RT9986 RICHTEK [Richtek Technology Corporation], RT9986 Datasheet - Page 18

• Manufacturer Part Number: RT9986
• Description: 7-CH DC/DC Converter for DSC
• Manufacturer: RICHTEK [Richtek Technology Corporation]

RT9986
Application Information
The RT9986 is a multiple output power supply system for
digital still cameras and other small handheld devices. It
includes six DC/DC converters as well as one WLED driver,
one RTC LDO, one voltage detector, and one system reset.
The WLED works in either current source mode or step-
up mode.
CH1 : Step-up synchronous current mode DC/DC converter
with internal power MOSFETs and compensation network.
The P-MOSFET body can be controlled to disconnect the
load.
CH2 : Step-up or step-down synchronous current mode
DC/DC converter with internal power MOSFETs and
compensation network. External circuit topology
automatically determines whether CH2 is in step-up or
step-down mode. During step-up mode, the P-MOSFET
body can be controlled to disconnect the load if input
voltage is not higher than the V
CH3 : Step-down synchronous current mode DC/DC
conv erter wit h int ernal power MOSFETs and
compensation network.
CH4 : Step-down synchronous current mode DC/DC
conv erter wit h int ernal power MOSFETs and
compensation network.
CH5 : Step-up synchronous current mode DC/DC converter
with internal power MOSFET and compensation network.
The P-MOSFET body can be controlled to disconnect the
load.
CH6 : Asynchronous inverting current mode DC/DC
converter with internal power MOSFET and compensation
network.
CH7 : A WLED driver operating in either current source
mode or synchronous step-up mode with internal power
MOSFET and compensation network. Operation mode is
determined by LX7 initial voltage The P-MOSFET body in
step-up mode can be controlled to disconnect the load
disconnected.
CH1 to CH4 operate in PWM mode with 2MHz, while
CH5 to CH7 operate in PWM mode with 1MHz switching
frequency.
RTC_LDO : A 3.1V output LDO with low quiescent current
and high output voltage accuracy.
www.richtek.com
18
BAT
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System Reset : Accurate voltage detector for checking
CH2 output voltage status.
Voltage Detector : A general, low quiescent current voltage
detector for monitoring status of a node voltage such as
for RTC_LDO output or others.
CH1 : Synchronous Step-Up DC/DC Converter
CH1 is a synchronous step-up converter which can be
used for motor power. The converter operates at fixed
frequency and PWM current mode. The converter
integrates 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 / Step-Down
Selectable DC/DC Converter
CH2 is a synchronous step-up / step-down auto-select
converter, typically for system I/O power. In either step-
up or step-down, the converter operates in fixed frequency
PWM mode, Continuous Current Mode (CCM), and
Discontinuous Current Mode (DCM) with internal
MOSFETs, compensation network and synchronous
rectifiers for up to 95% efficiency.
Step-Up :
In step-up mode, CH2 also disconnects the load from its
input power node and discharges output node of CH2 when
it is turned off.
Step-Down :
In step-down mode, the CH2 converter can be operated
at 100% maximum duty cycle to extend the input
operating voltage range. When 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
OUT_CH1
OUT_CH2
FB1
FB2
= (1 + R1 / R2) x V
= (1 + R3 / R4) x V
is 0.8V typically.
is 0.8V typically.
FB1
FB2
DS9986-00 May 2011