

3.9.2

Current Limitation

The lamp current is limited by a control amplifier that protects the external power transistor. The

voltage drop across an external shunt resistor acts as the measured variable. Current limitation

takes place for a voltage drop of V_T1≈ 100 mV. Owing to the difference V_T– V_T2≈ 10 mV, cur-

rent limitation occurs only when the short-circuit detection circuit has responded.

After a power-on reset, the output is inactive for half an oscillator cycle. During this time, the sup-

ply voltage capacitor can be charged so that current limitation is guaranteed in the event of a

short-circuit when the IC is switched on for the first time.

3.10 Pins 13 and 14 – Charge Pump and Output

Pin 14 (output) is suitable for controlling a power MOSFET. During the active integration phase,

the supply current of the operational amplifier is mainly supplied by capacitor C₃(bootstrapping).

Additionally, a trickle charge is generated by an integrated oscillator (f₁₃≈ 400 kHz) and a volt-

age doubler circuit. This permits a gate voltage supply at a duty cycle of 100%.

4677C–AUTO–09/05

3.11 Pin 16 – Supply Voltage, V_sor V_Batt

3.11.1

Undervoltage Detection

In the event of voltages of approximately V_Batt< 5.0V, the external FET is switched off and the

latch for short-circuit detection is reset.

A hysteresis ensures that the FET is switched on again at approximately V_Batt≥ 5.4V.

3.11.2

Overvoltage Detection

• Stage 1

– If overvoltages of V_Batt> 20V (typically) occur, the external transistor is switched off

and switched on again at V_Batt< 18.5V (hysteresis).

• Stage 2

– If V_Batt> 28.5V (typically), the voltage limitation of the IC is reduced from 26V to 20V.

The gate of the external transistor remains at the potential of the IC ground, thus

producing voltage sharing between the FET and lamps in the event of overvoltage

pulses (for example, load dump). The short-circuit protection is not in operation. At

_Batt< 23V, the overvoltage detection stage 2 is switched off.

U6084B

4677C–AUTO–09/05

U6084B

4. Absolute Maximum Ratings

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating

only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this

specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability

Parameters

Symbol

T_j

Value

150

Unit

°C

Junction temperature

Ambient temperature range

Storage temperature range

T_amb

T_stg

–40 to +110

–55 to +125

°C

5. Thermal Resistance

Parameters

Symbol

Value

Unit

Junction ambient

R_thJA

120

K/W

6. Electrical Characteristics

T_amb= –40 to +110°C, V_Batt= 9V to 16.5V (basic function is guaranteed between 6.0V and 9.0V), reference point ground, unless

otherwise specified (Figure 1-1 on page 1). All other values refer to pin GND (pin 1).

Parameters

Test Conditions

Pin 16

Symbol

I_S

Min.

Typ.

Max.

6.8

Unit

Current consumption

Supply voltage

Overvoltage detection, stage 1

I_S= 10 mA, pin 16

V_Batt

V_S

Stabilized voltage

24.5

27.0

- On

- Off

4.4

4.8

5.0

5.4

5.6

6.0

Battery undervoltage detection

Battery Overvoltage Detection

Stage 1:

V_Batt

Pin 2

- On

- Off

18.3

16.7

20.0

18.5

21.7

20.3

V_Batt

- On

- Off

25.5

19.5

28.5

23.0

32.5

26.5

Stage 2:

V_Batt

V_Z

Stabilized voltage

I_S= 30 mA, pin 16

Pin 12

18.5

20.0

21.5

Short-circuit Protection

Short-circuit current limitation

V_T1= V_S– V₁₂

V_T2= V_S– V₁₂

V_T1

V_T2

100

120

105

Short-circuit detection

V_T1– V_T2

Delay Timer Short-circuit Detection Pin 11

Switched off threshold

Charge current

V_T11= V_S– V₁₁

V_T11

I_ch

9.5

9.8

10.1

µA

Discharge current

Capacitance current

Output Short-circuit Latch

Saturation voltage

Voltage Doubler

Voltage

I_dis

I₅

I₅= I_ch– I_dis

Pin 9

I₉= 100 µA

Pin 13

V_sat

150

400

350

Duty cycle 100%

V₁₃

f₁₃

2 V_S

280

Oscillator frequency

520

kHz

Note:

1. Reference point is battery ground

4677C–AUTO–09/05

6. Electrical Characteristics (Continued)

T_amb= –40 to +110°C, V_Batt= 9V to 16.5V (basic function is guaranteed between 6.0V and 9.0V), reference point ground, unless

otherwise specified (Figure 1-1 on page 1). All other values refer to pin GND (pin 1).

Parameters

Test Conditions

I₁₃= 5 mA

Symbol

V₁₃

Min.

Typ.

27.5

Max.

30.0

Unit

Internal voltage limitation

Gate Output

(Whichever is lower)

Pin 14

V₁₃

(V_S+14

)

(V_S+15

)

(V_S+16)

Low level

V₁₄

0.35

0.70

V₁₃

0.95

V_Batt= 16.5V, T_amb= 110°C,

R₃= 150Ω

Voltage

1.5⁽¹⁾

High level, duty cycle 100%

V₁₄= Low level

V₁₄

I₁₄

1.0

Current

V₁₄= High level, I₁₃

I₁₄

–1.0

Enable/Disable

Current

Pin 2

V₂= 0V

Pin 4

I₂

–20

6.9

–40

7.4

–60

8.0

µA

Duty Cycle Reduction

Z-voltage

I₄= 500 µA

V₄

Oscillator

Frequency

Pin 6

2000

0.72

Threshold cycle

Upper

V_T100

V₁₄= High, α₁= --------------

α₁

0.68

0.7

V_S

V_T<100

V₁₄= Low, α₂= -----------------

V_S

Lower

α₂

α₃

0.65

0.26

0.67

0.28

0.69

0.3

V_TL

α₃= ---------

V_S

Oscillator current

_Batt= 1V

±I_osc

µA

C₄open, C₂= 470 nF,

duty cycle = 50%

Frequency tolerance

6.0

9.9

13.5

Note:

1. Reference point is battery ground

U6084B

4677C–AUTO–09/05

U6084B

7. Application

Figure 7-1. Application

4677C–AUTO–09/05

8. Ordering Information

Extended Type Number

Package

Remarks

U6084B-MFPG3Y

SO16

Taped and reeled, Pb-free

9. Package Information SO16

5.2

4.8

Package SO16

Dimensions in mm

10.0

9.85

3.7

1.4

0.2

0.25

0.10

0.4

3.8

1.27

6.15

5.85

8.89

technical drawings

according to DIN

specifications

10. Revision History

Please note that the following page numbers referred to in this section refer to the specific revision

mentioned, not to this document.

Revision No.

History

• Block Diagram on Page 1 changed

4677B-AUTO-02/03

• New heading rows at Table “Absolute Maximum Ratings” on page 6

added

• Put datasheet in a new template

• Updated text to new style guide

• First page: Pb-free logo added

• Page 9: Ordering Information changed

4677C-AUTO-08/05

U6084B

4677C–AUTO–09/05

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Printed on recycled paper.

4677C–AUTO–09/05

U6084B-MFPG3Y [ATMEL]

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