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PDF RT9605B Data sheet ( Hoja de datos )
| Número de pieza | RT9605B | |
| Descripción | Triple-Channel Synchronous-Rectified Buck MOSFET Driver | |
| Fabricantes | Richtek Technology Corporation | |
| Logotipo |  |
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®
RT9605B
Triple-Channel Synchronous-Rectified Buck MOSFET Driver
General Description
The RT9605B 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 RT9605B can
efficiently switch power MOSFETs at frequency 300kHz
typically. Operating in higher frequency should consider
the thermal dissipation carefully. Each driver of RT9605B
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 RT9605B 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 RT9605B comes
to a small footprint package with VQFN-24L 4x4 package.
Ordering Information
RT9605B
Package Type
QV : VQFN-24L 4x4 (V-Type)
(Exposed Pad-Option 1)
Note :
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
Z : ECO (Ecological Element with
Halogen Free and Pb free)
Richtek 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.
Features
Drive Six N-MOSFETs for 3-Phase Buck PWM Control
Adaptive Shoot-Through Protection
Support High Switching Frequency
Fast Output Rising/Falling Time
Propagation Delay 40ns
Tri-State Input for Bridge Shutdown
Upper MOSFET Direct Short Protection
Small 24-Lead VQFN Package
RoHS Compliant and 100% Lead (Pb)-Free
Applications
CPU Core Voltage Supplies on Motherboard
High Frequency Low Profile DC/DC Converters
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.
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
14 LGATE3
GND 6
13 GND
7 8 9 10 11 12
VQFN-24L 4x4
Copyright ©2014 Richtek Technology Corporation. All rights reserved.
DS9605B-04 May 2014
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
1 page  
RT9605B
Parameter
Symbol
PWM Threshold
Output
VPWMRTH
VPWMFTH
UGATE Rise Time
UGATE Fall Time
LGATE Rise Time
LGATE Fall Time
UGATE Turn-Off Propagation Delay
LGATE Turn-Off Propagation Delay
Shutdown Window
tRUGATE
tFUGATE
tRLGATE
tFLGATE
tPDUGATE
tPDLGATE
Test Conditions
PWM_IN Rising
PWM_IN Falling
PVCC = 12V, 3nF load
PVCC = 12V, 3nF load
PVCC = 12V, 3nF load
PVCC = 12V, 3nF load
PVCC = 12V, 3nF load
PVCC = 12V, 3nF load
Min Typ Max Unit
2.7 3.1 3.5
V
0.8 1 1.3 V
-- 80 -- ns
-- 40 -- ns
-- 40 -- ns
-- 25 -- ns
-- 30 -- ns
-- 25 -- ns
0.8 -- 3.5 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. 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.
Note 3. Devices are ESD sensitive. Handling precaution recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
DS9605B-04 May 2014
All brandname or trademark belong to their owner respectively
www.richtek.com
5
5 Page 
RT9605B
10
12V
1µF
PWM
1N4148
1µF
CBOOTx
BOOTX
VDD UGATEX
RT9605B
PHASEX
PWMX LGATEX
GND
12V
2N7002
CU
3nF
2N7002
CL
3nF
20
Figure 3. Test Circuit (One Phase is Shown)
Over Voltage Protection Function at Power On
An unique feature of the RT9605B is the addition of over
voltage protection in the event of upper MOSFET direct
shorted before power on. The RT9605B 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 5 shows the measured waveforms with the high
side MOSFET directly shorted to 12V.
Figure 4 shows the power dissipation of the RT9605B 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.
The operating junction temperature can be calculated from
the power dissipation curves (Figure 4). Assume
VDD = 12V, operating frequency is 200kHz and the
CU=CL=1nF which emulate the input capacitances of the
high side and low side power MOSFETs. From Figure 4,
the power dissipation is 100mW. For RT9605B, the
package thermal resistance θJA is 67°C/W, the operating
junction temperature is calculated as :
TJ = (67°C/W x 100mW) + 25°C = 31.7°C
where the ambient temperature is 25°C.
(11)
The method to improve the thermal transfer is to increase
the PC board copper area around the RT9605B 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 4. Power Dissipation vs. Frequency
+12V
PHASEX
LGATEX
VCORE
Figure 5. Waveforms at High Side MOSFET Shorted
Please note that the +12V trigger point to RT9605B is at
3V, and the clamped level on PHASE pin is at about 2.4V.
Obviously since the PHASE pin voltage increases during
initial start-up, the VCORE increases correspondingly, but
it would quickly drop-off following the voltage in LGATE
and +12V.
Layout Consideration
Figure 6 shows the schematic circuit of a two-phase
synchronous buck converter to implement the either phase
of RT9605B. The converter operates at VIN 12V.
L1
1.2µH
VIN
12V
VCORE
C3
1500µF
12V
C1
1000µF
Q1
L2
2µH
Q2
R1
10
C4
1µF
D1
C2
1µF
CB BOOTX PVCCX
1µF
UGATEX PWMX
PHB83N03LT PHASEX
PHB95N03LT LGATEX GND
PWM
Figure 6. Sync. Buck Converter Circuit
DS9605B-04 May 2014
All brandname or trademark belong to their owner respectively
www.richtek.com
11
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet RT9605B.PDF ] | |
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