BU90054GWZ Datasheet, PDF (2/18 Pages) Rohm – Fast transient response

BU90054GWZ
●Block Diagram(s)
FB
VOUT B3
TSD
L ：　PWM/PFM MODE
MODE
H ：　PWM MODE
B1
UVLO
PWM/PFM
control
VIN
A1
EN
2.3～5.5V
-
+
ERROR COMP
VREF
Switching
Control Logic
and
Gate Driver
1.5～0.47uH
B2
VOUT
LX
4.7uF
EN
H ：　ON _A2
L ：　OFF
SHUTDOWN
Frequency
control
GND
A3
Figure 3. Block Diagram(s)
●Description of Block(s)
The BU90054GWZ 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
BU90054GWZ 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 Pch FET
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
2/15
TSZ02201-0F1F0AG00060-1-2
8.Dec.2014 Rev.002