RICOH R1204x User Manual

R1204x Series

PWM/VFM Step-up DC/DC Converter for White LED / PMOLED and General Use

The R1204x Series are CMOS-based PWM/VFM step-up DC/DC converters, which are optimized to drive white LEDs and OLED with constant current. There are two types. The A/D versions are optimized for the general use or the drive of PMOLED, and the B/C/E/F version is optimized for the serial drive of white LED with constant current. The R1204x includes an under-voltage lockout circuit (UVLO), a soft-start circuit, and an over-voltage protection circuit (OVP), a thermal shutdown circuit. By simply using an inductor, divider resisters, and capacitors as external components, OLED and white LEDs can be driven with high efficiently. The A/D version can set white LED current with feedback resister (R1). The brightness of the LEDs and the soft-start time can be adjusted by applying a PWM signal (200Hz to 300kHz) to the CE pin. In addition to DFN(PLP)1820-6, 0.95mm thickness TSOT-23-6 is available.

FEATURES

• Supply Current (IDD)························Typ. 800μA (VIN= 5.5V, VFB = 0V, Lx at no load)	• UVLO Detect Voltage (VUVLO)·······Typ. 2.0V
• Standby Current (Istandby)··················Max. 5μA (VIN= 5.5V, VCE = 0V)	• Coil-current Limit Circuit ··············Current Limit Typ. 900mA
• Input Voltage Range (VIN)···············2.3V to 5.5V	• Over Voltage Protection Circuit (OVP) ···Typ. 23V, Typ. 33V, Typ. 42V
• Feedback Voltage (VFB) ·················0.2V (A/D Version)	• Soft Start Time (tstart)·····················Controllable by PWM signal
1.0V (B/C/E/F Version)	to the CE pin (A/D Version)
• Feedback Voltage Accuracy ···········± 10mV (A/D Version)	Typ. 10ms (B/C/E/F Version)
± 15mV (B/C/E/F Version)	• Thermal Shutdown Circuit ···········Stops at 150°C
• Oscillator Frequency (fosc)···············1MHz (A/B/C Version), 750kHz (D/E/F Version)	• Packages ·····································DFN(PLP)1820-6, TSOT-23-6
• Oscillator Maximum Duty Cycle (Maxduty)···Typ. 91% (A/B/C Version), Typ. 92% (D/E/F Version)

	BLOCK DIAGRAMS
		R1204xx1xA/D
		(PWM, VFB=0.2V)
	VFB	VIN		LX	VOUT
	Err. Amp.		UVLO
	PWM Comp.
	+
	+	R Q	Driver
	–
	–	S	Control
	vref
	PWM	Oscillator			OVP
	Control	Slope Com-	Current	Current	Thermal
	EN		Limit
		pensation		sense
					Shutdow n
			Soft-start
	Shutdow n
		∑
	delay
	CE
	CE			GND

R1204xx1xB/C/E/F

(B/E:PWM, C/F:PWM/VFM auto switching, VFB=1.0V)

VFB			VIN		LX	VOUT
Err. Amp.	PWM Comp.			UVLO
+		VFM Control
	+
–		R	Q	Driver
	–
vref			S	Control
Soft-start		Oscillator				OVP
		Slope Com-		Current	Current	Thermal
		pensation		Limit	sense	Shutdow n
			∑
CE
CE					GND

	Blue Line : only R1204xx1xC/F
SELECTION GUIDES	TYPICAL APPLICATIONS

Halogen Free	Package	Q'ty per Reel	Part No.
	DFN(PLP)1820-6	5,000 pcs	R1204K	.x.		12		.		-TR
	TSOT-23-6	3,000 pcs	R1204N		.x.		13		.		-TR-FE

.x. : Specify the OVP voltage.

(1) OVP : 23V, (2) OVP : 33V, (3) OVP : 42V

. : Specify the control, feedback voltage and oscillator frequency.

			V	FB	=0.2V					V =1.0V
										FB
	A	PWM, 1MHz					B		PWM, 1MHz
			PWM, 750kHz							PWM/VFM auto switching, 1MHz
	D						C
									PWM, 750kHz
							E
								PWM/VFM auto switching, 750kHz
							F

R1204xx1xA/D			R1204xx1xB/C/E/F
VIN = 2.3V to 5.5V			VIN = 2.3V to 5.5V
L1	D1		L1	D1
C1		C2	C1

VIN	LX	VLED =	VIN	LX
	VOUT	VIN -VFB to	CE	VOUT
CE		VOVP1MIN-3V			C3	C2
GND	VFB			R2	R3
			GND	VFB
		R1
				R1

L1: 10μH(A) or 22μH(D)	L1: 10μH(B/C) or 22μH(E/F),
C1: 1μF, C2: 1μF, R1: 10Ω	C1:	1μF, C2: 1μF, C3: 10pF,
	R1:	10kΩ, R2: 240kΩ, R3: 0Ω

	PACKAGES (Top View)		TYPICAL CHARACTERISTIC

DFN(PLP)1820-6			TSOT-23-6
6	5	4	6	5	4
1	2	3	1	2	3

1	VOUT				4	VIN				1	LX				4	CE
2	LX				5	CE				2	GND				5	VOUT
3	GND				6	VFB				3	VFB				6	VIN

) The tab is substrate level (GND).

Efficiency vs. LED Output Current	L=22μH (VLF302512MT220)
R1204xx1xD 10 LEDs	R1204xx1xF VOUT=31V

	100
	95		Vin= 3.2 V		Vin= 3.6 V
[%]	90		Vin= 4.2 V		Vin= 5 V
	85
Efficiency
	80
	75
	70
	65
	60
	0	5	10	15	20	25	30	35
			Output Current [mA]

	100
	95							Vin= 3.2 V
[%]	90							Vin= 3.6 V
	85							Vin= 5 V
Efficiency
	80
	75
	70
	65
	60
	0	10	20	30	40	50	60	70	80	90
				Output Current [mA]

APPLICATIONS

• OLED power supply for hand-held equipment • White LED backlight for hand-held equipment

No.EK-284-120522

Step-up DC/DC Converter

R1204x Series	Step-up DC/DC Converter

PWM/VFM Step-up DC/DC Converter for White LED / PMOLED and General Use

R1204x Version Lineup

Product Name

R1204xx1xA/D

Application

White LED (Serial drive)

VFB Voltage

0.2V

Comment

LED Current setting

The LED current (ILED) when a ”H” signal is applied to the

CE pin (Duty=100%) can be determined by the value of

feedback resistor (R1).

ILED=0.2 / R1

LED Dimming Control

The LED brightness can be controlled by inputting the

PWM signal to the CE pin. The current of LEDs when

High-Duty of the CE input is ”Hduty” reaches the value

as in next formula.

ILED=Hduty × VFB / R1

The frequency of the PWM signal is using the range

between 200Hz to 300kHz. When controlling the LED

brightness by the PWM signal of 20kHz or less, the

increasing or decreasing of the inductor current might

be make a sounds in the hearable sound wave area. In

that case, please use the PWM signal in the high

frequency area.

Soft-Start Time

Unless otherwise VOUT is beyond the threshold (Vf x

number of LED lights), current will not flow through LEDs,

as a result, VFB voltage will not increase. The IC increases

VOUT by controlling the output of error amplifier to “H” and

turning the Lx switch on and off for a certain period of time

(until the current flow). At the mean time, the inrush

current is controlled by gradually increasing the current

limit. If VOUT is over the threshold (the current flows), the IC

controls the soft-start function by gradually increasing the

reference voltage of error amplifier.

R1204xx1xB/C/E/F

PMOLED, General Use

1.0V

The Method of Output Voltage Setting

Output Voltage= (R1+ R2) / R1

The total value of R1 and R2 should be equal or less than 300kΩ.

Voltage rating of capacitor (C2) is recommended to use 1.5 times or more the output setting voltage.

Soft-Start Time

The IC controls the soft-start function by gradually increasing the reference voltage of error amplifier. Soft-start begins when the output voltage of error amplifier is 0V and ends when it reaches the constant voltage.

The soft start time is set to Typ. 10ms within the IC.

The currently available information as of May 2012 is provided in this New Product News.						EK-284-120522