Datasheet

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
SLUS564C − JULY 2003 − REVISED OCTOBER 2008
6
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ELECTRICAL CHARACTERISTICS (continued)
T
A
= −40°C to 85°C, 4.5 V < V
IN
< 20 V, C
VIN
= 0.1 µF, C
VREG5
= 2.2 µF, C
REF_X
= 0.01 µF, PGOOD = 0.2 V, ENBLx = DDR = VIN,
INVx = COMPx, RSSTRTx = OPEN, TRIP1 = TRIP2 = VIN, LLx = GND, VBSTx = LLX+5, C
(OUTx_U, OUTx_D)
=1 nF, REG5_IN = 0V, GND =
OUTGNDx = 0 V, VO1_VDDQ = VO2 = 0 V (unless otherwise stated)
PARAMETER
TEST CONDITIONS MIN TYP MAX UNIT
TIMERS: SOFT-START RAMP GENERATOR
I
SSQ
SSTRTx charge current V
SSTRTx
= 1 V 1.8 2.3 2.9 µA
I
SSDQ
SSTRTx discharge current V
SSTRTx
= 0.5 V 0.1 mA
V
REFTRK
SSTRTx at SMPS regulation point voltage
(7)
1.00 1.22 1.45
V
SSOK
SSTRTx OK to restart voltage 0.23 0.29 0.35
V
V
SSFIN
SSTRTx finished voltage
(8)
1.4 1.5 1.6
V
V
SSCLP
SSTRTx frequency select voltage
(9)
3.35 3.60 3.80
OUTPUTS: INTERNAL BST DIODE
V
FBST
Forward voltage
(V
VREF5
− V
VBSTx
), V
VREF5
= 5 V, I
F
= 10 mA
T
A
= 25°C
0.80 0.85 V
I
RBST
Reverse current V
RBST
= 30 V 0.1 0.5 µA
OUTPUTS: N-CHANNEL MOSFET GATE DRIVERS
R
USRC
OUTx_U source impedance 3 10
R
DSRC
OUTx_D source impedance 3 10
Ω
R
USNK
OUTx_U sink impedance 2.5 5.0
Ω
R
DSNK
OUTx_D sink impedance 2.5 5.0
T
DEAD
Gate non-overlap dead time 100 ns
(1)
Ensured by design. Not production tested.
(2)
Maximum 450-kHz frequency can be achieved only when both channels are enabled.
(3)
270 kHz is the default frequency during start-up for both channels.
(4)
See Table 1.
(5)
See PWM detailed description
(6)
Feedforward Gain can be approximated as follows:
V
RAMP
= K1×V
IN
+B1, V
OFFSET
=K2×V
IN
×+B2 where K1=0.017, K2=0.01, B1=0.35 V, B2=0.4 V.
At the running duty cycle, the V
COMP
should be approximately: V
COMP
+ V
OUT
ǒ
K1 )
B1
VIN
Ǔ
)
(
K2 VIN ) B2
)
(7)
See waveform point A in Figure 1
(8)
See waveform point B in Figure 1
(9)
See waveform point C in Figure 1
Table 1. Frequency Selection
SSTRT1 SSTRT2 FREQUENCY (kHz)
C
SSTRT
only C
SSTRT
only 450
(10)
1 MΩ || C
SSTRT
to GND C
SSTRT
only 360
C
SSTRT
only 1 MΩ || C
SSTRT
to GND 360
1 MΩ || C
SSTRT
to GND 1 MΩ || C
SSTRT
to GND 270
(10)
Although selection is made by placing a 1M resistor in parallel with the SSTRTx timing
capacitor, the softstart time to 0.85V is altered by about only 20%.