R1285L201A [RICOH]

Switching Regulator, 1600kHz Switching Freq-Max, 2.70 X 3 MM, DFN-12;


型号：	R1285L201A
厂家：	RICOH ELECTRONICS DEVICES DIVISION
描述：	Switching Regulator, 1600kHz Switching Freq-Max, 2.70 X 3 MM, DFN-12 开关
文件：	总12页 (文件大小：241K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

R1285L series

2ch DCDC for OLED

NO.EA-209-090703

OUTLINE

The R1285L 2ch DC/DC converter is designed for OLED Display power source. It contains a step up DC/DC

converter and an inverting DC/DC converter to generate two required voltages by OLED Display.

Step up DC/DC converter generates boosted output voltage to 4.6V ~ 5.0V. Inverting DC/DC converter generates

negative voltage –2.0V ~ -6.0V independently. Each of the R1285 series consists of an oscillator, a PWM control

circuit, a voltage reference, error amplifiers, over current protection circuits, short protection circuits, an under

voltage lockout circuit (UVLO), a complete shutdown switch and an Nch driver for boost operation, a Pch driver for

inverting, and so on. A high efficiency boost and inverting DC/DC converter can be composed with external

inductors, diodes, capacitors and resistors. Start up sequence is internally made.

FEATURES

ꢀ

Operating Voltage • • • • • 2.3V ~ 4.8V

Step Up DC/DC (CH1)

Internal Pch MOSFET for complete shutdown (Ron=300mΩTyp.)

Internal Nch MOSFET Driver (Ron=300mΩTyp.)

Output Voltage (V_OUTP

) • • • • • 4.6V ~ 5.0V (0.2VStep)

Auto Discharge function for positive output

Internal Soft start function (Typ. 4.5ms)

Over Current Protection

Maximum Duty Cycle: 85%(Typ.)

ꢀ

Inverting DC/DC (CH2)

Internal Pch MOSFET Driver (Ron=600mΩ Typ.)

Output Voltage (V_OUTN

Adjustable Vout Up to -6V with external resistors

Auto Discharge function for negative output

Internal Soft start function (Typ. 4.5ms)

Over Current Protection

)

• • • • • -2V ~ -6V (0.1VStep)

[ R1285LxxxA ]

[ R1285L00xB ]

Maximum Duty Cycle: 90%(Typ.)

Control

Short Protection with timer latch function (Typ. 50ms)

Short condition for either or both two outputs makes all output drivers off and latches. If the

maximum duty cycle continues for a certain time, these output drivers will be turned off. This

function prevents irregular current from overheating the R1285 .

CE with start up sequence function ( CH1→CH2 )

UVLO function.

Operating Frequency • • • • • 1400kHz

Small package • • • • • DFN12 ( 2.7mm x 3.0mm )

APPLICATION

ꢀ

Fixed voltage power supply for portable equipment

Fixed voltage power supply for OLED

V 1.4

R1285L

BLOCK DIAGRAM

●R1285LxxxA

PV_CC

L_XP1

L_XP2

Current

Limit

Osc

Maxduty

PWM

Control

PWM

Control

Timer

L_XN

Maxduty

Current

Limit

Short

Protect

PGND

V_OUTP

Discharge

Control

Discharge

Control

V_OUTN

TST1

Vref3

Vref2

Vref1

Soft start1

TST2

Sequence

Control

Soft start2

Enable

Control

UVLO

V_CC

GND

●R1285L00xB

PV_CC

L_XP1

L_XP2

Current

Limit

Osc

Maxduty

PWM

Control

PWM

Control

Timer

L_XN

Maxduty

Current

Limit

Short

Protect

PGND

V_OUTP

Discharge

Control

Discharge

Control

V_OUTN

V_FBN

V_REF

Vref3

Vref2

Vref1

Soft start1

Sequence

Control

Soft start2

Enable

Control

UVLO

V_CC

GND

R1285L

SELECTION GUIDE

The mask option for the ICs can be selected at the user's request. The selection can be made with designating the

part number as shown below.

←Part Number

R 1 2 8 5 L X X X X

code

contents

Setting inverting output voltage (V_OUTN

)

Stepwise setting with a step of 0.1V in the range of -2.0V to -6.0V is possible for

fixed output version (R1285LXXXA)

"00" is for Output Voltage Adjustable version (R1285L00XB)

Setting positive output voltage (V_OUTP

)

1: 4.6V

2: 4.8V

3: 5.0V

Designation of method of setting V_OUTN

A: Fixed output version

B: Adjustable version

PIN CONFIGURATION

● DFN -2730-12

Bottom View

Top View

R1285L

PIN DESCRIPTIONS

●R1285LxxxA

PIN No.

NAME

PGND

V_OUTP

PV_CC

V_CC

FUNCTION

Power GND pin

Output Voltage feedback pin for Step up DC/DC

Power input pin

Analog power source input pin

Analog GND pin

GND

Chip enable pin

TST2

TST1

V_OUTN

L_XN

TEST pin

Output Voltage feedback pin for Inverting DC/DC

Switching pin for Inverting DC/DC

Shutdown switch output pin

Switching pin for Step up DC/DC

L_XP1

L_XP2

●R1285L00xB

PIN No.

NAME

PGND

V_OUTP

PV_CC

V_CC

FUNCTION

Power GND pin

Output Voltage feedback pin for Step up DC/DC

Power input pin

Analog power source input pin

Analog GND pin

GND

Chip enable pin

V_REF

V_FBN

V_OUTN

L_XN

Reference voltage output pin for Inverting DC/DC

Feedback pin for Inverting DC/DC

Output Voltage feedback pin for Inverting DC/DC

Switching pin for Inverting DC/DC

Shutdown switch output pin

L_XP1

L_XP2

Switching pin for Step up DC/DC

R1285L

ABSOLUTE MAXIMUM RATINGS

(GND / PGND=0V)

Item

V_CC/ PV_CCpin Voltage

V_OUTPpin Voltage

Symbol

V_CC

Rating

6.0

Unit

V_OUTP

V_CE

-0.3 ~ 6.0

CE pin Voltage

-0.3 ~ V_CC+0.3

-0.3 ~ 6.0

L_XP1 pin Voltage

V_LXP

L_XP2 pin Voltage

V_LXP

L_XNpin Voltage

V_LXN

V_OUTN

V_TST

V_FBN

V_REF

V_CC-14 ~ V_CC+0.3

-0.3 ~ V_CC+0.3

-0.7^*2~ V_CC+0.3

1000

V_OUTNpin Voltage

TST1/TST2 pin Voltage [R1285LxxxA]

V_FBNpin Voltage [R1285L00xB]

V_REFpin Voltage [R1285L00xB]

Power Dissipation^*1

ºC

Operating Temperature Range

Storage Temperature Range

-40 ~ +85

Tstg

-55 ~ +125

∗1) For Power Dissipation, please refer to PACKAGE INFORMATION to be described.

∗2)In case the voltage range is from –0.7V to –0.3V, permissible current is 10mA or less.

ABSOLUTE MAXIMUM RATINGS

Absolute Maximum ratings are threshold limit values that must not be exceeded ever for an

instant under any conditions. Moreover, such values for any two items must not be reached

simultaneously. Operation above these absolute maximum ratings may cause degradation or

permanent damage to the device. These are stress ratings only and do not necessarily imply

functional operation these limits.

R1285L

ELECTRICAL CHARACTERISTICS

(Ta=25ºC)

Symbol

V_CC

I_CC1

Item

Conditions

MIN.

2.3

TYP. MAX. Unit.

4.8

Operating Input Voltage

V_CCConsumption Current

4.0

V_CC=4.8V

(switching)

V_CCConsumption Current

(at no switching)

350

I_CC2

0.1

I_STB

Standby Current

V_CC=4.8V

Falling

V_UVLO

UVLO Detect Voltage

1.95

2.05

2.15

2.28

V_UVLO1

+0.10

V_UVLO

UVLO Released Voltage

Rising

1200 1400 1600 kHz

F_OSC

T_DLY

V_CEL

V_CEH

R_CE

Oscillator Frequency

Delay Time for Protection

CE “L” Input Voltage

CE “H” Input Voltage

V_CC=3.7V

V_CC=2.3V

V_CC=4.8V

0.3

1.5

600

kΩ

CE pin Pulldown Resistance V_CC=3.7V

■Boost DC/DC

x0.985

x1.015

V_OUTP

V_OUTPVoltage Tolerance

V_CC=3.7V

V_CC=3.7V , -40ºC Ta 85ºC

∆V_OUTP

/∆T

∆V_OUTP

/∆Vcc

∆V_OUTP

/∆I_OUT

V_OUTPVoltage

Temperature Coefficient

V_OUTPVoltage

Line Regulation

V_OUTPVoltage

ppm

/ºC

150

±4

±10

2.9V V_CC3.4

V_CC=3.7V , 10mA I_OUT100mA

Load Regulation

V_OUTPVoltage

∆V_{OUTP_TR}

V_CC=2.9V ↔ 3.4V , T_R=T_F=50us

Line Transient Response

4.5

300

mΩ

Maxduty1 CH1 Max. Duty Cycle

V_CC=3.7V

T_SS1

CH1 Soft-Start Time

L_XP1 ON Resistance

V_CC=3.7V

R_LXP1

V_CC=3.7V

I_{OFF LXP1}L_XP1 Leakage Current

R_LXP2L_XP2 ON Resistance

I_{OFF LXP2}L_XP2 Leakage Current

V_CC=4.8V , V_LXP1=0V

V_CC=3.7V

300

V_CC=4.8V , V_LXP2=5V

V_CC=3.7V

0.7

1.0

I_LIMLXP2

I_VOUTP

L_XP2 Current Limit

V_OUTPDischarge Current

V_CC=3.7V , V_OUTP=0.1V

R1285L

■Inverting DC/DC [ R1285LxxxA]

x0.985

x1.015

V_OUTN

V_OUTNVoltage Tolerance

V_CC=3.7V

∆V_OUTN

/∆T

∆V_OUTN

/∆Vcc

∆V_OUTN

/∆I_OUT

V_OUTNVoltage

Temperature Coefficient

V_OUTNVoltage

Line Regulation

V_OUTNVoltage

ppm

/ºC

V_CC=3.7V , -40ºC≦Ta≦85ºC

150

±6

2.9V≦V_CC≦3.4

±15

±25

V_CC=3.7V , 10mA≦I_OUT≦100mA

V_CC=2.9V ↔ 3.4V , T_R=T_F=50us

Load Regulation

∆V_{OUTN_TR}V_OUTNVoltage

Line Transient Response

Maxduty2 CH2 Max. Duty Cycle

4.5

600

mΩ

V_CC=3.7V

T_SS2

CH2 Soft-Start Time

L_XNON Resistance

L_XNLeakage Current

L_XNCurrent Limit

V_CC=3.7V

R_LXN

V_CC=3.7V

I_{OFF LXN}

I_LIMLXN

I_VOUTN

V_CC=4.8V , V_LXN=-6V

V_CC=3.7V

1.0

-25

1.5

V_OUTNDischarge Current

V_CC=3.7V , V_OUTN=-0.3V

■Inverting DC/DC [ R1285L00xB]

μA

V_FBN

V_CC=3.7V

V_FBNvoltage tolerance

-0.1

0.1

I_FBN

V_CC=4.8V , V_FBN=0V or 4.8V

V_FBNinput current

1.172

1.2

1.228

V_REF

V_CC=3.7V

V_REFvoltage tolerance

+V_FBN+V_FBN+V_FBN

∆V_REF

/∆T

∆V_OUTN

V_REFvoltage

temperature coefficient

V_OUTNVoltage

V_CC=3.7V

-40ºC≦Ta≦85ºC

ppm

/ºC

±150

±6

2.9V≦V_CC≦3.4

/∆V_CC

Line Regulation

∆V_OUTN

/∆I_OUT

V_OUTNVoltage

±15

±25

V_CC=3.7V , 10mA≦I_OUT≦100mA

V_CC=2.9V ↔ 3.4V , T_R=T_F=50us

Load Regulation

∆V_{OUTN_TR}V_OUTNVoltage

Line Transient Response

4.5

600

mΩ

Maxduty2 CH2 Max. Duty Cycle

V_CC₌3.7V

T_SS2

CH2 Soft-Start Time

L_XNON Resistance

L_XNLeakage Current

L_XNCurrent Limit

V_CC₌3.7V

R_LXN

V_CC₌3.7V

I_{OFF LXN}

I_LIMLXN

I_VOUTN

V_CC=4.8V , V_LXN=-6V

V_CC=3.7V

1.0

1.5

V_OUTNDischarge Current

V_CC=3.7V , V_OUTN=-0.3V

* In terms of TST pin(TST1 , TST2), connect the GND level or remain it open.

RECOMMENDED OPERATING CONDITIONS (ELECTRICAL CHARACTERISTICS)

All of electronic equipment should be designed that the mounted semiconductor devices operate within the

recommended operating conditions. The semiconductor devices cannot operate normally over the recommended

operating conditions, even if when they are used over such conditions by momentary electronic noise or surge. And the

semiconductor devices may receive serious damage when they continue to operate over the recommended operating

conditions.

R1285L

TYPICAL APPLICATION AND TECHNICAL NOTES

●R1285LxxxA

V_OUTP

10uF

PGND

V_OUTP

PV_CC

V_CC

L_XP2

L_XP1

L_XN

V_OUTN

4.7uF

10uF

GND

TST1

TST2

EN control

●R1285L00xB

V_OUTP

10uF

PGND

V_OUTP

PV_CC

V_CC

L_XP2

L_XP1

L_XN

R2 R3

R1 C4

V_OUTN

V_FBN

V_REF

4.7uF

10uF

GND

EN control

●Set a ceramic 4.7μF or more capacitor between Vcc and GND as C1.

●Set a ceramic10μF or more capacitor between V_OUTPand GND, and between V_OUTNand GND for each as

C2 and C3.

●Start up Sequence

When CE level turns from ‘L’ to ‘H’ level, the softstart of CH1 starts the operation. After detecting output voltage of

CH1(V_OUTP)as the nominal level, the soft start of CH2 starts the operation.

CH1 (V_OUTP

)

Soft start CH1

Soft Start CH2

CH2 (V_OUTN

)

R1285L

●Auto Discharge Function

When CE level turns from ‘H’ to ‘L’ level, the R1285 goes into standby mode and switching of the outputs of

_XP2and L_XNwill stop. Then dischage switsh between V_OUTNand PV_CCand switch between V_OUTPand GND

turn on and discharge the negative output voltage and positive output voltage. When the negative output

voltage is discharged to 0V, the switsh between V_OUTNand PV_CCturns off and the negative output will be Hi-Z.

Positive output voltage is discharged to 0V In standby mode.

If Vcc voltage became lower than UVLO detect voltage , discharge switches also turn on and discharge

output voltage(V_OUTNand V_OUTP) .

In case of timer latch protection,discharge switches will keep off .

V_OUTP

Hi-Z (V_OUTN

0V (V_OUTP

)

V_OUTN

Discharge

)

●Short protection circuit timer

In case that the voltage of V_OUTPdrops, the error amplifier of CH1 outputs "H". In case that the voltage of

V_OUTNrises, the error amplifier of CH2 outputs "L". The built-in short protection circuit makes the internal

timer operate with detecting the output of the error amplifier of CH1 as "H", or the output of the error

amplifier of CH2 as "L". After the setting time will pass, the switching of L_XP2and L_XNwill stop and shutdown

switch will turn off and both of discharge switches will keep off .

To release the latch operation, make the Vcc set equal or less than UVLO level and restart or set the CE pin

as "L" and make it "H" again.

During the softstart operation of CH1and CH2, the timer operates independently from the outputs of the

error amplifiers. Therefore, even if the softstart cannot finish correctly because of the short circuit, the

protection timer function will be able to work correctly.

Amp output for Boost

Amp output for Inverting

Normal state

Short state

Latch state

Shutdown

Timer function (Typ. 50ms)

During a timer function, current is

After shutdown

restricted by current limit protection drivers and shutdown

or maxduty function until shutdown . switch turn off

R1285L

●Inverting DC/DC converter output voltage setting [ R1285L00xB ]

The output voltage V_OUTNof the inverting DC/DC converter is controlled with maintaining the V_FBNas 0V.

V_OUTNcan be set with adjusting the values of R1 and R2 as in the next formula.

V_OUTN= V_FBN- (V_REF-V_FBN) x R2 / R1

DC/DC converter’s phase may lose 180 degree by external components of L and C and load current. Because of

this, the phase margin of the system will be less and the atability will be worse. Therefore, the pahse must be

gaind.

A pole will be formed by external components, L and C.

_pole~ 1 / {2 x π x √(L2xC2)}

Zero will be formed with R2 and C4.

_zero~ 1 / (2 x π x R2 x C4)

Set the cutt-off frequency of the Zero close to the cutt-off frequency of the pole by L and C.

If the noise of the system is large, the output noise affects the feedback and the operation may be unstable. In

that case, another resistor R3 will be set. The appropriate value range is from 1kΩ to 5kΩ.

●Set a ceramic 1μF to 2.2μF capacitor between V_REFand GND as C5. [ R1285L00xB ]

Operation of Step-up DC/DC Converter and Output Current

IL2

Inductor

Diode

Lx Tr

I_OUT

V_OUT

V_IN

IL1

Continuous Mode

Discontinuous Mode

ILxmax

ILxmin

Ton

T=1/fosc

Toff

Ton

T=1/fosc

Toff

R1285L

There are two operation modes for the PWM control step-up switching regulator, that is the continuous mode

and the discontinuous mode.

When the LX Tr. is on, the voltage for the inductor L will be VIN. The inductor current (IL1) will be;

IL1 = V_INx T_on/ L ...............................................................................................................Formula1

When the Lx transistor turns off, power will supply continuously. The inductor current at off (IL2) will be;

IL2 = (V_OUT-V_IN) x Tf / L .....................................................................................................Formula2

In terms of the PWM control, when the Tf=Toff, the inductor current will be continuous, the operation of the

switching regulator will be continuous mode.

In the continuous mode, the current variation of IL1 and IL2 are same, therefore

V_INx T_on/ L = (V_OUT-V_IN) x Toff / L

....................................................................................Formula3

In the continuous mode, the duty cycle will be

DUTY = T_on/ (T_on+T_off) = (V_OUT-V_IN) / V_OUT........................................................................Formula4

If the input power equals to output power,

I_OUT= V_IN²x T_on/ (2 x L x V_OUT

)

.......................................................................................Formula5

When I_OUTbecomes more then Formula5, it will be continuous mode.

In this moment, the peak current, ILxmax flowing through the inductor is described as follows:

ILxmax = I_OUTx V_OUT/ V_IN+ V_INx T_on/(2 x L)

ILxmax = I_OUTx V_OUT/ V_IN+ V_INx Tx (V_OUT-V_IN) /(2 x L x V_OUT

..................................................................Formula6

.......................................Formula7

)

Therefore, peak current is more than I_OUT. Considering the value of ILxmax, the condition of input and output,

and external components should be selected.

The explanation above is based on the ideal calculation, and the loss caused by Lx switch and external

components is not included.

The actual maximum output current is between 50% and 80% of the calculation.

Especially, when the IL is large, or VIN is low, the loss of VIN is generated with on resistance of the switch.

As for V_OUT, V_F(as much as 0.3V)of the diode should be considered.

Operation of Inverting DC/DC Converter and Output Current

Lx Tr

Diode

I_OUT

V_OUT

V_IN

IL1

IL2

Inductor

R1285L

Discontinuous Mode

ILxmax

Continuous Mode

ILxmax

ILxmin

Ton

T=1/fosc

Toff

Ton

T=1/fosc

Toff

There are also two operation modes for the PWM control inverting switching regulator, that is the continuous

mode and the discontinuous mode.

When the LX Tr. is on, the voltage for the inductor L will be VIN. The inductor current (IL1) will be;

IL1 = V_INx T_on/ L...................................................................................................................Formula8

Inverting circuit saves energy during on time of Lx Tr, and supplies the energy to output during off time,

output voltage opposed to input voltage is obtained. The inductor current at off (IL2) will be;

IL2 = V_OUTx Tf / L .................................................................................................................Formula9

(The above formula and after, the absolute value of the negative output voltage is assumed to be

V_OUT

: Output voltage= -10V , V_OUT=10 )

In terms of the PWM control, when the T_f=T_off, the inductor current will be continuous, the operation of the

switching regulator will be continuous mode.

In the continuous mode, the current variation of IL1 and IL2 are same, therefore

V_INx T_on/ L = V_OUTx T_off/ L...................................................................................................Formula10

In the continuous mode, the duty cycle will be:

DUTY = T_on/ (T_on+T_off) = V_OUT/ (V_OUT+ V_IN)........................................................................Formula11

If the input power equals to output power,

I_OUT= V_IN²x T_on/ (2 x L x V_OUT) .............................................................................................Formula12

When IOUT becomes more then Formula12 , it will be continuous mode.

In this moment ,the peak current, ILxmax flowing through the inductor is described as follows:

IL_xmax= I_OUTx V_OUT/ V_IN+ V_INx T_on/ (2 x L)...........................................................................Formula13

IL_xmax= I_OUTx V_OUT/ V_IN+ V_INx V_OUTx T / { 2 x L x (V_OUT+ V_IN) }.........................................Formula14

Therefore, peak current is more than I_OUT. Considering the value of ILxmax, the condition of input and output,

and external components should be selected.

The explanation above is based on the ideal calculation, and the loss caused by Lx switch and external

components is not included.

The actual maximum output current is between 50% and 80% of the calculation.

Especially, when the IL is large, or V_INis low, the loss of V_INis generated with on resistance of the switch. As

for V_OUT, V_F(as much as 0.3V)of the diode should be considered.

R1285L201A [RICOH]

相关型号：

R1285L201A-TR

R1285L201A-TR-F

R1285L202A

R1285L202A-TR

R1285L202A-TR-F

R1285L203A

R1285L203A-TR-F

R1285L211A

R1285L211A-TR

R1285L211A-TR-F

R1285L212A

R1285L212A-TR