Rainbow Electronics MAX1855 - Manual (Page 16)

MAX1716/MAX1854/MAX1855
High-Speed, Adjustable, Synchronous Step-Down
Controllers with Integrated Voltage Positioning
16 ______________________________________________________________________________________
Figure 2. Functional Diagram
REF
-10%
FROM
OUT
REF
7R R
D0
ERROR
AMP
TOFF
TON
REF
+10%
CHIP
SUPPLY
x2
SHDN
VPS
CC
VGATE
* NO OVERVOLTAGE PROTECTION ON THE MAX1854
D1 D2 D3 D4
ON-TIME
COMPUTE
TON
1-SHOT
1-SHOT
TRIG
IN
2V TO 28V
TRIG
Q
Q
S
R
2V
REF
R-2R
DAC REF
REF
PGND
+5V
OUTPUT
CS
DL
CS
V CC
V DD
LX
ZERO CROSSING
CURRENT
LIMIT
DH
BST
9R
R
I LIM
+5V
+5V
Q
SKIP
TON
V+
Σ
MAX1716
MAX1854
MAX1855
S
R
Q
OVP/UVP
DETECT
*
200k gm
FB
TON SETTING
(kHz)
K-FACTOR
( µs)
APPROXIMATE
K-FACTOR ERROR (%)
MIN RECOMMENDED V BATT AT
V OUT = 1.6V (V)
200 5 ±9 2.04
300 3.3 ±11 2.28
400 2.2 ±15 2.84
550 1.8 ±20 3.55
Table 3. Approximate K-Factor Errors