RP901K SERIES
Synchronous Step-down DC/DC Converter with VD and VR
NO.EA-156-121225
OUTLINE
The RP901xxxx is a CMOS-based current mode PWM control synchronous step-down DC/DC converter with a
voltage detector (VD) and an LDO regulator (VR).
Each of Step-down DC/DC converters is composed of an oscillator, a voltage reference unit, an error amplifier, a
switching control circuit, a soft-start circuit, a protection circuit, a UVLO circuit, a switching transistor. Due to the
switching elements are built in and synchronous control, a high efficiency step-down DC/DC converter can be
made with an inductor and capacitors. To realize high efficiency at light load, automatic PWM/VFM alternative
mode can be selected other than the PWM fixed control mode.
As protection circuits, a current limit circuit which limits Lx peak current cycle by cycle and a hiccup mode
protection circuit which works if the load current over the limit continues for a certain time are built in. The output
voltage can be preset with 0.05V step in the factory due to the built-in feed back resistance, and the tolerance is
±2%. Since the package is DFN (PLP) 2527-10, high density mounting on board is possible.
Built-in LDO regulator (VR) is composed of a voltage reference unit, a voltage detecting resistor-network, an
error amplifier, a short current limit circuit, and a driver transistor. After the soft-start time of the DC/DC converter
is over and a specified delay time, LDO starts up. The sequence function is fixed internally .
Built-in voltage detector (VD) supervises the input voltage or the output of the VR (The reset function works for
UVLO and over-current of the DC/DC converter). The option is preset in the factory. The output type is N-channel
open drain. The released delay time is built-in, typ.50ms.
If the junction temperature of the IC is over the limit, the system is reset by the built-in thermal shut-down circuit.
*1)
*2)
A version: As soon as the load current is over the limit, the system restarts by the protection.
C, D versions: No sequence function
*2
*1
FEATURES
•
Input Voltage Range ················································· 4.5V to 5.5V
•
Supply Current·························································· Typ. 460µA (at PWM mode)
Typ. 170µA (at light load applied to B, C, D versions)
Step-down DC/DC Converter
•
Output Voltage Range ·············································· 1.2V to 1.8V, preset is possible by user’s request
•
Output Voltage Tolerance ········································· ±2%
•
Oscillator Frequency················································· Typ. 1.2MHz
•
Built-in driver ON resistance····································· Typ. P-channel 0.25Ω, N-channel 0.25Ω (at V
IN
=5V)
•
Soft-start function······················································ Typ. 1ms
•
Lx peak current limit function···································· Typ. 1.4A (D version: 1.5A)
•
Output Current·························································· Min. 800mA (D version: 900mA)
•
Protection Delay Time ·············································· Typ. 0.1ms (applied to B, C, D versions)
•
UVLO function ·························································· Typ. 3.5V
•
Chip enable function················································· ”H” active
Ver. 1.0
1
RP901K
LDO Regulator
•
Output Voltage Range ·············································· 2.5V to 3.3V, preset is possible by user’s request
•
Output Voltage Tolerance ········································· ±1.0%
•
Output Current ·························································· Min. 600mA
•
Start-up delay time···················································· Typ. 2ms (applied to A, B versions)
•
Auto-Discharge function at turning off ······················ Discharge resistance Typ.50Ω (at V
IN
=5V)
VD
•
Voltage Detector Threshold Range ·························· 2.0V to 3.0V, preset is possible by user’s request
(A version: VR output voltage is supervised),
3.0V to 5.0V, preset is possible by user’s request
(B, C, D versions: Input voltage is supervised）
•
Released Delay Time················································ Typ.50ms
•
Thermal shutdown circuit·········································· Detecting Temperature: Typ. 165°C,
Released temperature: Typ. 110°C
•
Package···································································· DFN(PLP)2527-10
•
External Components ··············································· C
IN
=10.0µF, C
OUT1
=10.0µF, L=4.7µH (DC/DC),
C
OUT2
=2.2µF(VR)
APPLICATION
•
Optical Disk Equipment
Ver. 2.5
2
RP901K
BLOCK DIAGRAMS
A version
PVDD
CE
CHIP
ENABLE
RAMP
COMPENSATION
CURRENT
FEEDBACK
OSCILLATOR
CURRENT
PROTECTION
SWITCHING
CONTROL
UVLO
L
X
VREF
PWM
SOFT
START
V
OUT1
PGND
AVDD
VREF
AGND
V
OUT2
CE
CURRENT
PROTECTION
VREF
V
DOUT
DELAY CIRCUIT
B/C/D version
PVDD
CE
CHIP
ENABLE
RAMP
COMPENSATION
CURRENT
FEEDBACK
OSCILLATOR
CURRENT
PROTECTION
SWITCHING
CONTROL
UVLO
L
X
VREF
PWM／VFM
SOFT
START
V
OUT1
PGND
AVDD
VREF
DELAY CIRCUIT
AGND
V
OUT2
CE
CURRENT
PROTECTION
VREF
V
DOUT
Ver. 2.5
2
RP901K
SELECTION GUIDE
In the RP901 series, the output voltage combination and function can be designated.
The selection can be made by the alphanumeric serial number as the next example.
Product Code
RP901Kxxx∗-TR
Package
DFN(PLP)2527-10
Units/ 1 reel
5,000pcs
Pb free
Yes
Halogen free
Yes
xxx: Serial number to describe the voltage combination of DC/DC converter, voltage regulator, and
voltage detector.
∗:
Function version
A version: DC/DC control type is PWM-fixed, without protection delay time, output current Min.
800mA, VR has start-up delay time to make a sequence. VD supervises the output of VR (Reset is
output at UVLO and over current of DC/DC)
B version: DC/DC control type is PWM/VFM automatic mode shift, with protection delay time,
output current Min. 800mA, VR has start-up delay time to make a sequence. VD supervises the input
voltage.
C version: DC/DC control type is PWM/VFM automatic mode shift, with protection delay time,
output current Min. 800mA, VR: without delay time to make a sequence, VD supervises the input
voltage.
D version: DC/DC control type is PWM/VFM automatic mode shift, with protection delay time,
output current Min. 900mA, VR: without delay time to make a sequence, VD supervises the input
voltage.
PIN CONFIGURATION
DFN(PLP)2527-10
Mark Side
Bottom Side
9
10
10
9
8
7
6
6
7
8
1
2
3
4
5
5
4
3
2
1
Steam via
Ver. 2.5
2
RP901K
PIN DESCRIPTIONS
Pin No.
1
2
3
4
5
6
7
8
9
10
Symbol
CE
V
DOUT
AGND
PGND
L
X
PVDD
NC
V
OUT1
AVDD
V
OUT2
Chip Enable Pin (”H” active)
VD Output Pin (N-channel open drain output)
Analog Ground Pin
Power Ground Pin
DC/DC Switching Pin
Power Supply Input Pin
No connection
DC/DC Output Pin
Analog Power Supply Input Pin
VR Output Pin
Description
The backside of the package tab is connected to the substrate of the IC (GND). Connect to GND pin
(Recommendation), or solder the tab and left open electrically.
Make short 3pin and 4pin, and make short 6pin and 9pin.
ABSOLUTE MAXIMUM RATINGS
(GND=0V)
Symbol
V
IN
V
CE
V
LX
V
OUT1
V
OUT2
V
DOUT
P
D
Ta
Tstg
*
Item
PVDD Pin Voltage
AVDD Pin Voltage
CE Pin Voltage
L
X
Pin Voltage
V
OUT
1 Pin Voltage
V
OUT
2 Pin Voltage
V
DOUT
Pin Voltage
Power Dissipation*
Operating
Temperature
Storage Temperature
(1)
(2)
Rating
6.5
-0.3 to 6.5
-0.3 to V
IN
+ 0.3
-0.3 to V
IN
+ 0.3
-0.3 to V
IN
+ 0.3
-0.3 to 6.5
1750 (Ta=25°C, Tjmax=150°C)
1138 (Ta=25°C, Tjmax=150°C)
-40 to +85
-55 to +125
Unit
V
V
V
V
V
V
mW
°C
°C
For more information about Power Dissipation and Standard Land Pattern, refer to
PACKAGE INFORMATION.
ABSOLUTE MAXIMUM RATINGS
Electronic and mechanical stress momentarily exceeded absolute maximum ratings may cause the permanent
damages and may degrade the life time and safety for both device and system using the device in the field. The
functional operation at or over these absolute maximum ratings is not assured.
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.
Ver. 2.5
2
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