BD9361GUL Datasheet, PDF (20/27 Pages) Rohm – 6ch Internal Power MOSFET System Switching Regulator + 1ch LDO

BD9361GUL
●Block explanation
1. SCP, Timer Latch
It is a timer latch type of short-circuit protection circuit.
For CH6, the error AMP output voltage is monitored, and detected when the feedback voltage deviates from control,
for CH1～5, it is detected when the voltage of INV terminal becomes lower than 60%, and in 21ms the latch circuit
operates and the outputs of all the channels are fixed at OFF.
In order to reset the latch circuit, please turn off all the STB terminals before turning them on once again or turning
power supply on once again.
2. U.V.L.O
It is a circuit to prevent malfunction at low voltage.
It is to prevent malfunction of internal circuit at the time of rising or dropping to a lower value of power supply voltage.
If the voltage of VCCOUT terminal becomes lower than 2.3V, or the voltage of HX2BAT terminal becomes lower than
2.1V, then the output of each DC/DC converter is reset to OFF, and SCP’s timer latch & soft start circuit are reset. In
order to cancel UVLO of VCCOUT, it is necessary to set VCCOUT more than 2.5V. And in order to cancel UVLO of
HX2BAT, it is necessary to set HX2BAT more than 2.2V.
3. OSC
It is an oscillation circuit the frequency of which is fixed by a built-in CR.
The operating frequencies of CH3, 4, 5 are set at 2MHz, and the operating frequencies of CH1, 2, 6 are set at 1MHz.
4. ERRAMP 1～6
It is an error amplifier to detect output signal and output PWM control signal.
The reference voltages of ERRAMP (Error Amplifier) of CH1～4 are internally set at 0.6V, and the reference
Voltages of ERRAMP (Error Amplifier) of CH5 are set at 0.8V and the reference voltages of ERRAMP (Error Amplifier)
of CH6 are set at 0.4V.
In addition, each CH incorporates a built-in element for phase compensation.
5. Current mode control block
CH1, 3～6 adopt the PWM method based on current mode.
For a current- mode DC/DC converter, FET at the main side of synchronous rectification is turned on when detecting
the clock edge, and turned off by detecting the peak current by means of the current comparator.
6. Cross Control
DUTY controller for CH2 cross converter. It have PWM comparator that compare 1MHz SLOPE and ERROR AMP
output and logic circuit for control 4 FET ON/OFF switching.. LX21 MAX ON DUTY is 100%, LX21 MAX ON DUTY is
92%.
7. Back gate Control
PchFET backgate selector controller in CH1.
PchFET have body Di between backgate and source,drain ordinary. This circuit intercept CH1 step up output voltage
by cutting body Di line at STB OFF and control soft start .CH1 softstart output voltage from 0V like a slope.
8. Nch DRIVER , Pch DRIVER
Internal Nch, Pch FET driver CMOS inverter type output circuit.
9. ON/OFF LOGIC
It is the voltage applied to STB terminal and can control the ON/OFF of CH1～CH4.
If the voltage more than 1.5V is applied, then it becomes ON, but if open or 0V is applied, then it becomes off,
furthermore, it all the channels are turned off, then the whole IC will be in standby state. In addition, STB1234
terminals contain respectively a built-in pull-down resistor of about 400kΩ.
10. SOFT START
It is a circuit to apply the soft start to the output voltage of DC/DC converter and prevent the rush current at the
start-up. Soft start time varies with the channels.
a. CH1
b. CH3,4
c. CH2,5
d. CH6
・・・
reach the target voltage in 3.0ms.
・・・
reach the target voltage in 2.1ms.
・・・
reach the target voltage in 4.2ms.
・・・
reach the target voltage in 8.2ms.
11. OVP COMP6
In CH6, When LED is OPEN, INV6 become L and output voltage increase suddenly. If this condition continue,Lx6
voltage increase and exceed break down voltage. CH6 have Over voltage protection (OVP).When VOUT6 pin is
inputted over 28Vtyp,OVP stop CH6 function..OVP latch CH6 function and reset by All STB=L
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20
TSZ22111・14・001
TSZ02201-0Q2Q0A400010-1-2
2011.12.22 Rev.001