Datasheet AT1380A Datasheet (AIM)

AT1380A

Switching Regulator Controller for LCD Bias

Features

•2.5 to 15 V supply voltage operating range.

•Low current consumption: 6 mA in operation,
1 µA or less in stand-by.

•20 kHz to 1 MHz operation frequency range.

•Provides a fixed output current with minimal
supply voltage fluctuations by using an external
resistor to set the output current.

• Totem-pole output.

• Built-in soft start circuit.

• Built-in timer-latch short circuit detection and
protection circuit (SCP).

Applications

• LCD Displays

• PDAs

• Digital Still Cameras

Block Diagram

General Description

The AT1380A is a single-channel PWM control IC
for DC/DC conversion with soft start function and
short circuit detection. Adjustable soft start is
programmed with an external capacitor on SCP
pin. The AT1380A is ideal for up, down and fly­back conversion.

2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: [phone] WWW: http://www.aimtron.com.tw
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AT1380A

Switching Regulator Controller for LCD Bias

Pin Configuration

Ordering Information

Part number Package Remarks

AT1380A 8-pin Plastic SOP AT1380AS
AT1380A 8-pin TSSOP AT1380AP

Pin Description

Pin No. Symbol I/O Description

1 IN- I Error amplifier inverting input
2 SCP — Soft start and SCP setting capacitor connection
3 VCC — Power supply
4 BR/CTL I Output current setting
5 OUT O Totem-pole type output
6GND—Ground
7 OSC — Capacitor and resistor connection pin for setting the oscillation

frequency

8 FB O Error amplifier output

2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
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AT1380A

Switching Regulator Controller for LCD Bias

Absolute Maximum Ratings

(Ta=+250C)

Rated ValueParameter Symbol Condition

Unit

Min. Max.

Power supply voltage V
Output source current I
Output sink current I
Allowable dissipation

Operating temperature T
Storage temperature T

CC

+

O

-

O

P

D

P

D

OP

stg

SOP-8, Ta ≦+25°C

TSSOP-8, Ta ≦+25°C

——15V
——-50mA
——50mA

—570 mW
—430 mW

—-30+85
— -55 +125

0

C

0

C

ESD Classification MIL-STD-883 Class 2

* : When mounted on a 10 cm square double-sided epoxy board

WA R N IN G : Do not exceed these ratings. IC devices can be permanently damaged by stress (voltage,
current, temperature, etc.) in excess of absolute maximum ratings.

Recommended Operating Conditions

(Ta=+250C)

Va lu esParameter Symbol

Min. Typ. Max.

Power supply voltage V
Error amplifier input voltage V
BR/CTL pin input voltage V
Output source current I
Output sink current I
SCP pin capacitance C
Phase compensation capacitance C
Output current setting resistance R

Timing resistance R
Timing capacitance C

Oscillation frequency f
Operating temperature T

O

O

OSC

OP

CC

BR

PE

I

+

-

P

B

T

T

2.5 -- 13.5

-0.2 -- 1.0

-0.2 -- V

CC

-20 -- --

-- -- 40

-- 0.1 --

-- 0.1 --

150 390 5000 Ω

1.0 3.0 10.0

100 270 10000 pF

10 500 1000 kHz

-30 +25 +85 °C

WA R N IN G : Recommended operating conditions are normal operating ranges for the IC device. All
the device’s electrical characteristics are warranted for operation within these ranges. Use IC devices
only within the recommended operating conditions. Operation outside these ranges may adversely
affect the reliability and can result in device failure.

Unit

Ｖ
Ｖ

Ｖ
ｍＡ
ｍＡ
μＦ
μＦ

ｋΩ

2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
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AT1380A

Switching Regulator Controller for LCD Bias

Electrical Characteristics

(VCC=+3.0V, Ta=+250C)

Va lu esParameter Symbol Condition

Min. Typ. Max.

Lockout
(U.V.L.O.)

Reset voltage for
falling Vcc. OUT
remains off if Vcc is
below this level.

Startup voltage for
rising Vcc.

V

R

-- 1.8 1.9 VVCC Under voltage

--

V

TH

2.4 2.5 2.6 V

Unit

Soft start

Short circuit
detection (S.C.P.)

Sawtooth waveform
oscillator (OSC)

Error amplifier

Idle period
adjustment section

Output section

Charging current I

Voltage at soft start

V

CS

V

ts

=0V -1.5 -1.0 -0.7

SCP

-- 0.7 0.8 0.9 V

μA

completion
Charging current I

Threshold voltage V
Oscillation frequency f

Frequency input

V

CPC

OSC

f

tPC

∆V

=0V -1.5 -1.0 -0.7

SCP

-- 0.7 0.8 0.9 V

RT=3kΩ, CT=270pF

400 500 600 kHz

VCC=2.5V to 13.5V -- 2 10 %

μA

Stability
Frequency variation

f

Ta =-300C to 850C--5--%

∆T

with temperature
Input threshold

V

V

T

= 450mV 480 500 520 mV

FB

Voltage
VT input stability V
VT variation with

V

VCC=2V to 13.5V -- 5 20 mV

T∆V

Ta = -300C to 850C--1--%

T∆T

Temperature
Input bias current I

Voltage gain A
Frequency bandwidth BW AV = 0 dB -- 6 -- MHz

V

voltage range

V

Output source current I
Output sink current I
Maximum duty cycle T

V
V

Output voltage

V

V

Output source current I

Output sink current I

Pull down resistance R

VIN = 0V -1.0 -0.2 1.0

B

V

+

OM

_

OM

+

V

OM

OM

DUTY

OH1

OH2

OL1

OL2

O

O

FB

_

RT=3.3kΩ, CT=270pF
f

OSC

RB= 390Ω, IO= -15 mA
RB= 750Ω, VCC = 3.0V

= -10 mA

I

O

RB= 390Ω, IO= -15 mA

RB= 750Ω, VCC = 3.0V

= -10 mA

I

O

+

RB= 390Ω, VO = 0.9V

-

RB= 390Ω, VO = 0.3V

O

-- 70 100 145 V/V

--

0.78 0.87 -- VMaximum output

= 450mV

= 500KHz

-- 20 30 40

μA

-- 0.05 0.2 V

-- -40 -24

24 40 --

μA
μA

75 -- 85 %

1.0 1.2 -- V

0.8 1.0 -- V

-- 0.1 0.2 V

-- 0.1 0.2 V

-- -40 -30 mA

40 70 -- mA

ｋΩ

2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: [phone] WWW: http://www.aimtron.com.tw
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AT1380A

Switching Regulator Controller for LCD Bias

0.10 0.19 0.25 V

-20 -- 0

-- -- -45

-1.8 -- -0.1

-- -- 1

-- 6 10.0

Output current
Setting section/
Control section

Entire device

Pin voltage V

Input off condition I

Input on condition I

Pin current range I

Stand-by current I

Average supply current I

RB= 390Ω

BR

OFF

ON

BR

BR/CTL pin open or

CCS

V

CC

RB= 390,

CC

=2.5~13.5V

V

CC

--

Timing Chart

μA

μA

ｍＡ

μA

ｍＡ

2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
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AT1380A

Switching Regulator Controller for LCD Bias

Typical Application Schematic

2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: [phone] WWW: http://www.aimtron.com.tw
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AT1380A

Switching Regulator Controller for LCD Bias

2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: [phone] WWW: http://www.aimtron.com.tw
Fax: [phone] Email: [e-mail]

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AT1380A

Switching Regulator Controller for LCD Bias

Functional Description

Soft Start SCP

Figure 1. Soft-Start SCP circuit

At power-on, the AT1380A enters the soft-start mode to prevent current spike and overshoot. The

capacitor CS is charged from 0V at a constant current of 1µA.

The soft-start time for the duty cycle to reach 50%

)(35.0 FCSt

µ

S

When V

the SCP function. If the output load conditions change rapidly causing the output to drop suddenly, the

external capacitor CS will start to charge because the error amplifier output (FB pin) is fixed at V

When the external capacitor is charged above 0.8V, the output pin is set low. Once the latch circuit has

set, the capacitor CS will be discharged to low state and the latch circuit will not reset until power is

turned off or the power supply is restarted.

Short-circuit detection time (or full soft-start time) :

reaches 0.8V, the AT1380A leaves the soft-start mode to enter the normal mode and enable

SCP

PE

×=

OM

µ

×=

)(8.0 FCSt

.

+

2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: [phone] WWW: http://www.aimtron.com.tw
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AT1380A

Switching Regulator Controller for LCD Bias

Setting Oscillating Frequency

The oscillator circuit generates a triangular sawtooth wave with a peak of 0.8V and a trough of 0.1V

using the timing capacitor (CT) and the timing resistor (RT) that are connected to the OSC pin. This

oscillator can provide oscillating frequency in the range from 20KHz to 1MHz. The waveform of the

OSC pin is shown as Figure 2.

Figure 2 Oscillator Waveform

The cycle (T) can be determined as follows:

t

−

RTCT

VHeVX

=

Switching Regulator Function

(1) Reference voltage circuit

A temperature-compensated reference voltage (~1.25V) is generated by the reference voltage

circuit from the voltage supplied by the power supply pin (pin 3). The circuit also sets the idle

period besides providing the reference voltage for the switching regulator.

(2) Error amplifier

The error amplifier detects the output voltage of the switching regulator and sets the PWM

control signal. The voltage gain is fixed. The system is made stable by connecting a phase

×

e

RTCTt

××−=

VX

)(log

e

VH

[]

sRTCTRTCTT

××=××−= 1.2)8.0/1.0(log

compensation capacitor to the FB pin (pin 8).

(3) PWM comparator

The voltage comparator includes one inverting and three non-inverting inputs. The comparator is

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AT1380A

Switching Regulator Controller for LCD Bias

a voltage to pulse width converter that controls the ON time of the output pulse depending on the

level of input voltage. The output level remains high when the sawtooth wave is lower than the

error amplifier output voltage, the soft start setting voltage, and the idle period setting voltage.

(4) Output circuit

The output circuit can drive an external NPN transistor directly and has a totem pole

configuration. The value of the ON/OFF current can be set by a resistor connected to the

BR/CTL pin (pin 4). Stand-by mode (supply current 1µA or less) can be set by connecting the

BR/CTL pin (pin4) to VCC or by making the pin open.

(5) Under-Voltage Lockout (UVLO)

Transients during powering on or instantaneous glitches in the supply voltage can cause the

control IC to malfunction and damage the system. To prevent malfunction at low input voltage,

the circuit compares the supply voltage to the internal reference voltage to detect a low input

voltage. Once detected, the circuit sets the output pin low.

To cancel the status, set V

recommended operation range and the latch will be restored to operate normally.

below the reset voltage VR (0.9V) and then set VCC up to the

CC

2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
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AT1380A

Switching Regulator Controller for LCD Bias

Small Outline 8-pin Plastic SOL

SYMBOL

INCHES MILLIMETERS

MIN MAX MIN MAX

NOTES

A 0.188 0.197 4.80 5.00 ­B 0.149 0.158 3.80 4.00 ­C 0.228 0.244 5.80 6.20 ­D 0.050 BSC 1.27 BSC ­E 0.013 0.020 0.33 0.51 -

F 0.004 0.010 0.10 0.25 -

H 0.053 0.069 1.35 1.75 -

J 0.011 0.019 0.28 0.48

K 0.007 0.010 0.19 0.25 -

M 0.016 0.050 0.40 1.27

L 0.150 REF 3.81 REF -

e1 45

α

0

0

0

0

8

0

0

45

0

0

8

-

-

2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
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AT1380A

Switching Regulator Controller for LCD Bias

Small Outline 8-pin TSSOP

SYMBOL

INCHES MILLIMETERS

MIN MAX MIN MAX

NOTES

A 0.114 0.122 2.90 3.10 ­B 0.169 0.177 4.30 4.50 ­C 0.244 0.260 6.20 6.60 ­D 0.026 BSC 0.65 BSC ­E 0.010 0.012 0.25 0.30 -

F 0.002 0.006 0.05 0.15 ­H 0.041 0.047 1.05 1.20 ­K 0.005 BSC 0.127 BSC -

M 0.020 0.028 0.50 0.70

α

0

0

0

8

0

0

0

8

-

2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
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C

AT1380A

Switching Regulator Controller for LCD Bias

Reflow Condition (IR/Convection or VPR Reflow)

Reference JEDEC Standard J-STD-020A

Classification Reflow Profiles

Convection or

IR/Convction

Average Heating Rate(180°C to peak)
Preheat Temperature(125±20°C)
Temperature maintained above 180°C
Time within 5°C of actual Peak Temperature
Peak Temperature Range(Note 1)

Cooling Rate
Time 25°C to Peak Temperature

*1 The maximum peak temperatures for IR and VP reflow are depending on package dimensions.

5

°C/second max.

120 seconds max.
10~150 seconds
10~20 seconds 60 seconds

219~225°C or
235~240°C
6°C /second max. 10°C/second max.
6 minutes max.

Package Reflow Conditions

Pkg. Thickness ≥2.5mm
and all bags

Convection 219~225
VPR 219~225

°C

IR/Convection 219~225

°C

°C

Pkg. Thickness <2.5mm
and

Pkg. Volume ≥350 mm

Pkg. Thickness <2.5mm
and

3

Pkg. Volume <350 mm

Convection 235~240
VPR 235~240
IR/Convection 235~240

VPR

10

°C/second max.

219~225°C or
235~240°C

°C

3

°C

°

2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: [phone] WWW: http://www.aimtron.com.tw
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