BU90002GWZ Datasheet, PDF (2/24 Pages) Rohm – Step-down Switching regulators with Built-in Power MOSFET

BU9000xGWZ series
●Block Diagram(s)
TSD
FB
VOUT B3
MODE
L ：　PWM/PFM MODE
H ：　PWM MODE
B1
UVLO
PWM/PFM
control
EN
VIN
A1
Datasheet
2.3～5.5V
-
Switching
+
Control Logic
and
ERROR COMP
Gate Driver
VREF
1.5～0.47uH
B2
VOUT
4.7uF
LX
EN
H ：　ON
A2
L ：　OFF
SHUTDOWN
Frequency
control
GND
A3
Figure 3. Block Diagram(s)
●Description of Block(s)
The BU9000xGWZ are a synchronous step-down DC/DC converter that achieves fast transient response from light load to
heavy load by hysteretic PWM control system and current constant PFM control system.
○PWM control
BU9000xGWZ operates by hysteretic PWM control. This scheme ensures fast switching, high efficiency, and fast transient
response.
When the output voltage is below the VREF voltage, the error comparator output is low to high and turning on P-channel
MOSFET until above the VREF voltage and minimum on time.
○PFM control
At light load the regulator and MODE=low, the regulator operates with reduced switching frequency and improves the
efficiency.During PFM operation, the output voltage slightly higher than typical output voltage.
PFM (constant current)Threshold. turn off Pch FET
PFM Threshold. turn on PFET
PFM Mode at Light Load
output PWM mode voltage
PWM Mode at Moderate to Heavy Loads
Figure 4. Operation of PFM mode and PWM mode
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TSZ22111・15・001
2/21
TSZ02201-0F2F0AG00010-1-2
04.Jul.2012 Rev.001