R1287x Series
PWM/ VFM, Dual-channel Step-up/ Inverting DC/DC Converter
with Synchronous Rectifier for LCD
NO.EA-325-180907
OUTLINE
The R1287x is a PWM/ VFM dual-channel step-up/ inverting DC/DC converter with synchronous rectifier for
LCD. The step-up DC/DC converter (CH1) generates a 4.5 V to 5.8 V boosted output voltage and the inverting
DC/DC converter (CH2) generates a −4.5 V to −6.0 V inverting output voltage.
Internally, the R1287x consists of an oscillator circuit, PWM control circuits, a reference voltage unit, error
amplifiers, soft-start circuits, a L
X
peak current limit circuit, short protection circuits, thermal shutdown circuit,
an under voltage lockout circuit (UVLO), a NMOS transistor driver and a synchronous PMOS transistor driver
for CH1, and a PMOS transistor driver and a synchronous NMOS transistor driver for CH2.
The R1287x is employing synchronous rectification for improving the efficiency of rectification by replacing
diodes with built-in switching transistors. Using synchronous rectification not only increases circuit performance
but also allows a design to reduce parts count.
The R1287x provides the PWM control or the PWM/VFM auto switching control. The PWM control switches at
fixed frequency rate in low output current in order to reduce noise. Likewise, the PWM/VFM auto switching
control automatically switches from PWM mode to VFM mode in low output current in order to achieve high
efficiency. RICOH’s unique control method can suppress a ripple voltage in the VFM mode, thus the R1287x
can achieve both low ripple voltage at light load and high efficiency.
Both CH1 and CH2 can independently control the ON/ OFF control and freely set the starting sequence and
shutdown sequence. Both CH1 and CH2 own an auto-discharge function which actively discharges the output
voltage to ground when the device is placed in shutdown mode.
The R1287x is offered in a 12-pin WLCSP-12-P1 package and a 12-pin DFN3030-12 package.
FEATURES
Operating Voltage Range ·············································· 2.5 V to 5.5 V
[Step-up DC/DC Converter (CH1)]
Selectable Step-up Output Voltage (V
OUTP
) ······················ R1287xxxxy: 4.5 V to 5.8 V (0.1 V Step)
Step-up Output Voltage (Externally adjustable) ················· R1287x001y: 4.5 V to 5.8 V
Maximum Output Current (Dependent on inductance) ········· R1287xxxxB/D/F/H: 200 mA,
R1287xxxxC/G: 100 mA
[Inverting DC/DC Converter (CH2)]
Selectable Inverting Output Voltage (V
OUTN
) ····················· R1287xxxxy: −4.5 V to −5.8 V (0.1 V Step)
Inverting Output Voltage (externally adjustable) ················· R1287x001y: −4.5 V to −6.0 V
Maximum Output Current (dependent on inductance) ·········· R1287xxxxB/D/F/H: 200 mA,
R1287xxxxC/G: 100 mA
1
R1287x
NO.EA-325-180907
[Controller]
ON/ OFF Control: Operates CH1/ CH2 separately by the EN1/ EN2 pin.
Auto-discharge Function: Discharges the output voltage to GND within a short time in shutdown mode.
Latch-type Short Circuit Protection: Short-circuiting of either one of CH1 or CH2 activates this circuit.
Maximum Duty Cycle
L
X
Peak Current Limit Function
Undervoltage Lockout (UVLO) Threshold ························ Typ. 2.25 V
Thermal Shutdown Temperature ···································· Typ. 150°C
Oscillator Frequency ··················································· R1287xxxxB/D/F/H:1 MHz,
R1287xxxxC/G: 300 kHz
Package ··································································· WLCSP-12-P1, DFN3030-12
APPLICATIONS
Power source for hand-held equipment
Power source for LCD
2
R1287x
NO.EA-325-180907
SELECTION GUIDE
The output voltage types are user-selectable options that can be selected from either fixed output voltage type
or adjustable output voltage type. With the fixed output voltage type, the combination of a CH1 output voltage
and a CH2 output voltage can be selected. The combination of an oscillator frequency, a power controlling
method, and a discharge current can also be selected.
Selection Guide
Product Name
R1287Zxxxy-E2-F
R1287Lxxxy-TR
Package
WLCSP-12-P1
DFN3030-12
Quantity per Reel
4,000 pcs
3,000 pcs
Pb Free
Yes
Yes
Halogen Free
Yes
Yes
xxx: Specify the set output voltage (V
SET
).
001: Adjustable Output Voltage Type, The output voltage is adjustable using external resistors.
002 to 009: Fixed Output Voltage Type
CH1 Output Voltage (V
OUTP
): selectable from +4.5 V to +5.8 V by 0.1 V step
(1)
CH2 Output Voltage (V
OUTN
): selectable from −4.5 V to −5.8 V by 0.1 V step
(1)
Notes: Refer to
Output Voltage for All Combinations of V
OUTP
and V
OUTN
.
y: Specify the oscillator frequency, the power controlling method, and the discharge current.
(B) 1 MHz, PWM/ VFM Auto Switching Control, discharge current 0.06 mA
(C) 300 kHz, PWM Control, discharge current 0.06 mA
(D) 1 MHz, PWM Control, discharge current 0.06 mA
(F) 1 MHz, PWM/ VFM Auto Switching Control, discharge current 0.4 mA
(2)
(G) 300 kHz, PWM Control, discharge current 0.4 mA
(2)
(H) 1 MHz, PWM Control, discharge current 0.4 mA
(3)
Output Voltage for All Combinations of V
OUTP
and V
OUTN
V
SET
Code No. (xxx)
CH1 Output Voltage (V
OUTP
)
001
Adjustable using external resistors
002
5.0
003
5.4
004
5.75
005
5.6
006
4.5
007
5.8
008
5.5
(4)
009
5.1
(1)
(2)
(3)
(4)
CH2 Output Voltage (V
OUTN
)
Adjustable using external resistors
−5.0
−5.4
−5.75
−5.6
−4.5
−5.8
−5.5
−5.1
0.05 V step is also available as a custom code
F/G versions are only available for R1287Z
H version is only available for R1287Z and R1287L002H, R1287L003H, R1287L007H
V
SET
Code No.009 is only available for R1287Z
3
R1287x
NO.EA-325-180907
BLOCK DIAGRAMS
R1287xxxxy Block Diagram (Fixed Output Voltage Type)
4
R1287x
NO.EA-325-180907
R1287x001y Block Diagram (Adjustable Output Voltage Type)
5
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