Document
R1204x Series
Step-up DC/DC Converter with Shutdown Function
No. EA-284-180511
OUTLINE
The R1204x is a low supply current PWM step-up DC/DC converter. Internally, a single IC consists of an NMOS FET, an oscillator, a PWM comparator, a voltage reference unit, an error amplifier, a current limit circuit, an under voltage lockout circuit (UVLO), an over-voltage protection circuit (OVP), a soft-start circuit, a maximum duty cycle limit circuit, and a thermal shutdown protection circuit. By simply using an inductor, a resistor, capacitors and a diode as external components, a high-efficiency step-up DC/DC converter can be easily configured. As protection functions, the IC contains a thermal shutdown protection circuit, a current limit circuit, an OVP circuit, and an UVLO circuit. A thermal shutdown circuit detects overheating of the ICs and stops the operation to protect it from damage. A current limit circuit limits the peak current of Lx, and an OVP circuit detects the over voltage of output, and an UVLO circuit detects the low input voltage. The R1204x provides the R1204xxxA/D/G/H versions, which are optimized for serial driving of white LEDs with constant current, and the R1204xxxB/C/E/F versions, which are optimized for constant voltage driving. Among the R1204xxxB/C/E/F versions, only the R1204xxxC/F versions are equipped with PWM/VFM auto-switching controls. The LED current can be determined by the value of current setting resistor. The brightness of the LEDs can be quickly adjusted by applying a PWM signal (200 Hz to 300 kHz) to the CE pin. The R1204x is available in DFN(PLP)1820-6 and TSOT-23-6 packages.
FEATURES
Input Voltage Range..........................................2.3 V to 5.5 V Supply Current ..................................................Typ. 800 µA Standby Current ................................................Max. 5 µA Feedback Voltage .............................................0.2 V ±10 mV (R1204xxxxA/D)
0.4 V ±10 mV (R1204xxxxG/H) V ±15 mV (R1204xxxxB/C/E/F) Lx Current Limit Function..................................Min. 700 mA Over Voltage Protection ....................................23 V, 33 V, 42 V (±1.5 V) Oscillator Frequency .........................................Typ. 1.0 MHz (R1204xxxxA/B/C/G)
Typ. 750 kHz (R1204xxxxD/E/F/H) Maximum Duty Cycle ........................................Min. 91% (R1204xxxxA/B/C/G)
Min. 92% (R1204xxxxD/E/F/H) FET ON Resistance ..........................................Typ. 0.8 Ω UVLO Function Thermal Protection Function LED Dimming Control for R1204xxxxA/D .........by external PWM signal (200 Hz to 300 kHz frequency) Packages ..........................................................DFN(PLP)1820-6, TSOT-23-6 Recommended Bypass Capacitor ....................1.0 µF
APPLICATIONS
Constant voltage power source for hand-held equipment OLED power supply for hand-held equipment White LED driver for hand-held equipment
1
R1204x
No. EA-284-180511
SELECTION GUIDE
The package type, the OVP detector threshold, the feedback voltage and the PWM//VFM auto-switching control are user- selectable options as described below.
Selection Guide Product Name
R1204Kxy2z-TR R1204Nxy3z-TR-FE
Package DFN(PLP)1820-6
TSOT-23-6
Quantity per Reel 5,000 pcs 3,000 pcs
Pb Free Yes Yes
Halogen Free Yes Yes
x: OVP Detector Threshold 1: 23 V 2: 33 V 3: 42 V
y: Current Limit 1: Typ. 900 mA
z: Feedback Voltage, Oscillator Frequency, PWM/VFM Auto-Switching Control
z
Feedback Voltage
Oscillator Frequency
PWM/VFM Auto-Switching Control
A Typ. 0.2 V
No
B Typ. 1 V Typ. 1 MHz
No
C Typ. 1 V
Yes
D Typ. 0.2 V
No
E Typ. 1 V
Typ. 750 kHz
No
F Typ. 1 V
Yes
G Typ. 1 MHz Typ. 0.4 V
H Typ. 750 kHz
No
2
BLOCK DIAGRAMS
VFB
R1204x
No. EA-284-180511
VIN Lx VOUT
Err. Amp. + –
EN
Shutdow n delay
vref Sof t-s tart
CE PWM Control
PWM Comp. + RQ –S
Oscillator
UVLO
Driver Control
OVP
Slope Compensation
Thermal Shutdow n
∑
Current Limit
Current sense
CE
R1204xxxxA/D/G/H Block Diagram
VFB VIN Lx
Err. Amp. + –
vref
Sof t-s tart
PWM Comp. + RQ –S
Oscillator
UVLO
Driver Control
OVP
Slope Compensation
Thermal Shutdow n
∑ Current CE sense
Current Limit
CE GND
R1204xxxxB/E Block Diagram
V OUT
3
R1204x
No. EA-284-180511
VFB VIN Lx
Err. Amp. + –
vref
PWM Comp. VFM Control
+ RQ
–S
UVLO
Driver Control
Oscillator
OVP
Sof t-s tart CE
Slope Compensation
Thermal Shutdow n
∑
Current Limit
Current sense
CE GND
R1204xxxxC/F Block Diagram
V OUT
4
PIN DESCRIPTIONS
Top View
654
Bottom View
456
R1204x
No. EA-284-180511
654 (mark side)
123
321
DFN(PLP)1820-6 Pin Configuration
123
TSOT-23-6 Pin Configuration
DFN(PLP)1820-6 Pin Description
Pin No
Symbol
1 VOUT
2 LX
3 GND
4 VIN
5 CE
6 VFB
Description Output Pin Switching Pin, Open Drain Output Ground Pin Input Pin Chip Enable Pin, Active-high Feedback Pin
The exposed tab is substrate level (GND). I.