Diodes AP3512E User Manual

18V, 2A Synchronous DC-DC Buck Converter AP3512E

Preliminary Datasheet

General Description

The AP3512E is a 500kHz fixed frequency, current mode, PWM synchronous buck (step-down) DC-DC converter, capable of driving a 2A load with high efficiency, excellent line and load regulation. The AP3512E exhibits high efficiency at light load. The device integrates N-channel power MOSFET switch with low on-resistance. Current mode control provides fast transient response and cycle-by-cycle current limit.

The AP3512E employs complete protection to ensure system security, including output Over Voltage Protection, input Under Voltage Lock Out, programmable Soft-start, Over Temperature Protection and hiccup mode Short Circuit Protection.

This IC is available in SOIC-8 and PSOP-8 packages.

SOIC-8 PSOP-8

Features

• Input Voltage Range: 4.5V to 18V

• Fixed 500kHz Frequency

• High Efficiency at Light Load

• Output Current: 2A

• Current Mode Control

• Built-in Over Current Protection

• Built-in Thermal Shutdown Function

• Built-in UVLO Function

• Built-in Over Voltage Protection

• Programmable Soft-start

• Hiccup Mode SCP

Applications

• Monitor

• TV

• STB

• Datacom

Figure 1. Package Types of AP3512E

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Preliminary Datasheet

18V, 2A Synchronous DC-DC Buck Converter AP3512E

Pin Configuration

M Package MP Package

(SOIC-8) (PSOP-8)

BS

IN

SW

GND

1

2

3

4

Figure 2. Pin Configuration of AP3512E (Top View)

SS

8

EN

7

COMP

6

5

FB

BS

IN

SW

GND

8

1

2

EP

3

4

SS

EN

7

COMP

6

FB

5

Pin Description

Pin Number Pin Name Function

Bootstrap pin. A bootstrap capacitor is connected between the

1 BS

2 IN

3 SW

4 GND Ground pin

5 FB

6 COMP

7 EN

8 SS

EP Exposed pad. It should be connected to GND in PCB layout

BS pin and SW pin. The voltage across the bootstrap capacitor drives the internal high-side NMOS switch. Supply input pin. A capacitor should be connected between the IN pin and GND pin to keep the DC input voltage constant. Power switch output pin. This pin is connected to the inductor and bootstrap capacitor.

Feedback pin. This pin is connected to an external resistor divider to program the system output voltage. When the FB pin voltage exceeds 1.1V, the over voltage protection is triggered. When the FB pin voltage is below 0.3V, the oscillator frequency is lowered to realize short circuit protection. Compensation pin. This pin is the output of the transconductance error amplifier and the input to the current comparator. This pin is used to compensate the control loop. Connect a series RC network from this pin to GND pin. In some cases, an additional capacitor from this pin to GND pin is required. Enable Input. EN is a digital input that turns the regulator on or off. Drive EN high to turn on the regulator, drive it low to turn off. Pull up with 100kΩ resistor for automatic startup. Soft-start control input pin. SS controls the soft start period. Connect a capacitor from SS to GND to set the soft-start period. A 0.1µF capacitor sets the soft-start period to 15ms. To disable the soft-start feature, leave SS unconnected.

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Preliminary Datasheet

18V, 2A Synchronous DC-DC Buck Converter AP3512E

Functional Block Diagram

Figure 3. Functional Block Diagram of AP3512E

Ordering Information

Circuit Type G1: Green

Package M: SOIC-8 MP: PSOP-8

Package

SOIC-8

Temperature

Range

-40 to 85°C

AP3512E -

Blank: Tube TR: Tape & Reel

Part Number Marking ID

AP3512EM-G1 3512EM-G1 Tube

AP3512EMTR-G1 3512EM-G1 Tape & Reel

Packing

Type

PSOP-8

-40 to 85°C

AP3512EMPTR-G1 3512EMP-G1 Tape & Reel

BCD Semiconductor's Pb-free products, as designated with "G1" suffix in the part number, are RoHS compliant and green.

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Preliminary Datasheet

18V, 2A Synchronous DC-DC Buck Converter AP3512E

Absolute Maximum Ratings (Note 1)

Parameter Symbol Value Unit

IN Pin Voltage VIN -0.3 to 20 V

EN Pin Voltage VEN -0.3 to VIN V

SW Pin Voltage VSW 21 V

BS Pin Voltage VBS -0.3 to VSW+6 V

FB Pin Voltage VFB -0.3 to 6 V

COMP Pin Voltage V

SS Pin Voltage VSS -0.3 to 6 V

Operating Junction Temperature TJ 150 ºC

Storage Temperature T

Lead Temperature (Soldering, 10sec) Thermal Resistance (Junction to Ambient)

ESD (Human Body Model) V

ESD (Machine Model) VMM 200 V

Note 1: Stresses greater than those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under “Recommended Operating Conditions” is not implied. Exposure to “Absolute Maximum Ratings” for extended periods may affect device reliability.

-0.3 to 6 V

COMP

-65 to 150 ºC

STG

260 ºC

T

LEAD

θ

JA

2000 V

HBM

SOIC-8 105 PSOP-8 60

ºC/W

Recommended Operating Conditions

Parameter Symbol Min Max Unit

Input Voltage VIN 4.5 18 V

Operating Ambient Temperature TA -40 85 ºC

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W

Preliminary Datasheet

18V, 2A Synchronous DC-DC Buck Converter AP3512E

Electrical Characteristics

VIN=VEN=12V, V

Parameter Symbol Conditions Min Typ Max Unit

SUPPLY VOLTAGE (IN PIN)

Input Voltage VIN 4.5 18 V

Quiescent Current IQ

Shutdown Supply Current I

UNDER VOLTAGE LOCKOUT

=3.3V, TA=25ºC, unless otherwise specified.

OUT

=1V,

V

FB

=3.3V

V

EN

VEN=0V 0.1 1.0 µA

SHDN

1.2 1.4 mA

Input UVLO Threshold V

Input UVLO Hysteresis V

VIN Rising 3.65 4.0 4.25 V

UVLO

0.2 V

HYS

ENABLE (EN PIN)

EN Shutdown Threshold Voltage

EN Shutdown Threshold Voltage Hysteresis (Note 2)

EN Lockout Threshold Voltage

EN Lockout Hysteresis

1.1 1.5 2 V

350

2.2 2.5 2.7 V

210

mV

VOLTAGE REFERENCE (FB PIN)

Feedback Voltage VFB 0.907 0.925 0.943 V

Feedback Over Voltage Threshold V

1.1 V

FBOV

Feedback Bias Current IFB VFB=1V -0.1 0.1 µA

MOSFET

High-side Switch On-resistance (Note 3) Low-side Switch On-resistance (Note 3)

R

ISW=0.2A&0.7A 100 mΩ

DSONH

ISW=-0.2A&-0.7A 100 mΩ

DSONL

CURRENT LIMIT

High-side Switch Leakage Current

High-side Switch Current Limit I

Low-side Switch Current Limit I

I

LEAKH

4.3 5.6 A

LIMH

LIML

=18V, VEN=0V,

V

IN

=0V

V

S

From drain to source

0.1 10 μA

50 mA

SWITCHING REGULATOR

Oscillator Frequency f

Short Circuit Oscillator Frequency

Dec. 2012 Rev. 1. 1 BCD Semiconductor Manufacturing Limited

410 500 590 kHz

OSC1

180 kHz

f

OSC2

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Preliminary Datasheet

18V, 2A Synchronous DC-DC Buck Converter AP3512E

Electrical Characteristics (Continued)

VIN=VEN=12V, V

Parameter Symbol Conditions Min Typ Max Unit

=3.3V, TA=25ºC, unless otherwise specified.

OUT

Max. Duty Cycle D

Min. Duty Cycle D

VFB=0.85V 90 %

MAX

VFB=1V 0 %

MIN

ERROR AMPLIFIER

Error Amplifier Voltage Gain (Note 2)

400 V/V

A

EA

Error Amplifier Transconductance GEA 800 μA/V

COMP to Current Sense Transconductance

5.2 A/V

G

CS

THERMAL SHUTDOWN

Thermal Shutdown (Note 2) T

Thermal Shutdown Hysteresis (Note 2)

160 ºC

OTSD

30 ºC

T

HYS

SOFT START (SS PIN)

Soft-start Time (Note 2) tSS CSS=0.1μF 15 ms

Soft-start Current 5 μA

Note 2: Not tested, guaranteed by design.

V-V

Note 3: R

DSON

=

SW2SW1

I-I

SW2SW1

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Preliminary Datasheet

18V, 2A Synchronous DC-DC Buck Converter AP3512E

Typical Performance Characteristics

VIN=12V, V

=3.3V, L=4.7µH, TA=25°C, unless otherwise noted.

OUT

100

90

80

70

60

50

Efficiency (%)

40

30

20

10

0.01 0.1 1

VIN=12V

V V

Load Current (A)

=3.3V, L=4.7μH

OUT

=5.0V, L=6.8μH

OUT

1.30

1.25

1.20

1.15

1.10

1.05

1.00

0.95

Quiescent Current (mA)

0.90

0.85

0.80

-50-250 255075100125150

Temperature (oC)

Figure 4. Efficiency vs. Load Current Figure 5. Quiescent Current vs. Temperature

1.2

1.1

1.0

0.9

0.8

Feedback Voltage (V)

0.7

0.6

-50 -25 0 25 50 75 100 125 150

Temperature (oC)

VSW

(10V/div)

V

OUT-AC

(20mV/div)

I (1A/div)

L

Time(1µs/div)

Figure 6. Feedback Voltage vs. Temperature

Figure 7. Output Ripple (I

OUT

=2A)

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Preliminary Datasheet

18V, 2A Synchronous DC-DC Buck Converter AP3512E

Typical Performance Characteristics (Continued)

VIN=12V, V

=3.3V, L=4.7µH, TA=25°C, unless otherwise noted.

OUT

V

OUT-AC

(100mV/div)

I

OUT

(1A/div)

OUT-AC

(100mV/div)

I

OUT

(1A/div)

Figure 8. Load Transient Response (I

Time(100µs/div)

=1A to 2A) Figure 9. Load Transient Response (I

OUT

=0.2A to 2A)

OUT

(10V/div)

V

(2V/div)

I (1A/div)

VIN

OUT

L

VIN

(10V/div)

V

OUT

(2V/div)

I (1A/div)

L

Time(3.20ms/div)

Figure 10. Power On from VIN (I

=2A) Figure 11. Power Off from VIN (I

OUT

=2A)

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Preliminary Datasheet

18V, 2A Synchronous DC-DC Buck Converter AP3512E

Typical Performance Characteristics (Continued)

VIN=12V, V

VEN

(2V/div)

V

OUT

(2V/div)

I (1A/div)

VSS

(1V/div)

V

OUT

(2V/div)

V

(10V/div)

(2A/div)

SW

L

I

L

=3.3V, L=4.7µH, TA=25°C, unless otherwise noted.

OUT

I (1A/div)

Time(3.20ms/div)

Figure 12. Power On from EN (I

Time(64ms/div)

=2A) Figure 13. Power Off from EN (I

OUT

(1V/div)

(10V/div)

I (2A/div)

VEN

(2V/div)

V

OUT

(2V/div)

VSS

V

OUT

(2V/div)

V

L

Time(3.20ms/div)

OUT

SW

L

Time(64ms/div)

Figure 14. Short Circuit Protection (I

=2A) Figure 15. Short Circuit Protection Recovery (I

OUT

=2A)

OUT

=2A)

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Preliminary Datasheet

18V, 2A Synchronous DC-DC Buck Converter AP3512E

Typical Application

Figure 16. Typical Application Circuit of AP3512E

Dec. 2012 Rev. 1. 1 BCD Semiconductor Manufacturing Limited

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Preliminary Datasheet

18V, 2A Synchronous DC-DC Buck Converter AP3512E

Mechanical Dimensions

SOIC-8 Unit: mm(inch)

4.700(0.185)

5.100(0.201)

7

°

1.350(0.053)

1.750(0.069)

0.320(0.013)

°

8

1.000(0.039)

7

°

1.270(0.050) TYP

0.330(0.013)

0.510(0.020)

0.100(0.004)

0.300(0.012)

0.675(0.027)

0.725(0.029)

3.800(0.150)

4.000(0.157)

0.190(0.007)

0.250(0.010)

0.900(0.035)

R0.150(0.006)

D

0

°

8

°

1° 5°

5.800(0.228)

6.200(0.244)

D

1

:

0

2

0.450(0.017)

0.800(0.031)

5

1

.

0

R

°

8

0.200(0.008)

)

6

0

.

0

(

0

Note: Eject hole, oriented hole and mold mark is optional.

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Preliminary Datasheet

18V, 2A Synchronous DC-DC Buck Converter AP3512E

Mechanical Dimensions (Continued)

PSOP-8 Unit: mm(inch)

3.202(0.126)

3.402(0.134)

Dec. 2012 Rev. 1. 1 BCD Semiconductor Manufacturing Limited

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