R1272S Series
34 V Input Synchronous Step-down DC / DC Controller
NO.EA-351-170929
OUTLINE
The R1272S is a step-down DC/DC controller which can generate an output voltage of 0.7 V to 5.3 V by driving
external high- / low-side NMOSs. By the adoption of a unique current mode PWM architecture without an
external current sense resistor, the R1272S can make up a stable DC/DC converter with high-efficiency even
if adding low Ron MOSFETs and a low DCR inductor externally. And, by the frequency characteristics
optimization with using external phase compensation capacitor, the R1272S can achieve a high-speed
response to variations of input voltage and load current. The user-settable oscillation frequency is adjustable
over a range of 250 kHz to 1 MHz
(1)
by external resistors, and also can be synchronized to an external clock.
Output Voltage Control Methods have three operating modes: Forced PWM mode, PLL_PWM mode, and
PWM/VFM Auto-switching mode. These modes are selectable according to conditions of the MODE pin.
Especially, the PWM/VFM Auto-switching mode can improve efficiency under light load conditions.
The R1272S can minimize the output voltage drop caused by an input voltage drop at cranking, with reducing
the operating frequency (the lowest possible limit is a quarter of the frequency) so that the off-duty is reduced.
Protection functions include a current limit function, an UVLO (Under Voltage Lock Out) function, an OVP (Over
Voltage Protection) function, a soft-start function, a low-inductor current shutdown function, and so on. Also, a
power good function provide the status of output with using a power good (PGOOD) pin.
For EMI reduction, SSCG (Spread-Spectrum Clock Generator) for diffused oscillation frequency at the PWM
operation is optionally available. The R1272S is available in HSOP-18 package.
FEATURES
● Operating Voltage (Maximum Rating) ······················· 4.0 V to 34 V (36 V)
● Operating Temperature Range ································ -40°C ≤ Ta ≤ 105°C
(Usable in high-temperature environment)
● Start-up Voltage ··················································· 4.5 V
● Output Voltage ················· ··································· 0.7 V to 5.3 V
● Feedback Voltage Tolerance ················· ················· 0.64 V ± 1%
● Consumption Current at No Load (at VFM mode) ········ Typ.15 µA
● Adjustable Oscillation Frequency
(1)
········ ·················· 250 kHz to 1 MHz
● Synchronizable Clock Frequency
(1)
··························· 250 kHz to 1 MHz
● Spreading Rate for SSCG ······································ Typ. ±3.6%
● Minimum On-Time ··· ············································ Typ.100 ns
● Minimum Off-Time ················································ Typ.120 ns (at regulation mode)
At dropout, actual minimum off-time is reduced.
● Adjustable Soft-start Time
(2)
···································· Typ.500 µs
● Pre-bias Start-up
● Anti-phase Clock Output
● Thermal Shutdown Function ··································· Tj = 160ºC (Typ.)
The adjustable oscillation frequency range becomes 250 kHz ≤ f
OSC
≤ 600 kHz when 0.7 V ≤ V
OUT
< 1.35V.
500 µs (Typ.) as a lower limit with using an external capacitor. Otherwise, available the tracking function through the
application of an external voltage.
(2)
(1)
1
R1272S
NO.EA-351-170929
● Under Voltage Lockout (UVLO) Function········· ·········· Typ. 3.3 V
● Over Voltage Detection (OVD) Function ···················· FB pin voltage (V
FB
) + 10% (Typ.)
Detection/Release Hysteresis ································· FB pin voltage (V
FB
) x 3% (Typ.)
● Under Voltage Detection (UVD) Function ···················
Detection/Release Hysteresis ·································
● Over-current Protection··········································
● Selectable Current Limit Threshold ···························
● Power Good Output ··············································
● Package ·····························································
FB pin voltage (V
FB
) - 10% (Typ.)
FB pin voltage (V
FB
) x 3% (Typ.)
Hiccup-mode / Latch mode
50 mV / 70 mV / 100 mV
NMOS Open-drain Output
HSOP-18
APPLICATIONS
● Power source for digital home appliances such as digital TV, DVD players.
● Power source for office equipment such as printers and fax machines.
● Power source for 5V PSU or 2-cell or more Li-ion battery powered communication equipment, cameras,
video instruments such as VCRs, camcorders.
● Power source for high voltage battery-powered equipment.
SELECTION GUIDE
The function and setting for the ICs are selectable at the user’s request.
Product Name
R1272SxxyA-E2-FE
Package
HSOP-18
Quantity per Reel
1,000
Pb Free
Yes
Halogen Free
Yes
xx : Select the combination of processing and function.
xx
Over Current Protection
SSCG
00
Non-latch type hiccup mode
Disable
01
Latch mode
Disable
03
Latch mode
Enable
If required a version with SSCG function, please contact our sales offices.
y : Select the current limit threshold voltage.
y
1
2
3
Set Voltage for Current
Limit Threshold (Typ.)
50 mV
70 mV
100 mV
2
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