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PDF RT9605A Data sheet ( Hoja de datos )
| Número de pieza | RT9605A | |
| Descripción | Triple-Channel Synchronous-Rectified Buck MOSFET Driver | |
| Fabricantes | Richtek Technology Corporation | |
| Logotipo |  |
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Preliminary
RT9605A
Triple-Channel Synchronous-Rectified Buck MOSFET Driver
General Description
The RT9605A is a high frequency, triple-channel
synchronous-rectified buck MOSFET driver specifically
designed to drive six power N-MOSFETs. The part is
promoted to pair with RichTek's multiphase buck PWM
controller family for high-density power supply
implementation. The output drivers of RT9605A can
www.DataSheet4U.com
efficiently switch power MOSFETs at frequency 300kHz
typically. Operating in higher frequency should consider
the thermal dissipation carefully. Each driver of RT9605A
is capable to drive a 3nF load in 30/40ns rising/falling
time with little propagation delay from input transition to
the gate of the power MOSFET. The device implements
bootstrapping on the upper gate with only an external
capacitor and a diode required. This reduces circuit
complexity and allows the use of higher performance, cost
effective N-MOSFETs. All drivers incorporate adaptive
shoot-through protection to prevent upper and lower
MOSFETs from conducting simultaneously and shorting
the input supply. The RT9605A also detects the fault
condition during initial start-up prior to the multi-phase
PWM controller takes control. As a result, the input supply
will latch into the shutdown state. The RT9605A comes
to a small footprint package with VQFN-24L 4x4 package.
Ordering Information
RT9605A
Package Type
QV : VQFN-24L 4x4 (V-Type)
Operating Temperature Range
P : Pb Free with Commercial Standard
G : Green (Halogen Free with Commer-
cial Standard)
Note :
Richtek Pb-free and Green products are :
`RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
`Suitable for use in SnPb or Pb-free soldering processes.
`100% matte tin (Sn) plating.
Features
z Drive Six N-MOSFETs for 3-Phase Buck PWM Control
z Adaptive Shoot-Through Protection
z Support High Switching Frequency
z Fast Output Rise/Fall Time
z Propagation Delay 40ns
z Tri-State Input for Bridge Shutdown
z Upper MOSFET Direct Short Protection
z Small 24-Lead VQFN Package
z RoHS Compliant and 100% Lead (Pb)-Free
Applications
z CPU Core Voltage Supplies on Motherboard
z High Frequency Low Profile DC-DC Converters
z High Current Low Voltage DC-DC Converters
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area, otherwise visit our website for detail.
Pin Configurations
(TOP VIEW)
24 23 22 21 20 19
UGATE1 1
18 GND
BOOT1 2
17 UGATE2
NC 3
PWM1 4
GND
16 BOOT2
15 PVCC3
PWM2 5
GND 6
14 LGATE3
25 13 GND
7 8 9 10 11 12
VQFN-24L 4x4
DS9605A-05 August 2007
All brandname or trademark belong to their owner respectively
www.richtek.com
1
1 page  
Preliminary
RT9605A
Parameter
Symbol
Test Conditions
Min Typ Max Units
Output
UGATE Rise Time
TRUGATE PVCC = 12V, 3nF load
-- 30 -- ns
UGATE Fall Time
TFUGATE PVCC = 12V, 3nF load
-- 40 -- ns
LGATE Rise Time
TRLGATE PVCC = 12V, 3nF load
-- 30 -- ns
LGATE Fall Time
TFLGATE PVCC = 12V, 3nF load
-- 30 -- ns
UGATE Turn-Off Propagation Delay TPDUGATE PVCC = 12V, 3nF load
-- 40 -- ns
LGATE Turn-Off Propagation Delay TPDLGATE PVCC = 12V, 3nF load
-- 35 -- ns
Shutdown Window
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1.0 -- 4.3 V
Note 1. Stresses listed as the above “Absolute Maximum Ratings” may cause permanent damage to the device. These are for
stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the
operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended
periods may remain possibility to affect device reliability.
Note 2. Devices are ESD sensitive. Handling precaution recommended.
Note 3. The device is not guaranteed to function outside its operating conditions.
Note 4. θJA is measured in the natural convection at TA = 25°C on a low effective thermal conductivity test board of
JEDEC 51-3 thermal measurement standard.
DS9605A-05 August 2007
All brandname or trademark belong to their owner respectively
www.richtek.com
5
5 Page 
Preliminary
RT9605A
In practice, a low value capacitor CB will lead the over-
charging that could damage the IC. Therefore to minimize
the risk of overcharging and reducing the ripple on VCB,
the bootstrap capacitor should not be smaller than 0.1μF,
and the larger the better. In general design, using 1μF can
provide better performance. At least one low-ESR capacitor
should be used to provide good local de-coupling. Here,
to adopt either a ceramic or tantalum capacitor is suitable.
Power Dissipation
www.DataShFeoert4Un.ocot mexceeding the maximum allowable power
dissipation to drive the IC beyond the maximum
recommended operating junction temperature of 125°C,
it is necessary to calculate power dissipation appro-
priately. This dissipation is a function of switching
frequency and total gate charge of the selected MOSFET.
Figure 4 shows the power dissipation test circuit. CL and
CU are the UGATE and LGATE load capacitors,
respectively. The bootstrap capacitor value is 1μF.
+12V
10
1uF
PWM
1N4148
1uF
CBOOTx
BOOTX
VDD UGATEX
RT9605A
PHASEX
PWMX LGATEX
GND
+12V
2N7002
CU
3nF
2N7002
CL
3nF
20
The method to improve the thermal transfer is to increase
the PC board copper area around the RT9605A firstly.
Then, adding a ground pad under IC to transfer the heat to
the peripheral of the board.
Power Dissipation vs. Frequency
1000
900
CU=CL=3nF
800
700
600
500
400 CU=CL=2nF
300
200 CU=CL=1nF
100
0
0 200 400 600 800 1000
Frequency (kHz)
Figure 5. Power Dissipation vs. Frequency
Over-Voltage Protection Function at Power-On
An unique feature of the RT9605A is the addition of over-
voltage protection in the event of upper MOSFET direct
shorted before power-on. The RT9605A detects the fault
condition during initial start-up, the internal power-on OVP
sense circuitry will rapidly drive the low side MOSFET on
before the multi-phase PWM controller takes control.
Figure 6 shows the measured waveforms with the high
side MOSFET directly shorted to 12V.
Figure 4. Test Circuit (One Phase is Shown)
Figure 5 shows the power dissipation of the RT9605A as
a function of frequency and load capacitance. The value of
the CU and CL are the same and the frequency is varied
from 100kHz to 1MHz.
+12V
PHASEX
The operating junction temperature can be calculated from
the power dissipation curves (Figure 5). Assume
VDD = 12V, operating frequency is 200kHz and the
LGATEX
VCORE
CU=CL=1nF which emulate the input capacitances of the
high side and low side power MOSFETs. From Figure 5,
Figure 6. Waveforms at High Side MOSFET Shorted
the power dissipation is 100mW. For RT9605A, the Please note that the +12V trigger point to RT9605A is at
package thermal resistance θJA is 67°C/W, the operating
junction temperature is calculated as :
3V, and the clamped level on PHASE pin is at about 2.4V.
Obviously since the PHASE pin voltage increases during
TJ = (67°C/W x 100mW) + 25°C = 31.7°C
where the ambient temperature is 25°C.
(11) initial start-up, the VCORE increases correspondingly, but
it would quickly drop-off following the voltage in LGATE
and +12V.
All brandname or trademark belong to their owner respectively
DS9605A-05 August 2007
www.richtek.com
11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet RT9605A.PDF ] | |
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