Datasheet

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FUNCTIONAL BLOCK DIAGRAMS
CURRENT
LIMIT
PWM
PWM
DRIVE
LOGIC
CURRENT
SENSE
3V3Regulator
and
Reference
UVLO
14 VDD
15
NC
16
NC
13
12
11
10
PVDD
OUT1
OUT2
PGND
4
5
3
3V3
ISET
AGND
8
ILIM
7
CLF
6
CTRL
2
CLK
1
NC
9
CS
TERMINAL FUNCTIONS
UCD8220
SLUS652D – MARCH 2005 – REVISED OCTOBER 2006
Figure 4. UCD8220
PIN NUMBER
UCD8220
PIN NAME I/O FUNCTION
HTSSOP-16 QFN-16
(PWP) (RSA)
Clock. Input pulse train contains operating frequency and maximum duty cycle limit. This pin is a
high impedance digital input capable of accepting 3.3-V logic level signals up to 2 MHz. There is
CLK 2 16 I
an internal Schmitt trigger comparator which isolates the internal circuitry from any external
noise.
Current limit flag. When the CS level is greater than the ILIM voltage minus 25 mV, the output
driver is forced low and the current limit flag (CLF) is set high. The CLF signal is latched high
CLF 7 5 O
until the device receives the next rising edge on the CLK pin. This signal is also used for the
start-up handshaking between the Digital controller and the analog controller
Pin for programming the current used to set the amount of slope compensation in Peak-Current
ISET 4 2 I
Mode control or to set the internal capacitor charging in voltage mode control.
Regulated 3.3-V rail. The onboard linear voltage regulator is capable of sourcing up to 10 mA of
3V3 3 1 O
current. Place 0.22 µ F of ceramic capacitance from this pin to analog ground.
AGND 5 3 - Analog ground return
Current limit threshold set pin. The current limit threshold can be set to any value between 0.25
ILIM 8 6 I
V and 1.0 V. The default value while open is 0.5 V.
Input for the error feedback voltage from the external error amplifier. This input is multiplied by
CTRL 6 4 I
0.5 and routed to the negative input of the PWM comparator
NC 1, 15, 16 7, 14, 15 - No connection.
Current sense pin. Fast current limit comparator connected to the CS pin is used to protect the
CS 9 8 I
power stage by implementing cycle-by-cycle current limiting.
PGND 10 9 - Power ground return. This pin should be connected close to the source of the power MOSFET.
OUT2 11 10 O The high-current TrueDrive™ driver output.
OUT1 12 11 O The high-current TrueDrive™ driver output.
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