Datasheet
SLUS564C − JULY 2003 − REVISED OCTOBER 2008
8
www.ti.com
TERMINAL FUNCTIONS (continued)
TERMINAL
I/O
DESCRIPTION
NAME NO.
I/O
DESCRIPTION
PGOOD 12 O
Power good output. This is an open drain pull-down pin for power good. It remains low during soft-start until
both outputs become within ±7.5%. If INV1 or INV2 is out of regulation, or VREG5V goes under UVLO then this
pin goes low. The internal delay timer counts 2048 clks at low to high (by design, no delay for high to low). If
ENBLx is low, and the power good output is high, then the power good signal for that channel is ignored.
REF_X 8 O
10-V N-channel MOSFET bias or (VO1_VDDQ)/2 reference output. If dual mode is selected (DDR > 2.2 V)
then this pin provides a low 10-V current (< 2 mA) bias, dropped down from V
IN
, for the SO – S5 switched
N-channel MOSFETs. If DDR mode is selected (DDR
= GND) then this pin becomes (VO1_VDDQ)/2 capable
of 3 mA source current. This bias/reference is shut off when ENBL1 and ENBL2 are both low. (See Table 2)
REG5_IN 21 I
External 5V regulator Input. If this pin is above 4.7 V, then the 5 V circuit bias switches from the VREF5 to the
supply presented to REG5_IN.
SSTRT1 3 I
Soft-start/frequency select input. Connect a capacitor between SSTRTx and ground for adjusting the softstar
t
time. A constant current fed to this capacitor ramps the reference during startup. Frequency selection is de-
SSTRT2 13 I
time. A constant current fed to this capacitor ramps the reference during startup. Frequency selection is de-
scribed in Table 1. The soft-start capacitor is discharged upon UVLO/OVP/UVP, or when ENBLx is asserted
low.
SKIP 4 I
Skip mode selection pin. Ground for automatic control between PWM mode in heavy load and hysteretic op-
eration in light load. Tie high for PWM only operation for the entire load condition. If DDR
is grounded, then skip
mode is disabled for Channel 2.
TRIP1 25 I
Channel 1 overcurrent trip point voltage input. Connect a resistor between TRIP1 and the high-side N-channel
MOSFET input conversion voltage for high-side N-channel MOSFET UVP current limit shut down. Connect
resistor between TRIP1 and GND for low-side N-channel MOSFET overcurrent latch shutdown.
TRIP2 23 I
Channel 2 overcurrent trip point voltage input. Connect a resistor between TRIP2 and the high-side N-channel
MOSFET input conversion voltage for high-side N-channel MOSFET UVP current limit shut down with a 180°
channel phase shift. Connect resistor between TRIP2 and GND for low-side N-channel MOSFET over current
latch shut-down. The oscillator voltage ramp adjustment (the feed-forward feature) for channel 2 is disabled
when this pin is tied to ground via a resistor.
VBST1 30 I
Supply Input for high-side N-channel FET driver. Typically connected via charge pump from LLx.
VBST2 16 I
Supply Input for high-side N-channel FET driver. Typically connected via charge pump from LLx.
VO1_VDDQ 5 I
Output discharge pin. Connect this pin to the SMPS output. The output is discharged to at least 0.3 V before
the channel can start-up again. If DDR is low, then the VO1_VDDQ pin must be connected to the VDDQ output
VO2
11 I
the channel can start-up again. If DDR is low, then the VO1_VDDQ pin must be connected to the VDDQ output
since this pin works as the VDDQ feedback to generate the VTT reference voltage and VO2 should be con
-
nected to GND since V
TT
must remain in a high-impedance state during S3 mode.
VREG5 22 O Internal, 60-mA, 5-V regulator output. DDR, ENBL1 or ENBL2 high ( > 2.2V) turns on the 5 V regulator.
VIN 24 I
High-voltage input. Typically the battery voltage. This pin serves as inputs for the VREF5 regulator, the REF_X
regulator and positive input for overcurrent comparators. Precaution should be taken for tracing between this
pin and the high-side N-channel MOSFET drain where positive node of TRIPx resistors are located.
Table 2. Reference Regulator Control
MODE DDR ENBL1 ENBL2 VREF5 REF_X OSC
DDR LOW LOW LOW OFF OFF OFF
DDR LOW LOW HIGH ON
OFF
ON
DDR LOW HIGH LOW ON
VO1_DDR
2
ON
DDR LOW HIGH HIGH ON
VO1_DDR
2
ON
DUAL HIGH LOW LOW ON OFF OFF
DUAL HIGH LOW HIGH ON 10 V ON
DUAL HIGH HIGH LOW ON 10 V ON
DUAL HIGH HIGH HIGH ON 10 V ON