RT9953 RICHTEK [Richtek Technology Corporation], RT9953 Datasheet - Page 15

• Manufacturer Part Number: RT9953
• Description: 4+1 CH Power Management IC
• Manufacturer: RICHTEK [Richtek Technology Corporation]

Application information
The RT9953 includes the following four DC/DC converters
and one LDO to build a multiple-output power-supply
system.
CH1 : Synchronous Step-Up DC/DC Converter
The CH1 is a synchronous step-up converter for motor or
DSC system I/O power. The converter operates at fixed
frequency and PWM Current Mode. The CH1 converter
integrated internal MOSFETs, compensation network and
synchronous rectifier for up to 95% efficiency.
The output voltage can be set by the following equation :
V
Where V
CH2 : Synchronous Step-Up or Step-Down
Selectable DC/DC Converter
The CH2 is a synchronous step-up/step-down selectable
converter for motor or DSC system I/O power.
Mode setting
The CH2 of RT9953 features flexible Step-up or Step-down
topology setting for either 1 x Li-ion or 2 x AA application
by SEL pin. Please refer to “Electrical Characteristics”
for level of Logic-High or Logic-Low. When the CH2
operates as a Step-up converter, the SEL must be set at
Logic-High. If the CH2 operates at Step-down mode, the
SEL must be set at Logic-Low. In addition, please note
that the logic state can not be changed during operation.
Step-Up :
The converter operates at fixed frequency PWM Mode,
continuous current mode (CCM), and discontinuous current
mode (DCM) with internal MOSFETs, compensation
network and synchronous rectifier for up to 95% efficiency.
DS9953-02 April 2011
OUT_CH1
FB1
= (1+R1/R2) x V
Logic-High
Logic-Low
is 0.8V typically.
SEL
Table 2. CH2 Mode Setting
FB1
CH2 Operating Mode
Step-Down
Step-Up
Step-Down :
The converter operates at fixed frequency PWM mode
and continuous current mode (CCM) with internal
MOSFETs, compensation network and synchronous
rectifier for up to 95% efficiency. The CH2 Step-down
converter can be operating at 100% maximum duty cycle
to extend the input operating voltage range. While the
input voltage is close to the output voltage, the converter
enters low dropout mode.
The output voltage can be set by the following equation :
V
Where V
CH3 and CH4 : Synchronous Step-Down DC/DC
Converter
The converter operates at fixed frequency PWM mode,
CCM and integrated internal MOSFETs and compensation
network. The CH3 and CH4 Step-down converter can be
operating at 100% maximum duty cycle to extend battery
operating voltage range. When the input voltage is close
to the output voltage, the converter could enter low dropout
mode with low output ripple.
The output voltage can be set by the following equation :
V
V
Where V
CH5 : 500mA Low Dropout, Low Noise Linear
Regulator
Like any low-dropout regulator, this CH requires input and
output decoupling capacitors. The CH5 linear regulator
can support 500mA output current when PVDD5 > 2.7V.
The typical current limit is 0.8A. If the output is shorted to
ground, the Under Voltage Protection function will be
triggered to shutdown the IC to prevent the part from
damaging.
The output voltage can be set by the following equation :
V
Where V
OUT_CH2
OUT_CH3
OUT_CH4
OUT_CH5
FB2
FB3
FB5
= (1+R3/R4) x V
= (1+R5/R6) x V
= (1+R7/R8) x V
= (1+R9/R10) x V
is 0.8V typically.
is 0.8V typically.
and V
FB4
is 0.8V typically.
FB2
FB3
FB4
FB5
RT9953
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