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AP1538中文资料

Features

General Description

AP1538 consists of step-down switching regulator with PWM control. These devices include a reference voltage source, oscillation circuit, error amplifier, internal PMOS.

? Input voltage : 3.6V to 18V ? Output voltage : 0.8V to V CC ? Output current : up to 3A

AP1538 provides low-ripple power, high efficiency, and excellent transient characteristics. The PWM control circuit is able to vary the duty ratio linearly from 0 up to 99%. This converter also contains an error amplifier circuit as well as a soft-start circuit that prevents overshoot at startup. An enable function, an over current protect function and a short circuit protect function are built inside, and when OCP or SCP happens, the operation frequency will be reduced from 300KHz to 50KHz. Also, an internal compensation block is built in to minimum external component count.

? Duty ratio: 0% to 99% PWM control ? Oscillation frequency: 300KHz typical

? Soft-start like, Current limit and Enable function ? Thermal Shutdown function

? Built-in internal SW P-channel MOS

? SOP-8L and SOP-8L-DEP: Available in “Green” Molding Compound (No Br, Sb)

Lead Free Finish / RoHS Compliant (Note 1)

With the addition of an internal P-channel Power MOS, a coil, capacitors, and a diode connected externally, these ICs can function as step-down switching regulators. They serve as ideal power supply units for portable devices when coupled with the SOP-8L and SOP-8L-DEP mini-packages, providing such outstanding features as low current consumption. Since this converter can accommodate an input voltage up to 18V, it is also suitable for the operation via an AC adapter.

Applications

? PC Motherboard ? LCD Monitor ? Graphic Card

? DVD-Video Player ? Telecom Equipment ? ADSL Modem

? Printer and other Peripheral Equipment ?

Microprocessor core supply

Ordering Information

AP 1538 XXX G - X

Package Packing S : SOP-8L

Lead Free U : Tube

13 : Tape & Reel

G : Green

SDP : SOP-8L-DEP

Tube 13” Tape and Reel

Device Package

Code

Packaging (Note 2)

Quantity Part Number Suffix Quantity Part Number

Suffix

AP1538SG-U S SOP-8L 100 -U NA NA AP1538SG-13 S SOP-8L NA NA 2500/Tape & Reel -13 AP1538SDPG-U SDP SOP-8L-DEP 100 -U NA NA AP1538SDPG-13 SDP SOP-8L-DEP NA NA 2500/Tape & Reel -13

Notes: 1. EU Directive 2002/95/EC (RoHS). All applicable RoHS exemptions applied, see EU Directive 2002/95/EC Annex Notes .

2. Pad layout as shown on Diodes Inc. suggested pad layout document AP02001, which can be found on our website at

https://www.wendangku.net/doc/d06645415.html,/datasheets/ap02001.pdf .

Pin Assignments

(1) SOP-8L (2) SOP-8L-DEP (Dual Exposed Pads)

Output

OCSET

Output

Vss

V CC

( Top View )

Output

OCSET

Output

Vss

V CC

( Top View )

Notes: 3. Exposed pad 1 is connected to VSS and exposed pad 2 is connected to Output. The board layout for exposed pads needs to be considered to avoid short circuit.

Pin Descriptions

Pin Name Pin No. Description

FB 1

Feedback

EN 2

Power-off pin

H: Normal operation

(Step-down operation)

L: Step-down operation stopped

(All circuits deactivated)

OCSET 3 Add an external resistor to set max output current

V CC 4 IC power supply pin

Output 5,

Switch Pin. Connect external inductor/diode here. Minimize trace

area at this pin to reduce EMI

V SS7, 8 GND Pin

Block Diagram

Vcc

Absolute Maximum Ratings

Symbol Parameter

Rating Unit ESD HBM Human Body Model ESD Protection

7 KV ESD MM Machine Model ESD Protection 450

V V CC V CC Pin Voltage V SS - 0.3 to V SS + 20

V FB Feedback Pin Voltage V SS - 0.3 to V CC V V EN EN Pin Voltage V SS - 0.3 to V CC V V OUT Switch Pin Voltage V SS - 0.3 to V CC V P D Power Dissipation

Internally limited mW

T J Operating Junction Temperature Range -40 to +125 o C T ST Storage Temperature Range

-65 to +150

Caution: The absolute maximum ratings are rated values exceeding which the product could suffer physical damage.

These values must therefore not be exceeded under any conditions.

Recommended Operating Conditions

Symbol Parameter Min

Max Unit V IN Input Voltage (Note 4) 3.6

I OUT Output Current 0 3 A T A Operating Ambient Temperature

-20

+85

o C

Notes: 4. For the operations in low input voltage, AP1538 can tolerate down to 3.6V but max output current loading will be less than 3A. For nominal

applications in such low input voltage range, especially lower than 4V, a higher ROCSET with larger heat sink is recommended.

Electrical Characteristics

(V IN = 12V, T A = 25°C, unless otherwise specified) Symbol Parameter Conditions Min Typ. Max Unit V FB Feedback Voltage I OUT = 0.1A 0.784 0.8 0.816V I FB Feedback Bias Current I OUT = 0.1A

- 0.1 0.5 μA I SHDN Current Consumption During

Power Off V EN = 0V

- 10 - μA ?V OUT

/ V IN

Line Regulation

V IN = 5V~18V

?V OUT

/ V OUT

Load Regulation I OUT = 0.1 to 3A - 0.2 0.5 %

f OSC Oscillation Frequency Measure waveform at SW pin 240 300 400 KHz

f OSC1 Frequency of Current Limit or

Short Circuit Protection Measure waveform at SW pin - 50 - KHz

V IH Evaluate oscillation at SW pin 2.0 - -

V IL EN Pin Input Voltage Evaluate oscillation stop at SW pin - - 0.8 V I SH EN Pin High - 20 - μA

I SL EN Pin Input Leakage Current EN Pin Low - -10 - μA I OCSET OCSET Pin Bias Current -- 75 90 105 μA

V IN =5V, V FB =0V - 110 -

R DS(ON) Internal MOSFET R DS(ON)

V IN =12V, V FB =0V -

70 - m ? EFFI Efficiency

V IN =12V, V OUT = 5V

I OUT =3A

- 92 - % T SHDN Thermal shutdown threshold - 150 - °C T HYS Thermal shutdown hysteresis - 55 - °C

SOP-8L (Note 5) 24 θJC Thermal Resistance Junction-to-Case SOP-8L-DEP (Note 5) - 26

- o

C/W

Notes: 5. Test condition for SOP-8L and SOP-8L-DEP: Devices mounted on 2oz copper, minimum recommended pad layout on top & bottom layer with thermal vias, double sided FR-4 PCB.

Typical Application Circuit

V OUT = V FB x (1+R A /R B )

R B = 0.7K~5K ohm

Notes: 6. Suggested DIODES Power Schottky P/N: B340 series or PDS340.

7. Suggested C OUT for V OUT < 1V; 680μF.

8. Typical feedback compensation (Cc): 5600pF.

Typical Performance Characteristics

Typical Performance Characteristics (Continued)

V OUT Ripple

(V IN = 12V, V OUT = 3.3V, I OUT = 0.1A)

V OUT Ripple

(V IN = 12V, V OUT = 3.3V, I OUT = 3.0A)

Load Transient Response

(V IN = 12V, V OUT = 3.3V, I OUT = 0.1~3A)

Test Circuit

Functional Description

PWM Control

The AP1538 is a DC/DC converter that employs pulse width modulation (PWM) scheme. Its pulse width varies in the range of 0% to 99%, based on the output current loading. The output ripple voltage caused by the PWM high frequency switching can easily be reduced through an output filter. Therefore, this converter provides a low ripple output supply over a broad range of input voltage & output current loading

Under Voltage Lockout

The under voltage lockout circuit of the AP1538 assures that the high-side MOSFET driver remains in the off state whenever the supply voltage drops below 3.3V. Normal operation resumes once V CC rises above 3.5V.

Current Limit Protection

The current limit threshold is set by external resistor R OCSET connected from V CC supply to OCSET pin. The internal sink current I OCSET (90uA typical) across this resistor sets the voltage at OCSET pin. When the PWM voltage is less than the voltage at OCSET, an over-current condition is triggered.

The current limit threshold is given by the following equation:

R I R I OCSET OCSET DS(ON)PEAK ×=×

(I I (MAX) OUT PEAK

Δ+

where,

OUT

S OUT V V L F V V I ×

×?=

ΔIN

I PEAK is the output peak current; R DS (ON) is the MOSFET ON resistance; F S is the PWM frequency (300KHz typical). Also, the inductor value will affect the ripple current ΔI.

The above equation is recommended for input voltage range of 5V to 18V. For input voltage lower than 5V or ambient temperature over 100°C, higher R OCSET is recommended.

The recommended minimum R OCSET value is summarized below:

V IN (V) V OUT

(V) 5V 12V 18V 0.8 4.7K 3.0K 3.3K 1.0 5.6K 3.0K 3.9K 1.2 5.6K 3.0K 3.9K 1.8 5.6K 3.0K 3.9K 2.5 5.6K 3.0K 3.9K 3.3 5.6K 3.0K 3.9K 5.0 N/A 3.0K 4.7K

Inductor Selection

For most designs, the operates with inductors of 22μH to 33μH. The inductor value can be derived from the following equation:

()osc

L ON

OUT IN f I T V V L ×Δ×?=

Where ΔI L is inductor Ripple Current. Large value inductors lower ripple current and small value inductors result in high ripple current. Choose inductor ripple current approximately 15% of the maximum load current 3A, ?I L =0.45A. The DC current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation (3A+0.225A).

Input Capacitor Selection

This capacitor should be located close to the IC using short leads and the voltage rating should be approximately 1.5 times the maximum input voltage. The RMS current rating requirement for the input capacitor of a buck regulator is approximately 1?2 the DC load current. A low ESR input capacitor sized for maximum RMS current must be used. A 470μF low ESR capacitor for most applications is sufficient.

Output Capacitor Selection

The output capacitor is required to filter the output voltage and provides regulator loop stability. The important capacitor parameters are the 100KHz Equivalent Series Resistance (ESR), the RMS ripples current rating, voltage rating and capacitance value. For the output capacitor, the ESR value is the most important parameter. The output ripple can be calculated from the following formula.

ESR I V L RIPPLE ×Δ=

The bulk capacitor’s ESR will determine the output ripple voltage and the initial voltage drop after a high slew-rate transient.

An aluminum electrolytic capacitor's ESR value is related to the capacitance and its voltage rating. In most case, higher voltage electrolytic capacitors have lower ESR values. Most of the time, capacitors with much higher voltage ratings may be needed to provide the low ESR values required for low output ripple voltage.

PCB Layout Guide

If you need low T C & T J or large PD (Power Dissipation), The dual SW pins(5& 6) and Vss pins(7& 8)on the SOP-8L package are internally connected to die pad, The evaluation board should be allowed for maximum copper area at output (SW) pins.

1. Connect FB circuits (R 1, R 2, C 1) as closely as possible and keep away from inductor flux for pure V FB .

2. Connect C3 to Vcc and Vss pin as closely as possible to get good power filter effect.

3. Connect R4 to Vcc and OCSET pin as closely as possible.

4. Connect ground side of the C2 & D1 & C4 as closely as possible and use ground plane for best performance.

Functional Description (Continued)

V OUT

Figure: Layout numbering comparison.

Marking Information

(1) SOP-8L

( Top View )

SOP-8L

AP1538Logo Part No Year : "07" =2007 "08" =2008

Xth week:01~52~

G : Green

(2) SOP-8L-DEP

( Top View )

SOP-8L-DEP

Logo Part No Internal code Year : "07" =2007 "08" =2008

Xth week:01~52~

G : Green

E : SOP-8L-DEP

Package Information ( All Dimensions in mm ) (1) SOP-8L

Detail "A"

(Unit: mm)

(2) SOP-8L-DEP

Bottom view

IMPORTANT NOTICE

Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes without further notice to any product herein. Diodes Incorporated does not assume any liability arising out of the application or use of any product described herein; neither does it convey any license under its patent rights, nor the rights of others. The user of products in such applications shall assume all risks of such use and will agree to hold Diodes Incorporated and all the companies whose products are represented on our website, harmless against all damages.

LIFE SUPPORT

Diodes Incorporated products are not authorized for use as critical components in life support devices or systems without the expressed written approval of the President of Diodes Incorporated.