Gateway FPD 1500 - Pin Configuration

PIN NAME FUNCTION
1 CS3 Current-sense input for +3.3V; +100mV = current limit level referenced to FB3.
2 SS3 Soft-start input for +3.3V. Ramp time to full current limit is 1ms/nF of capacitance to GND.
3 ON3 ON/ OFF control input disables the +3.3V PWM. Tie directly to VL for automatic start-up.
4 D1 #1 level-translator/comparator noninverting input, threshold = +1.650V. Controls Q1. Tie to GND if unused.
5 D2 #2 level-translator/comparator noninverting input (see D1)
6 VH External positive supply-voltage input for the level translators/comparators
7Q2
#2 level-translator/comparator output. Sources 20µA from VH when D2 is high. Sinks 500µA to GND
when D2 is low, even with VH = 0V.
8 Q1 #1 level translator/comparator output (see Q2)
9 GND Low-current analog ground
10 REF 3.3V reference output. Sources up to 5mA for external loads. Bypass to GND with 1µF/mA of load or
0.22µF minimum.
11 SYNC
Oscillator control/synchronization input. Connect to VL or GND for 200kHz; connect to REF for
300kHz. For external clock synchronization in the 240kHz to 350kHz range, a high-to-low transition
causes a new cycle to start.
12
SHDN
Shutdown control input, active low. Tie to VL for automatic start-up. The 5V VL supply stays active in
shutdown, but all other circuitry is disabled. Do not force SHDN higher than VL + 0.3V.
13 ON5 ON/ OFF control input disables the +5V PWM supply. Tie to VL for automatic start-up.
14 SS5 Soft-start control input for +5V. Ramp time to full current limit is 1ms/nF of capacitance to GND.
15 CS5 Current-sense input for +5V; +100mV = current-limit level referenced to FB5.
16 DH5 Gate-drive output for the +5V high-side MOSFET
17 LX5 Inductor connection for the +5V supply
18 BST5 Boost capacitor connection for the +5V supply (0.1µF)
19 DL5 Gate-drive output for the +5V low-side MOSFET
20 PGND Power ground
21 FB5 Feedback and current-sense input for the +5V PWM
22 VL 5V logic supply voltage for internal circuitry. VL is always on and can source 5mA for external loads.
23 V+ Supply voltage input from battery, 5.5V to 30V
24 DL3 Gate-drive output for the +3.3V low-side MOSFET
25 BST3 Boost capacitor connection for the +3.3V supply (0.1µF)
26 LX3 Inductor connection for the +3.3V supply
27 DH3 Gate-drive output for the +3.3V high-side MOSFET
28 FB3 Feedback and current-sense input for the +5V PWM
PIN CONFIGURATION
PIN CONFIGURATION
MAX785 Dual-Output Power-Supply Controller
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28
27
26
25
24
23
22
21
1
2
3
4
5
6
7
8
FB3
DH3
LX3
BST3
D1
ON3
SS3
CS3
DL3
V+
VL
FB5
Q1
Q2
VH
D2
20
19
18
17
9
10
11
12
PGND
DL5
BST5
LX5
SHDN
SYNC
REF
GND
16
15
13
14
DH5
CS5
SS5
ON5
1
28